Plumbing Systems Advanced

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ADVANCED PLUMBING SYSTEMS


PSD 136

Animal-care Facility Piping Systems

Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson

NOVEMBER/DECEMBER 2006

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CONTINUING EDUCATION

Animal-care Facility Piping Systems


INTRODUCTION This chapter discusses various piping systems uniquely associated with the physical care, health, and well-being of laboratory animals. Included are various utility systems for animal watering, water treatment, room and floor cleaning, equipment washing, cage flushing and drainage, and other specialized piping required for laboratory and experimental work within the facility. Other systems involved with general laboratory and facility work, such as those for compressed gases and plumbing, are discussed in their respective chapters.

General It is expected that a facility involved with long-term studies will have different operating and animal drinking-water quality requirements than one used for medical research. For critical studies, the various utility systems shall incorporate design features necessary to ensure reliability and provide a consistent environment. As many variables as are practical (or desirable) shall be eliminated to ensure the accuracy of the ongoing experiments being conducted. Regardless of the facility type, different users and owners have individual priorities based on experiences, operating philosophies, and corporate cultures that must be established prior to the start of the final design phase of a project.

Codes and Standards

1. The local codes applicable to plumbing systems must be observed in the design and installation of ordinary plumbing fixtures and potable water and drainage lines for the facility. 2. 10-CFR-58 is the code (by the agencies of the federal government) for good laboratory practice for nonclinical laboratory studies. 3. 21-CFR-211, cGMP, requires compliance with FDA protocols for pharmaceutical applications. 4. NIH publication 86-23, Guide for the Care and Use of Laboratory Animals. 5. American Association for Accrediation of Laboratory Animal Care (AAALAC). Inspection and accreditation by the AAALAC is accepted by the NIH as assurance that the facility is in compliance with Public Health Services (PHS) standards.

Animal Drinking-Water Systems The purpose of the animal drinking-water system is to produce, distribute, and maintain an uninterruptible supply of drinking water with a specific and consistent range of purity to all animals in a facility. There are two general types of systems: an automated central-distribution system and individual water bottles.

System Types The great majority of animals used by laboratories for medical and product research are mice, rats, guinea pigs, rabbits, cats, dogs, and primates. Smaller animals and primates are kept in stacked cages, often on racks. Medium-sized animals, such as dogs, goats, and pigs, are kept in kennels or pens. Larger floor areas are required for barnyard animals such as cows. Watering can be done either by an automatic, reduced-pressure, central system, which pipes water from the source directly to each cage, kennel or pen; or by separate drinking bottles or watering devices manually placed in individual cages or pens. Automated, Central Supply-and-Distribution System The purpose of an automated, central, drinking-water supply system is to automatically treat and distribute drinking water. Ancillary devices are used to flush the system and maintain a uniform and acceptable level of purity. The system consists of a raw or treated water source, a purification system, medicinal and disinfection injection equipment if necessary, pressure-reducing stations, and a distribution piping network consisting of a low-pressure room-distribution piping system and a rack-manifold pipe terminating in a drinking valve for each cage or pen for the animals. Also necessary is an automated flushing system for the room-distribution piping activated by a flush-sequence panel, and a monitoring system to automatically provide monitoring of such items as drinkingwater pressure, flow, and possible leakage. Animals in cages are kept in animal rooms. Cages are usually placed in multi-tiered, portable or permanent cage racks, which contain a number of cages. The cage rack has an integral piping system installed, called a “rack manifold,” that distributes the water to all cages. The rack manifold could be installed by the manufacturer or in the facility by operating personnel. The rack manifold receives its water from the room-distribution piping. The connection between the room-distribution piping and the rack manifold is made by means of a detachable recoil hose generally manufactured from Polypropylene (PP), nylon, or Ethylene-Propylene Diene Monomer (EPDM). This hose is flexible, generally 3⁄8 in. (12 mm) in size and coiled to conserve space. It will stretch to a length of about 6 ft 0 in. (2 m). Each end is provided with a quick-disconnect fitting used to attach the hose to both the room-distribution piping and the rack manifold. To maintain drinking-water quality, a method of flushing the room-distribution piping and the rack manifold shall be provided. Ancillary equipment includes flushing and sanitizing systems to wash the recoil hose and the cage rack-piping interior. Water Bottles Drinking water bottles are individual units with an integral drinking tube that are placed by hand on a bracket in each cage.

Reprinted from Pharmaceutical Facilities Plumbing Systems, Chapter 7: “Animal-care Facility Piping Systems,” by Michael Frankel. © American Society of Plumbing Engineers. Plumbing Systems & Design


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These bottles could be filled either by hand or automatically via the operating cost of the proposed system, the species of aniSimpo PDF Merge and Split Unregistered Versionmals - http://www.simpopdf.com a bottle filler. housed in the facility, and the animal-housing methods. Automatic bottle fillers should be considered to reduce the The overall objective is to eliminate as many variables as postime necessary to fill bottles and minimize water spillage. Bottle sible for the entire period of time the studies or experiments are fillers are available with manifolds to fit any size bottles. They conducted. can be supplied with purified water from a central water supply The most often-used treatment for drinking water is reverse and—with separate, programmable proportioners—could osmosis. Other possible treatment methods are distillation acidify, chlorinate, and medicate the water as required. The and deionization. A discussion of these purification methods bottle filler automates the filling procedure so that the bottles appears in the chapter “Water Systems.” are correctly positioned during filling and stops the flow when Reverse Osmosis the water reaches a predetermined level. When a higher-quality water is required and other types of puriFlushing System In order to maintain drinking-water quality, the drinking-water distribution system should be flushed periodically. This is accomplished by having the same drinking water that is normally distributed to the animals flow through the piping system at an elevated flow rate, pressure, and velocity. The water is sent to drain and not recovered. This is initiated automatically at the drinking-water pressure-reducing station by the addition of separate regulating valves and pressure-regulating arrangements. Different flushing arrangements are possible, depending on the cost, facility protocol, and purity desired. One method flushes only the main runs by the addition of a solenoid valve at the end of the main run and the provision of a return line to drain from this point. Another method is to flush the mains and the room-distribution piping by adding the solenoid valve at the end of each room-distribution branch with the return line to drain from each room. A third method flushes the entire system, including the rack manifold, by adding a solenoid valve on each cage connection to the room-distribution pipe, which flushes the recoil hose and the rack manifold. It is accepted practice to replace all the drinking water in the room-distribution piping system at regular intervals, a minimum of twice daily. To approximate the amount of water in the pipe, allow 1 gal (4 L) for each 33 ft 0 in. (10 m) of pipe. General practice is to flush the system with water at about 15 psi (90 kPa) at a rate of 15 gpm (60 L/min). If the drinking water is not purified, it is recommended that the piping be flushed at least twice daily for about 2 min. For purified water, flush once daily for about 1 min. Flushing can be done manually by means of a valve in the pressure-reducing station enclosure or automatically by the addition of a bypass and solenoid valve around the low-pressure assembly to the pressure-reducing station. The sequence and duration of the automatic flush cycle is controlled from a flush-sequencer panel. Figure 7-1

fied water are not available in a facility, reverse osmosis (RO) is normally selected. Since the amount of water is usually small, a package type unit mounted on a skid is provided and connected directly to the water supply. The RO system is flexible and, when used in combination with DI water supply, will provide water that is virtually contamination free. Disinfection and Medication of Drinking Water Disinfection chemical mixtures are added to the animal drinking-water supply to eliminate and control bacterial contamination in the central and room-distribution piping system. Medication is added to conform with experimental protocols if necessary. These mixtures are usually introduced into the piping system by a self-contained, central, proportioning (injector) unit using facility water pressure. Medication is added to the drinking water using the same proportioning equipment that adds disinfectant. All equipment is available in a wide range of sizes and materials. A schematic detail of a typical central proportioner is illustrated in Figure 7-1. Chlorination Chlorination is a recognized biocidal treatment that leaves a residual of chlorine in the entire central-distribution system. Hyperchlorinated water is not as corrosive as acidified water and could be used with brass/copper distribution system components. Accepted practice is to provide a pH higher than 4, with a residual range of free chlorine between 5 and 12 ppm. Free chlorine in water dissipates in time with light, heat, and reaction with organic contaminants, making it ineffective when water bottles are used. Chlorine creates toxic compounds in reaction with some water contaminants and medications. Acidification Acidification has an advantage over chlorination in that it is more stable and lasts longer in the system. The disadvantage is that corrosion-resistant materials must be used. The pH range should be between 2.5 and 3 in order to be effecTypical Central Proportioning Unit

Drinking-Water Treatment Systems The purpose of the drinking-water treatment system is to remove impurities from the raw-water supply to achieve the water quality required by the animals in the facility. In addition, disinfectant and medication can be added to the water during treatment if required. Systems Description There are no generally recognized and accepted standards for animal drinking-water quality. Purity and consistency requirements depend on the incoming water quality, the established protocol of the end user, the importance of either the initial or NOVEMBER/DECEMBER 2006

Plumbing Systems & Design

CONTINUING EDUCATION: Animal-care Facility Piping Systems tive. A pH lower than 2.5 will cause the water to become “sour” Simpo PDF Merge and Split Unregistered Version and the animals will not drink it. At a pH above 3, the mixture is not considered an effective germicide.

Figure 7-2 Reverse “S” Configuration Watering Manifold - http://www.simpopdf.com

Drinking-Water System Components and Selection Pressure-Reducing Station The pressure-reducing station reduces the normal pressure of the raw-water supply to a level required for the animal-room drinking-water distribution system. As an option, a secondary system can be added to provide a higher pressure in the roomdistribution system for flushing. The pressure and flow rate depend on the type and number of animals to be supplied. Also usually included are a 5-µ water filter, a pressure gauge, and a backflow preventer. Timing devices that automatically control flushing duration are controlled by a remote flush-sequencer panel, which controls all flushing sequencing operations. The recommended pressures for animal-room piping distribution to various animals are as follows: 3-5 psig (20.4-34 kPa) 3-5 psig 3-5 psig 6-12 psig (41-81.6 kPa)

The secondary pressure-reducing assembly used to provide automatically room-distribution pipe-flushing water operates at a pressure of 15 psig (102 kPa). This assembly is installed as a bypass around the low-pressure assembly. Manual operation at a lower cost could also be provided. This additional pressure for a short period of time will not cause the animals any difficulty if they decide to drink during the flushing cycle. One pressure-reducing station can be connected to as many as 35 interconnect stations to small animal-rack manifolds, often referred to as “drops.” This allows 1 station to control more than 1 animal room. The pressure-reducing station is a preassembled unit complete with all the various valves, fittings, and reducing valves required for a specific project. All the components are installed in a cabinet, which requires only mounting and utility connections. Drinking Valves Drinking valves are used by the animals to obtain water from the distributionsystem piping. An internal mechanism keeps the valve normally closed; the animal drinking from the valve must open it by some action, such as moving the entire valve or operating a small lever inside the body of the valve with the tongue. Many different kinds of valve are available to supply any type of animal that may be kept in the facility. The valves can be mounted on cages, on the rack manifold, or on the walls of pens and kennels at varying heights with the use of special brackets.


Animal-Rack Manifold Configurations The configuration of the piping on the animal rack plays an important part in the effectiveness and efficiency of the filling and flushing of the drinking-water system. The two most oftenused configurations are the reverse “S” and the “H.” The reverse “S,” illustrated in Figure 7-2, is the most often-used configuration. It has two basic styles based on the valve location in the flush drain line. One style has a supply control valve at the top and the other has a drain valve at the bottom. Either location is acceptable, with the deciding factor being the ease of operating the valve where the rack is installed. This configuration has the advantage of eliminating dead legs and offers more convenience to facility personnel when they fill the piping after washing. The vent is a manually operated air bleed used when the cage rack is reconnected to the room-distribution pipe. It is opened until water is discharged, thereby eliminating any air pockets in the manifold. This manifold style provides a positive exchange of water during flushing with a minimum usage of time and water.

Figure 7-3 Typical Room Distribution, On-Line, Rack Manifold Flushing System


Source: Courtesy of Edstrom Industries.

Small animals, such as Rats and mice Primates Dogs and cats Swine and piglets

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This configuration is used far more than any The pipe sizes in other areas of the Figure 7-4 Standard “S” Configuration Manifold Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com other manifold style. It is easily converted animal facility are determined based on to automatic flushing by the installation of the requirements of maximum flow rate at solenoid devices on the valve. It is recomthe necessary pressure to supply the flushmended when micro-isolator cage systems ing velocity. Maximum flow rate depends are installed. The complete, on-line, rackon the flush sequencing, and the pressure manifold flushing system is illustrated in drop depends on overcoming pressure Figure 7-3. This cage system has the advanloss through the equipment connected to tage of the complete isolation of individual the branch being sized—such as pressurecages, with the accompanying capability reducing stations, solenoid valves, and for additional flushing and disinfection of recoil hoses—and friction loss through the the piping system. piping network. Allowance must be made One variation of the reverse “S” is the to provide a sufficiently high flow rate and standard “S,” illustrated in Figure 7-4. This water velocity to efficiently provide the configuration has the advantage of comflushing action desired. plete on-line flushing and lower initial cost Cleaning and Drainage Systems of the manifold. Disadvantages are the and Practices need for extra supports on the cage rack General and the need for venting to be done manKeeping the animal rooms and cages ually or by the animals after being placed clean is an extremely important facet of facility practice. The in service. This configuration is no longer recommended. The “H” style, illustrated in Figure 7-5, although rigidly cleaning of the animal room is accomplished either by sponging installed and with positive venting, is not suitable for on-line the walls, floors, and ceiling or by hosing down the room. Cage flushing. Because of this, it is rarely used except for larger ani- racks can be cleaned by washing them with a hose or by placing mals, which will consume all the water in the rack piping mani- them in a large washing machine. Cages are cleaned in a cage washer. Pens and kennels are hosed down. Floors in pens are fold. The most common piping materials are CPVC and 304L stain- cleaned with hoses and the bedding with feces is pushed into less steel. CPVC conforms to ASTM D 2846, is 0.875 outside trenches with floor drains. In specialized areas, such as holding or isolation rooms where diameter (OD) with 0.188 in. minimum wall thickness. Joining process is done with solvent cement socket joints. The drinking only small animals are kept, it is common practice to have pervalves are installed with a proprietary, drilled and tapped fit- manent cage racks or have the portable racks remain in the ting. The 304L stainless steel tubing is 0.50 OD with a 0.036 in. animal room. The litter is put into bags and brought to other minimum wall thickness. Fittings are made with O-ring joints areas for disposal. The cage racks are manually wiped down and socket fittings or compression type fittings. The mounting of and no rack washer is required. A sink is usually provided in both pipe materials is accomplished by the use of 304 SS stain- the animal room for the convenience of the cleaning personnel. Individual water bottles, if provided, could be washed in the less-steel clamps and fasteners. sink. The cages are removed and washed separately in a cage System Sizing Methods washer. This type of animal room usually does not require a The water consumption of small animals in cages is very low. floor drain if the entire room will be sponged down. If hosing is It is also probable that the animal room will not be used to full practiced, a floor drain is required. capacity. Because of this low consumption flow rate, the flushRabbits and guinea pigs have a tendency to spray urine and ing-water flow rate of the system is the critical factor in sizing feces. This requires that the racks be hosed down in the room. A the piping. Typically, the animal-room piping distribution netwash station with a hose reel and detergent injection capability work is a header uniformly sized at ½ in. (50 mm) throughout to hose down the cage racks and the room itself is usually placed the animal room. in individual rooms. Citric acid is often used as a cleaning agent for rabbits. Figure 7-5 Standard “H” Configuration Manifold Hose Stations Hose stations usually consist of a mixing valve with cold water and steam to make hot water or hot water alone, a length of flexible hose, and an adjustable spray nozzle. Hot and cold water are also used. It can be exposed or provided with an enclosure when an easily cleaned surface is required. Cleaning-Agent Systems Cleaning agents are used to clean and/or disinfect the walls, ceiling, and floor of a room and to add agent to the cage wash water. When used to clean rooms, the equipment used for this purpose is commonly called a “facility detergent system.” When used to add agent to the cage washing water it is often called a “cage-washing detergent system.” These are separate systems and are not capable of providing agent to each other. NOVEMBER/DECEMBER 2006


CONTINUING EDUCATION: Animal-care Facility Piping Systems Figure 7-6 Single-Station Detergentand System Simpo PDF Merge Split

supply has to be changed. A typical central-supply deter-

Unregistered Version - http://www.simpopdf.com gent-dispensing system is illustrated in Figure 7-7.

The cage-washing detergent system is usually located in the wet area of the cage-washing facility and, with the use of a detergent pump, could be used as a central system to supply cage and bottle washers. A typical schematic detail of a cage-washing system is illustrated in Figure 7-8. It is common practice to have a central system or a wallmounted cleaning-agent dispenser unit along with the hose station. Separate, portable units could be used when cross contamination between animal rooms is a consideration. A typical, wall-mounted, cleaning-agent system consists of separate water and cleaning-agent tanks; a water pump; and a special, coaxial hose that sprays a proportioned mixture of the water and cleaning agent. Compressed air is often used to provide pressure. Cage-Flushing Water System The removal of animal waste from cages can be done by several methods. One method removes the waste along with the bedding at the time cages are removed from the animal room to be washed. Another method uses an independent rack-flush system to automatically remove animal waste from cages on racks while the animals and cages remain in the animal room. The independent rack flush is a separate system that uses chlorinated water automatically distributed to each animal room. The cages and racks are constructed so that the animal droppings fall through the cage floor onto a sloping pan below each tier of cages. Each tier is cascaded at the end onto the sloping pan below. Eventually, the lowest pan spills into a drain trough in the animal room. The flushing schedule is decided by facility personnel. The water supply could be a reservoir placed on the rack that is filled with water and automatically discharged onto the pans at preset intervals. These preset intervals are determined based on experience and generally range from once to three times daily. Another method uses a solenoid valve to automatically discharge water onto the pans; the valve is sequenced by a timer set to alternate fill and dump cycles. The timer could be either

A single-station detergent-dispensing system is used when rooms are cleaned with mops or squeegees. It consists of a wallmounted unit having a holder for detergent concentrate and an injector unit. A container filled with detergent concentrate is placed in the holder and is used to supply agent to the injector that dispenses a metered amount of agent when a hose bibb is opened to fill the pail or container. These rooms usually have sinks and mop racks inside to be used only for these rooms. A typical schematic detail of a single-station detergent system is illustrated in Figure 7-6. When used to supply a single or multiple-spray hose for cleaning floors and walls, a central system could be installed to supply several rooms within a facility by means of a detergent pump that dispenses agent. A 55-gal drum of agent should be used to reduce the number of times the Figure 7-8 Typical Cage-Washing Detergent System

Figure 7-7 Central-Supply Detergent System



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Figure 7-9 Typical Cage-Rack Utility Connections Simpo PDF Merge and Split Unregistered

disposed of as regular garbage. Regular gar-

Version - http://www.simpopdf.com bage disposal is the most common method of disposal. It involves collecting, moving, and storage of the waste into large containers until regular garbage collection is made. This is very labor intensive. Discharge into the drainage system must first be accepted by the local authorities and responsible code officials. This requires the bedding to be water soluble, that it shall not float, and provision be made to thoroughly mix the bedding with water. This mixture is called a “slurry.” Experience has shown, if done properly, discharge into an adequately sized drain line—minimum size 6 in. (150 mm)—has caused no problems, since the effluent has the same general characteristics of water. A self-contained waste-disposal system is available that is capable of disposing of animal bedding and waste. The system consists of a pulping unit to grind the waste into a slurry and sanitize it, a water extractor to remove most of the water from the slurry, and the interconnecting piping system that transports the slurry from the pulper to the extractor and recirculates the water removed from the extractor back to the pulping unit for reuse. The solid waste is removed as garbage. Manufacturers are available for assistance in the design and equipment selection for this specialized system. The system has the advantages of reducing water use, reducing operating costs by eliminating the handling of the waste by operating personnel, compacting the waste to about 20% of the space required for standard garbage not compacted, and reducing the possibility of contamination by isolation of the disposal equipment. The disadvantage is its high initial cost.

centrally located or installed separately in each animal room. Larger cages, such as those for primates, are usually stacked no more than two cages high. Current practice is to have these cages manually cleaned by personnel who hose down the pans directly into floor or wall troughs. Water is supplied to each cage rack by means of a recoil hose, which has a different quick-disconnect end than that of the drinking water recoil hose to avoid cross connection. Refer to Figure 7‑9 for a detail Figure 7-10 Typical Waste-Disposal System of a typical cage-rack utility connection arrangement. Solid-Waste Disposal Solid waste consists of bedding, feces, animal carcasses, and other miscellaneous waste, including straw and sawdust used for larger farm animals. Bedding comprises the largest quantity of this solid waste. It is necessary to determine the quantity of bedding before a decision can be made as to the most cost-effective method to dispose of it. Bedding can be disposed of by incineration, as regular garbage, or into the sewer system. Incinerators are costly, require compliance with many regulatory agencies and multiple permits, and often result in objections from adjoining property owners. Incineration is the preferred method of disposing of carcasses and large quantities of contaminated waste. Carcasses could also be autoclaved and



CONTINUING EDUCATION: Animal-care Facility Piping Systems This system could consist of single or multiple units of dif- Equipment Washing Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com ferent capacities. It requires water intermittently for pulping at Most facilities contain washing and sanitizing machines to wash the rate of about 10 to 30 gpm (63 to 190 L/min). Hose bibbs cages, cage racks, and bottles, if used. There are two commonly should be installed for washdown. The pipe should be sized for used types of cage washer: the batch type and conveyer (tunnel) a maximum velocity of 8 fps (1.75 m/s), with typical slurry lines type. Batch washers require manual loading and unloading and ranging between 2 and 4 in. (50 and 200 mm) and return lines are used where a small number of cages and racks are washed. generally 2 in. (50 mm) in size. The extractor discharges into a The conveyer type is similar to a commercial dishwasher, where drain that should be 4 or 6 in. (100 or 150 mm) depending on the cages and racks are loaded on a conveyer and automatically the flow. A typical schematic diagram of a multiple installation moved through the machine for the washing and sanitizing is illustrated in Figure 7-10. cycles. Room-Waste Disposal The rooms in which animals are kept must be designed to allow proper drainage practices and in accordance with the anticipated cleaning procedures of the facility. Floor drains, drainage trenches (or troughs) at room sides, adequate and consistent floor pitch to drains or troughs, and floor surfaces are all important considerations. There are several considerations to be taken into account in locating floor drains. Experience has shown that placing drains in the center of a room is not acceptable because it is difficult to hose solids down a drain in this location. Another reason is that the floor must be pitched to the drain and if a cage rack is defective, it should roll to the side of the room. The best location is in a corner or at the side. Floor drains without troughs can be considered if the floors will only be squeegeed rather than hosed down. They should also be considered in contagious areas where contamination between rooms must be avoided. Gratings must have openings smaller than the wheels of racks or cages. In rooms where washdown and cage-rack flushing are expected, the provision of a floor trough should be considered. Troughs are often provided at opposite ends of the room to minimize the amount of floor drop due to pitch. Accepted practice uses a minimum floor pitch of 1⁄8 in./ft of floor run. The floor is pitched to the troughs to facilitate cleaning and also to provide an easy method to dispose of waste generated from the rack-flush system. It is common practice to provide an automatic or manual trough-flushing system with nozzles or jets to wash down the trough sides and eliminate as much of the contamination remaining in the trough as possible. Wall troughs, similarly to roof gutters, are located at a higher elevation. This type of trough arrangement is sometimes provided in addition to or in lieu of floor troughs if the arrangement of elevated cages and racks make it an effective drainage method. Experience has shown that prefabricated drain troughs in floors are preferred over those built on the wall as part of the architectural construction. The floor troughs are drained by means of a floor drain placed in a low point at one end. The troughs are usually pitched at ¼ in./ft of run to the drain. The drain should be constructed of acidresistant materials and have a grate that can be easily removed. For small animal rooms where bedding is not disposed of in the room, a 4-in. (100-mm) drain is considered adequate. In most other locations, it is recommended that a 6-in. (150-mm) drain be provided. A flushing-rim type drain should be considered to flush all types of waste into the drainage system. Floor drains should have the capability of being sealed by the replacement of the grates with solid covers during periods when the room may not be in service. Plumbing Systems & Design


Equipment Sanitizing Maintaining drinking-water quality requires that the recoil hoses and rack manifolds be not merely washed but internally sanitized. This is most often done at the same time the cages are washed. Separate rack-manifold and recoil-hose flush stations are available for this purpose and are usually installed in the cage-wash area. Washing can be done manually or automatically. The hoses are flushed for 1 to 2 min with 4 gpm (16 L/min) of water. Chlorine is injected into the water by a chlorine-injection station (proportioner) set to deliver 10 to 20 ppm into the flush water. Ten scfm of oil-free compressed air at 60 psig is blown through the hoses to dry them. If chlorine is used as a disinfectant, a contact time of 30 min is recommended before evacuation and drying. Periodic sanitizing of the room-distribution piping system is required for maintaining good water quality. Sanitizing is done prior to system flushing. To accomplish this, a portable sanitizer is used to manually inject a sanitizing solution directly into the piping system. In order to do this, an injection port is required at the inlet to the pressure-reducing station. The portable sanitizer usually consists of a 20-gal (90-L) polyethylene tank with a submersible pump inside and a flexible hose used to connect the tank to the injection port. The disinfecting solution is a mixture of chlorine and water with 20 ppm of chlorine. The mixture should maintain a contact time in the piping of 30 to 45 min. Drainage-System Sizing As mentioned previously, for individual animal rooms where bedding is not disposed of in the drainage system, a 4-in. drain is acceptable. In general, a 6-in. drain is considered good practice. The size of the drainage system piping should be a minimum of 6 in., with a ¼-in. pitch when possible and the piping sized to flow ½ to 2⁄3 full in order to accommodate unexpected inflow.

Monitoring Systems The monitoring of various animal-utility systems is critical to keep within a range of values consistent with the protocol of the experiments being conducted at the facility. This is accomplished by a central monitoring system that includes many measurements from HVAC and electrical systems. For the animal drinking-water system, parameters such as water pressure, flow rates, leakage, pH, and temperature in various areas of the facility are helpful for maintenance, monitoring, and alarms.

Systems Design Considerations The amount of exposed piping inside any animal room should be minimized. The exception is the animal drinking-water system, which is usually exposed on the walls of the room. This piping should be installed using standoffs to permit proper cleaning of the wall and around the pipe. The piping material used for all systems should be selected with consideration given to the facility cleaning methods and PSDMAGAZINE.ORG

type of disinfectant. Where sterilization is required and cleaning Simpo PDF Merge and Split Unregistered Version very frequent, stainless-steel pipe should be considered. If insulation is used on piping, it should be protected with a stainless steel jacket to permit adequate cleaning. Pipe penetrations should be sealed with a high-grade, impervious, and fire-resistant sealant. Escutcheons should not be used because they allow the accumulation of dirt and bacteria behind them. ✺

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CONTINUING EDUCATION Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson

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The technical article you must read to complete the exam is located at www.psdmagazine.org. The following exam and application form also may be downloaded from the Web site. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

About This Issue’s Article The November/December 2006 Continuing Education article is “Animal-care Facility Piping Systems,” Chapter 7 of Pharmaceutical Facilities Plumbing Systems by Michael Frankel. This chapter discusses the various piping systems uniquely associated with the physical care, health, and wellbeing of laboratory animals. Included are utility systems for animal watering, water treatment, room and floor cleaning, equipment washing, cage flushing and drainage, and other specialized piping required for laboratory and experimental work within the facility. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Animal-care Facility Piping Systems” (PSD 136)

PSD 136

Do you find it difficult to obtain continuing education units (CEUs)? Through this special section in every issue of PS&D, ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status.

1. What comprises the largest solid waste item from animal cages? a. bedding, b. feces, c. carcasses, d. miscellaneous waste

c. is the guide for the care and use of laboratory animals d. is the code for good laboratory practice for non-clinical laboratory studies

2. This chapter discusses various piping systems uniquely associated with the physical care, health, and well-being of ___________. a. laboratory workers, b. laboratory animals, c. animal watering, d. cage cleaning

8. Select the true statement below. a. There are no generally recognized and accepted standards for animal drinking water. b. Drinking valves are not used by animals to obtain water from the distribution system. c. Water pressure, minimum and maximum, for the various animals to be served is mandated in the plumbing code. d. Reverse osmosis (RO) systems are inappropriate for animal drinking water systems.

3. A single-station detergent-dispensing system is used when rooms are ___________. a. hosed down b. cleaned with mops or squeegees c. cleaned with steam d. none of the above 4. To maintain drinking water quality, ___________. a. a water purification system must be designed b. the water system must be allowed to run continuously c. there must be chlorine injection d. the drinking water distribution system must be flushed periodically 5. Floor drains should not be placed ___________ where animals are kept. a. under cages in rooms b. in the center of the room c. at the back edge of cages in rooms d. none of the above 6. A pulping unit is used to ___________. a. separate water from solid waste b. determine the pH of the waste c. determine the temperature of the waste d. grind the waste into a slurry 7. 10-CFR-58 ___________. a. is the federal code that must be followed when keeping animals for research b. requires compliance with FDA protocols for pharmaceutical applications 10 Plumbing Systems & Design


9. The recommended water pressure for dogs and cats is ___________. a. 6–12 psig, b. 20.4–34 kPa, c. more than for rats and mice, d. none of the above

10. What flow rate and pressure of oil-free air is used to dry the interior of hoses? a. 5 scfm at 30 psig b. 10 scfm at 30 psig c. 5 scfm at 60 psig d. 10 scfm at 60 psig

11. What type of piping material should be used on systems that require frequent sterilization? a. cast iron b. copper c. galvanized d. stainless steel 12. The water consumption of small animals in cages is ___________. a. based on a flushing system to maintain fresh water in the piping at all times b. established by experience c. very low d. none of the above

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Animal-care Facility Piping Systems (PSD 136)

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Plumbing Systems & Design 11


PSD 143

Recirculating Domestic Hot Water Systems

Continuing Education from Plumbing Systems & Design Haig Demergian, PE, CPD

DECEMBER 2007

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Recirculating Domestic Hot Water Systems


INTRODUCTION It has been determined through field studies that the correct sizing and operation of water heaters depend on the appropriateness of the hot water maintenance system. If the hot water maintenance system is inadequate, the water heater sizing criteria are wrong and the temperature of the hot water distributed to the users of the plumbing fixtures is below acceptable standards. Additionally, a poorly designed hot water maintenance system wastes large amounts of energy and potable water and creates time delays for those using the plumbing fixtures. This chapter addresses the criteria for establishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water recirculation system and plumbing fixtures. It also discusses the temperature drop across a hot water supply system, types of hot water recirculation system, and pump selection criteria, and gives extensive information on the insulation of hot water supply and return piping.

Background

culated, dead-end branches to periodically used plumbing fixtures. The new allowable distances for uncirculated, dead-end branches represent a trade-off between the energy utilized by the hot water maintenance system and the cost of the insulation, on the one hand, and the cost of energy to heat the excess cold water makeup, the cost of wasted potable water, and extra sewer surcharges, on the other hand. Furthermore, engineers should be aware that various codes now limit the length between the hot water maintenance system and plumbing fixtures. They also should be aware of the potential for liability if an owner questions the adequacy of their hot water system design. What are reasonable delays in obtaining hot water at a fixture? For anything beside very infrequently used fixtures (such as those in industrial facilities or certain fixtures in office buildings), a delay of 0 to 10 sec is normally considered acceptable for most residential occupancies and public fixtures in office buildings. A delay of 11 to 30 sec is marginal but possibly acceptable, and a time delay longer than 31 sec is normally considered unacceptable and a significant waste of water and energy. Therefore, when designing hot water systems, it is prudent for the designer to provide some means of getting hot water to the fixtures within these acceptable time limits. Normally this means that there should be a maximum distance of approximately 25 ft (7.6 m) between the hot water maintenance system and each of the plumbing fixtures requiring hot water, the distance depending on the water flow rate of the plumbing fixture at the end of the line and the size of the line. (See Tables 1, 2, and 3.) The plumbing designer may want to stay under this length limitation because the actual installation in the field may differ slightly from the engineer’s design, and additional delays may be caused

In the past, the plumbing engineering community considered the prompt delivery of hot water to fixtures either a requirement for a project or a matter of no concern. The plumbing engineer’s decision was based primarily on the type of facility under consideration and the developed length from the water heater to the farthest fixture. Previous reference material and professional common practices have indicated that, when the distance from the water heater to the farthest fixture exceeds 100 ft (30.48 m) water should be circulated. However, this recommendation is subjective, and, unfortunately, some engineers and contractors use the 100-ft (30.48-m) criterion as the maximum length for all uncirculated, uninsulated, dead-end hot water branches to fixtures in order to cut the cost of hot water distribution piping. These long, uninsulated, dead-end Table 1 Water Contents and Weight of Tube or Piping per Linear Foot branches to fixtures create considerable problems, such as a Nominal Copper Pipe Copper Pipe Steel Pipe lack of hot water at fixtures, inadequately sized water heater Diameter Type L Type M Schedule 40 assemblies, and thermal temperature escalation in showers. Water Wgt. Water Wgt. Water Wgt. (in.)a (gal/ft) (lb/ft) (gal/ft) (lb/ft) (gal/ft) (lb/ft) The 100-ft (30.48-m) length criterion was developed in 1973 ½ 0.012 0.285 0.013 0.204 0.016 0.860 after the Middle East oil embargo, when energy costs were the paramount concern and water conservation was given little ¾ 0.025 0.445 0.027 0.328 0.028 1.140 consideration. Since the circulation of hot water causes a loss 1 0.043 0.655 0.045 0.465 0.045 1.680 of energy due to radiation and convection in the circulated 1¼ 0.065 0.884 0.068 0.682 0.077 2.280 system and such energy losses have to be continually replaced 1½ 0.093 1.14 0.100 0.940 0.106 2.720 by water heaters, the engineering community compromised a Pipe sizes are indicated for mild steel pipe sizing. between energy loss and construction costs and developed Table 1(M) Water Contents and Weight of Tube or Piping per Meter the 100-ft (30.48-m) maximum length criterion.

Nominal Diameter

Length and Time Criteria Recently, due to concern about not only energy conservation but also the extreme water shortages in parts of the country, the 100-ft (30.48-m) length criteria has changed. Water wastage caused by the long delay in obtaining hot water at fixtures has become as critical an issue as the energy losses caused by hot water temperature maintenance systems. To reduce the wasting of cooled hot water significantly, the engineering community has reevaluated the permissible distances for uncir-

(mm)a DN15 DN20 DN25 DN32 DN40 a

Copper Pipe Type L Water Wgt. (L) (kg) 0.045 0.129 0.095 0.202 0.163 0.297 0.246 0.401 0.352 0.517

Copper Pipe Type M Water Wgt. (L) (kg) 0.049 0.204 0.102 0.328 0.170 0.465 0.257 0.682 0.379 0.940

Steel Pipe Schedule 40 Water Wgt. (L) (kg) 0.061 0.390 0.106 0.517 0.170 0.762 0.291 1.034 0.401 1.233

CPVC Pipe Schedule 40 Water Wgt. (gal/ft) (lb/ft) 0.016 0.210 0.028 0.290 0.045 0.420 0.078 0.590 0.106 0.710

CPVC Pipe Schedule 40 Water Wgt. (L) (kg) 0.061 0.099 0.106 0.132 0.170 0.191 0.295 0.268 0.401 0.322

Pipe sizes are indicated for mild steel pipe sizing.

Reprinted from Domestic Water Heating Design Manual, Second Edition, Chapter 14: “Recirculating Domestic Hot Water Systems.” © American Society of Plumbing Engineers , 2003.

2 Plumbing Systems & Design

DECEMBER 2007

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Results of Delays in Delivering Hot Water to Fixtures

Table 2 Approximate Fixture and Appliance Water Flow Rates Maximum Flow Ratesa Fittings GPM L/Sec Lavatory faucet 2.0 1.3 Public non-metering 0.5 0.03 Public metering 0.25 gal/cycle 0.946 L/cycle Sink faucet 2.5 0.16 Shower head 2.5 0.16 Bathtub faucets Single-handle 2.4 minimum 0.15 minimum Two-handle 4.0 minimum 0.25 minimum Service sink faucet 4.0 minimum 0.25 minimum Laundry tray faucet 4.0 minimum 0.25 minimum Residential dishwasher 1.87 aver 0.12 aver Residential washing machine 7.5 aver 0.47 aver


As mentioned previously, when there is a long delay in obtaining hot water at the fixture, there is significant wastage of potable water as the cooled hot water supply is simply discharged down the drain unused. Furthermore, plumbing engineers concerned about total system costs should realize that the cost of this wasted, previously heated water must include: the original cost for obtaining potable water, the cost of previously heating the water, the final cost of the waste treatment of this excess potable water, which results in larger sewer surcharges (source of supply to end disposal point), and the cost of heating the new cold water to bring it up to the required temperature. Furthermore, if there is a long delay in obtaining hot water at the fixtures, the faucets are turned on for long periods of time to bring the hot water supply at the fixture up to the desired temperature. This can cause the water heating system to run out of a Unless otherwise noted. hot water and make the heater sizing inadequate, because the heater is unable to heat all the extra cold water brought Table 3 Approximate Time Required to Get Hot Water to a Fixture into the system through the wastage of the water discharged Delivery Time (sec) down the drain. In addition, this extra cold water entering Fixture Flow Rate (gpm) 0.5 1.5 2.5 4.0 the hot water system reduces the hot water supply temperature. This exacerbates the problem of insufficient hot water Piping Length (ft) 10 25 10 25 10 25 10 25 because to get a proper blended temperature more lower Copper ½ in. 25 63a 8 21 5 13 3 8 temperature hot water will be used to achieve the final mixed Pipe ¾ in. 48a 119a 16 40a 10 24 6 15 water temperature. (See Chapter 1, Table 1.1.) Additionally, Steel Pipe ½ in. 63a 157a 21 52a 13 31a 8 20 this accelerates the downward spiral of the temperature of Sched. 40 ¾ in. 91a 228a 30 76a 18 46a 11 28 the hot water system. CPVC Pipe ½ in. 64a 159a 21 53a 13 32a 8 20 Another problem resulting from long delays in getting hot Sched. 40 ¾ in. 95a 238a 32 79a 19 48a 12 30 water to the fixtures is that the fixtures operate for longer than Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based expected periods of time. Therefore, the actual hot water on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on demand is greater than the demand normally designed for. water temperature of 140°F and an air temperture of 70°F. Therefore, when sizing the water heater and the hot water a Delays longer than 30 sec are not acceptable. piping distribution system, the designer should be aware that the lack of a proper hot water maintenance system can Table 3(M) Approximate Time Required to Get Hot Water to a Fixture seriously impact the required heater size. Delivery Time (sec)

Fixture Flow Rate (L/sec) Piping Length (m) Copper Pipe Steel Pipe Sched. 40 CPVC Pipe Sched. 40

0.03 DN15 DN22 DN15 DN20 DN15 DN20

3.1 25 48a 63a 91a 64a 95a

0.10 7.6 63a 119a 157a 228a 159a 238a

3.1 8 16 21 30 21 32

0.16 7.6 21 40a 52a 76a 53a 79a

3.1 5 10 13 18 13 19

Methods of Delivering Reasonably Prompt Hot Water Supply

0.25 7.6 13 24 31a 46a 32a 48a

3.1 3 6 8 11 8 12

7.6 8 15 20 28 20 30

Note: Table based on various fixture flow rates, piping materials, and dead-end branch lengths. Calculations are based on the amount of heat required to heat the piping, the water in the piping, and the heat loss from the piping. Based on water temperature of 60°C and an air temperture of 21.1°C. a Delays longer than 30 sec are not acceptable.

by either the routing of the pipe or other problems. Furthermore, with the low fixture discharge rates now mandated by national and local laws, it takes considerably longer to obtain hot water from non-temperature maintained hot water lines than it did in the past, when fixtures had greater flow rates. For example, a public lavatory with a 0.50 or 0.25 gpm (0.03 or 0.02 L/sec) maximum discharge rate would take an excessive amount of time to obtain hot water from 100 ft (30.48 m) of uncirculated, uninsulated hot water piping. (See Table 3.) This table gives conservative approximations of the amount of time it takes to obtain hot water at a fixture. The times are based on the size of the line, the fixture flow rate, and the times required to replace the cooled off hot water, to heat the pipe, and to offset the convection energy lost by the insulated hot water line.

Hot water maintenance systems are as varied as the imaginations of the plumbing engineers who create them. They can be grouped into three basic categories, though any actual installation may be a combination of more than one of these types of system. The three basic categories are 1. Circulation systems. 2. Self-regulating heat trace systems. 3. Point-of-use water heaters (include booster water heaters).

Circulation Systems for Commercial, Industrial, and Large Residential Projects

A circulation system is a system of hot water supply pipes and hot water return pipes with appropriate shutoff valves, balancing valves, circulating pumps, and a method of controlling the circulating pump. The diagrams for six basic circulating systems are shown in Figures 1 through 6.

Self-Regulating Heat Trace Over approximately the last 20 years, self-regulating heat trace has come into its own because of the problems of balancing circulated hot water systems and energy loss in the return piping. For further discussion of this topic, see Chapter 15.

DECEMBER 2007


CONTINUING EDUCATION: Recirculating Domestic Hot Water Systems Point-of-Use Heaters

Fixture 1 Upfeed Hot Water System with Heater at Bottom of System.


This concept is applicable when there is a single fixture or group of fixtures that is located far from the temperature maintenance system. In such a situation, a small, instantaneous, pointof-use water heater—an electric water heater, a gas water heater, or a small under-fixture storage type water heater of the magnitude of 6 gal (22.71 L)—can be provided. (See Figure 7.) The point-of-use heater will be very cost-effective because it will save the cost of running hot water piping to a fixture that is a long distance away from the temperature maintenance system. The plumbing engineer must remember, however, that when a water heater is installed there are various code and installation requirements that must be complied with, such as those pertaining to T & P relief valve discharge. Instantaneous electric heaters used in pointof-use applications can require a considerable amount of power, and may require 240 or 480 V service.

Potential Problems in Circulated Hot Water Maintenance Systems

* See text for requirements for strainers.

Figure 2 Downfeed Hot Water System with Heater at Top of System.

The following are some of the potential problems with circulated hot water maintenance systems that must be addressed by the plumbing designer.

Water Velocities in Hot Water Piping Systems For copper piping systems, it is very important that the circulated hot water supply piping and especially the hot water return piping be sized so that the water is moving at a controlled velocity. High velocities in these systems can cause pinhole leaks in the copper piping in as short a period as six months or less.

Balancing Systems It is extremely important that a circulated hot water system be balanced for its specified flows, including all the various individual loops within the circulated system. Balancing is required even though an insulated circulated line usually requires very little flow to maintain satisfactory system temperatures. If the individual hot water circulated loops are not properly balanced, the circulated water will tend to shortcircuit through the closest loops, creating high velocities in that piping system. Furthermore, the short-circuiting of the circulated hot water will result in complaints about the long delays in getting hot water at the remotest loops. If the hot water piping is copper, high velocities can create velocity erosion which will destroy the piping system. Because of the problems inherent in manually balancing hot water circulation systems, many professionals incorporate factory preset flow control devices in their hot water systems. While the initial cost of such a device is higher than the cost of a manual balancing valve, a


DECEMBER 2007


Figure 3 Upfeed Hot Water System with Heater at Bottom of System.


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Figure 4 Downfeed Hot Water System with Heater at Top of System.

preset device may be less expensive when the balancing the entire hot water system is included. When using a preset flow control device, however, the plumbing designer has to be far more accurate in selecting the control device’s capacity as there is no possibility of field adjustment. Therefore, if more or less hot water return flow is needed during the field installation, a new flow control device must be installed and the old one must be removed and discarded.

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com field labor cost for

Isolating Portions of Hot Water Systems


Figure 5 Combination Upfeed and Downfeed Hot Water System with Heater at Bottom of System.

It is extremely important in circulated systems that shutoff valves be provided to isolate an entire circulated loop. This is done so that if individual fixtures need modification, their piping loop can be isolated from the system so the entire hot water system does not have to be shut off and drained. The location of these shutoff valves should be given considerable thought. The shutoff valves should be accessible at all times, so they should not be located in such places as the ceilings of locked offices or condominiums.

Maintaining the Balance of Hot Water Systems

Note: This piping system increases the developed length of the HW system over the upfeed systems shown in Figures 1 and 3. * See text for requirements for strainers.

Figure 6 Combination Downfeed and Upfeed Hot Water System with Heater at Top of System.

To ensure that a balanced hot water system remains balanced after the shutoff valves have been utilized, the hot water return system must be provided with a separate balancing valve in addition to the shutoff valve or, if the balancing valve is also used as the shutoff valve, the balancing valve must have a memory stop. (See the discussion of “balancing valves with memory stops” below.) With a memory stop on the valve, plumbers can return a system to its balanced position after working on it rather than have the whole piping system remain unbalanced, which would result in serious problems.

Providing Check Valves at the Ends of Hot Water Loops The designer should provide a check valve on each hot water return line where it joins other hot water return lines. This is done to ensure that a plumbing fixture does not draw hot return water instead of hot supply water, which could unbalance the hot water system and cause delays in obtaining hot water at some fixtures.

A Delay in Obtaining Hot Water at Dead-End Lines Keep the delay in obtaining hot water at fixtures to within the time (and branch length) parameters given previously to avoid unhappy users of the hot water system and to prevent lawsuits.

Flow Balancing Devices Note: This piping system increases the developed length of the HW system over the downfeed systems shown in Figures 2 and 4. * See text for requirements for strainers.

The following are the more common types of balancing device. DECEMBER 2007


CONTINUING EDUCATION: Recirculating Domestic Hot Water Systems Fixed Orifices and Venturis

Figure 7 Instantaneous Point-of-Use Water Heater Piping Diagram.


Source: Courtesy of Chronomite Laboratories, Inc.

These can be obtained for specific flow rates and simply inserted into the hot water return piping system. (See Figure 8.) However, extreme care should be taken to locate these devices so they can be removed and cleaned out, as they may become clogged with the debris in the water. It is recommended, therefore, that a strainer with a blowdown valve be placed ahead of each of these devices. Additionally, a strainer with a fine mesh screen can be installed on the main water line coming into the building to help prevent debris buildup in the individual strainers. Also, a shutoff valve should be installed before and after these devices so that an entire loop does not have to be drained in order to service a strainer or balancing device.

Factory Preset Automatic Flow Control Valves The same admonition about strainers and valves given for “fixed orifices and venturis” above applies to the installation and location of these devices. (See Figure 9.)

Flow Regulating Valves These valves can be used to determine the flow rate by reading the pressure drop across the valve. They are available from various manufacturers. (See Figure 10.)

Balancing Valves with Memory Stops These valves can be adjusted to the proper setting by installing insertable pressure measuring devices (Pete’s Plugs, etc.) in the piping system, which indicate the flow rate in the pipe line. (See Figure 11.)

Sizing Hot Water Return Piping Systems and Recirculating Pumps The method for selecting the proper size of the hot water return piping system and the recirculating pump is fairly easy, but it does require engineering judgment. First, the plumbing engineer has to design the hot water supply and hot water return piping systems, keeping in mind the parameters for total developed length,1 prompt delivery of hot water to fixtures, and velocities in pipe lines. The plumbing engineer has to make assumptions about the sizes of the hot water return piping. After the hot water supply and hot water return systems are designed, the designer should make a piping diagram of the hot water supply system and the assumed return system showing piping sizing and approximate lengths. From this piping diagram the hourly heat loss occurring in the circulated portion of the hot water supply and return systems can be determined. (See Table 4 for minimum required insulation thickness and Table 5 for approximate piping heat loss.) Next determine the heat loss in the hot water storage tank if one is provided. (See Table 6 for approximate tank heat loss.) Calculate the total hot water system energy loss (tank heat loss plus piping heat loss) in British thermal units per hour (watts). This total hot water system energy loss is represented by q in Equation 1 below. Note: Heat losses from storage type water heater tanks are not normally included in the hot water piping system heat loss because the water heater capacity takes care of this loss, whereas pumped hot water has to replace the piping convection losses in the piping system. (1) q = 60rwc∆T [q = 3600rwc∆T]


DECEMBER 2007

where

60 = min/h 3600 = sec/h q = piping heat loss, Btu/h (kJ/h) r = flow rate, gpm (L/sec) w = weight of heated water, lb/gal (kg/L) c = specific heat of water, Btu/lb/°F (kJ/kg/K) ∆T = change in heated water temperature (temperature of leaving water minus temperature of incoming water, represented in this manual as Th – Tc, °F [K])

Therefore

q = c (gpm × 8.33 lb/gal)(60 min/h)(°F temperature drop) = 1(gpm) × 500 × °F temperature drop [q = c (L/sec • 1kg/L)(3600 sec/h)(K temperature drop) = 1(L/sec) • 15 077 kJ/L/sec/K • K temperature drop] system heat loss (Btu/h) 500 × °F temperature drop system heat loss (kJ/h) L/sec ≈ 15 077 • K temperature drop In sizing hot water circulating systems, the designer should note that the greater the temperature drop across the system, the less water is required to be pumped through the system and, therefore, the greater the savings on pumping costs. However, if the domestic hot water supply starts out at 140°F (60°C) with, say, a 20°F (6.7°C) temperature drop across the supply system, the fixtures near the end of the circulating hot water supply loop could be provided with a hot water supply of only 120°F (49°C). In addition, if the hot water supply delivery temperature is 120°F (49°C) instead of 140°F (60°C), the plumbing fixtures will use greater volumes of hot water to get the desired blended water temperature (see Chapter 1, Table 1.1). Therefore, the recommended hot water system temperature drop should be of the magnitude of 5°F (3°C). This means that if the hot water supply starts out from the water heater at a temperature between 135 and 140°F (58 and 60°C), the lowest hot water supply temperature provided by the hot water supply system could (2) gpm ≈

[

]

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Figure 9 Preset Self-Limiting Flow Control Cartridge.

Figure 8 Fixed Orifices and Venturi Flow Meters.

Source: Courtesy of Gerand Engineering Co.

Source: Courtesy of Griswold Controls.


be between 130 and 135°F (54 and 58°C). With multiple temperature distribution systems, it is recommended that the recirculation system for each temperature distribution system be extended back to the water heating system separately and have its own pump. Using Equation 2, we determine that, if there is a 5°F (3°C) temperature drop across the hot water system, the number to divide into the hot water circulating system heat loss (q) to obtain the minimum required hot water return circulation rate in gpm (L/sec) is 2500 (500 × 5°F), (45 213 [15 071 • 3°C]). For a 10°F (6°C) temperature drop that number is 5000 (from Equation 2, 500 × 10°F = 5000) (90 426 [from Equation 2, 15 071 • 6°C = 90 426]). However, this 10°F (6°C) temperature drop may produce hot water supply temperatures that are lower than desired. After Equation 2 is used to establish the required hot water return flow rate, in gpm (L/sec), the plumbing designer can size the hot water return piping system based on piping flow rate velocities and the available pump heads. It is quite common that a plumbing designer will make wrong initial assumptions about the sizes

of the hot water return lines to establish the initial heat loss figure (q). If that is the case, the plumbing engineer will have to correct the hot water return pipe sizes, redo the calculations using the new data based on the correct pipe sizing, and verify that all the rest of the calculations are now correct.

EXAMPLE 1 — CALCULATION TO DETERMINE REQUIRED CIRCULATION RATE 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1 ¼ in. (DN32) pipe. From Table 5, determine the heat loss per linear foot (meter). To find the total heat loss, multiply length times heat loss per foot (meter):

800 ft × 13 Btu/h/ft = 10,400 Btu/h supply piping losses (244 m • 12.5 W = 3050 W supply piping losses) 2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) piping and 100 ft (30.5 m) of average ¾ in. (DN20) pipe. From Table 5 determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 800 Btu/h piping loss (30.5 m • 7.7 W/m = 235 W piping loss) 100 ft × 10 Btu/h/ft = 1000 Btu/h piping loss 1800 Btu/h piping loss

(30.5 m

•

9.6 W/m =

293 W piping loss 528 W piping loss

)

3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage DECEMBER 2007


CONTINUING EDUCATION: Recirculating Domestic Hot Water Systems Figure 10 Adjustable Orifice Flow Control Valve.

Source: ITT Industries. Used with permission.


tank. From Table 6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the hot water system’s total heat losses by totaling the various losses: A. Hot water supply piping losses 10,400 Btu/h B. Hot water return piping losses 1,800 Btu/h C. Hot water storage tank losses 759 Btu/h Total system heat losses 12,959 Btu/h Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply piping losses 3050 W B. Hot water return piping losses 527 W C. Hot water storage tank losses 222 W Total system heat losses 3799 W Total system piping heat losses (A + B) = 3577 W] From Equation 2, using a system piping loss of 12,200 Btu/h (3577 W) and a 5°F (3°C) temperature drop,

Source: Courtesy of Milwaukee Valve Co.

Figure 11 Adjustable Balancing Valve with Memory Stop.

12,200 Btu/h = 4.88 gpm (say 5 gpm) 5°F temperature difference × 500 required hot water return circulation rate 3577 W = 0.29 (say 0.3) L/sec 3 3°C temp. difference • 4188.32 kJ/m required hot water return circulation

Recalculation of Hot Water System Losses 1. Assume that the hot water supply piping system has 800 ft (244 m) of average size 1¼ in. (DN32) pipe. From Table 5 determine the heat loss per linear foot (meter): 800 ft × 13 Btu/h/ft = 10,400 Btu/h piping loss (244 m • 12.5 W/m = 3050 W piping loss) 2. Assume that the hot water return piping system for the system in no. 1 above has 100 ft (30.5 m) of average ½ in. (DN15) pipe, 25 ft (7.6 m) of average ¾ in. (DN22) pipe, and


DECEMBER 2007

75 ft (22.9 m) of average 1 in. (DN28) pipe. From Table 5, determine the heat loss per linear foot (meter): 100 ft × 8 Btu/h/ft = 25 ft × 10 Btu/h/ft = 75 ft × 10 Btu/h/ft =

800 Btu/h piping loss 250 Btu/h piping loss 750 Btu/h piping loss 1800 Btu/h piping loss

[30.5 m • 7.7 W/m = 235 W piping loss PSDMAGAZINE.ORG

Table 4 Minimum Pipe Insulation Thickness Simpo PDF Merge and Split Unregistered Version Required Insulation Thickness for Piping (in.) Runouts 2a 8 in. or in. or Less 1 in. or Less 1¼–2 in. 2½–4 in. 5 & 6 in. Larger ½ 1 1 1½ 1½ 1½ Note: Data based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 3 ft from the storage tank of uncirculated systems. a Uncirculated pipe branches to individual fixtures (not exceeding 12 ft in length). For lengths longer than 12 ft, use required insulation thickness shown in table.

Table 4(M) Minimum Pipe Insulation Thickness Required Insulation Thickness for Piping (mm) Runouts DN32 aor DN25 or DN32– DN65– DN125 & Less Less DN50 DN100 DN150 13 25 25 40 40

DN200 or Larger 40

Note: D ata based on fiberglass insulation with all-service jacket. Data will change depending on actual type of insulation used. Data apply to recirculating sections of hot water systems and the first 0.9 m from the storage tank of uncirculated systems. a Uncirculated pipe branches to individual fixtures (not exceeding 3.7 m in length). For lengths longer than 305 mm, use required insulation thickness shown in table.

Table 5 Approximate Insulated Piping Heat Loss and Surface Temperature Surface Nominal Pipe Insulation Heat Loss Temperature Size (in.) Thickness (in.) (Btu/h/ linear ft) (°F) ½ 1 8 68 ¾ 1 10 69 1 1 10 69 1¼ 1 13 70 1½ 1 13 69 2 or less ½a 24 or less 74 2 1 16 70 2½ 1½ 12 67 3 1½ 16 68 4 1½ 19 69 6 1½ 27 69 8 1½ 32 69 10 1½ 38 69 Note: Figures based on average ambient temperature of 65°F and annual average wind speed of 7.5 mph. a Uncirculating hot water runout branches only.

Table 5(M) Approximate Insulated Piping Heat Loss and Surface Temperature Surface Nominal Pipe Insulation Heat Loss Temperature Size (mm) Thickness (mm) (W/m) (°C) DN15 25 7.7 20 DN20 25 9.6 21 DN25 25 9.6 21 DN32 25 12.5 21 DN40 25 12.5 21 DN50 or less 13a 23.1 or less 23 DN50 25 15.4 21 DN65 38 11.5 19 DN80 38 15.4 20 DN100 38 18.3 21 DN150 38 26.0 21 DN200 38 30.8 21 DN250 38 36.5 21 Note: Figures based on average ambient temperature of 18°C and annual average wind speed of 12 km/h. a Uncirculating hot water runout branches only.

Table 6 Heat Loss from Various Size Tanks with

- http://www.simpopdf.com Various Insulation Thicknesses

Insulation Approx. Energy Loss Thickness Tank Size from Tank at Hot Water a (in.) (gal) Temperature 140°F (Btu/h) 1 50 468 1 100 736 2 250 759 3 500 759 3 1000 1273 Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. a For unfired tanks, federal standards limit the loss to no more than 6.5 Btu/h/ft2 of tank surface.

Table 6(M) Heat Loss from Various Size Tanks with Various Insulation Thicknesses Insulation Approx. Energy Loss Thickness Tank Size from Tank at Hot Watera (mm) (L) Temperature 60°C (W) 25.4 200 137 25.4 400 216 50.8 1000 222 76.2 2000 222 76.2 4000 373 Source: From Sheet Metal and Air Conditioning Contractors National Association (SMACNA) Table 2 data. a For unfired tanks, federal standards limit the loss to no more than 1.9 W/m2 of tank surface.

7.6 m • 9.6 W/m = 73 W piping loss 22.9 m • 9.6 W/m = 220 W piping loss 528 W piping loss] 3. Determine the hot water storage tank heat loss. Assume the system in no. 1 above has a 200-gal (757-L) hot water storage tank. From Table 6 determine the heat loss of the storage tank @ 759 Btu/h (222 W). 4. Determine the system’s total heat losses: A. Hot water supply losses 10,400 Btu/h B. Hot water return losses 1,800 Btu/h C. Hot water storage tank losses 759 Btu/h Total system heat losses 12,959 Btu/h Total system piping heat losses (A + B) = 12,200 Btu/h [A. Hot water supply losses B. Hot water return losses C. Hot water storage tank losses Total system heat losses Total system piping heat losses (A + B) =

3050 W 528 W 222 W 3800 W 3578 W]

Note: The recalculation determined that the hot water system heat losses remained unchanged and that 4.88 (say 5) gpm (0.29 [say 0.3] L/sec) is the flow rate that is required to maintain the 5°F (3°C) temperature drop across the hot water supply system. It should be stated that engineers use numerous rules of thumb to size hot water return systems. These rules of thumb are all based on assumptions, however, and are not recommended. It is recommended that the engineer perform the calculations for each project to establish the required flow rates because, with all the various capacities of the pumps available today, exact sizing is possible, and any extra circulated flow caused by the plumbing engineer using a rule of thumb equates to higher energy costs, to the detriment of the client.

Establishing the Head Capacity of the Hot Water Circulating Pump DECEMBER 2007


CONTINUING EDUCATION: Recirculating Domestic Hot Water Systems The hot water return circulating pump is selected based on the It can be used very successfully for residential and commercial Simpo PDFreturn Merge and(inSplit Unregistered - http://www.simpopdf.com required hot water flow rate gpm [L/sec]), calculatedVersion using applications. Equation 2, and the system’s pump head. The pump head is nor- 2. A thermostatic aquastat is a device that is inserted into the mally determined by the friction losses through only the hot water hot water return line. When the water in the hot water return return piping loops and any losses through balancing valves. The hot system reaches the distribution temperature, it shuts off the water return piping friction losses usually do not include the friction circulating pump until the hot water return system temperalosses that occur in the hot water supply piping. The reason for this is ture drops by approximately 10°F [5.5°C]. With this method, that the hot water return circulation flow is needed only to keep the when there is a large consumption of hot water by the plumbhot water supply system up to the desired temperature when there ing fixtures, the circulating pump does not operate. is no flow in the hot water supply piping. When people use the hot 3. A time clock is used to turn the pump on during specific hours water at the fixtures, there is usually sufficient flow in the hot water of operation when people are using the fixtures. The pump supply piping to keep the system hot water supply piping up to the would not operate, for example, at night in an office building desired temperature without help from the flow in the hot water when nobody is using the fixtures. return piping. 4. Often an aquastat and a time clock are used in conjunction The only exception to the rule of ignoring the friction losses in the so that during the hours a building is not operating the time hot water supply piping is a situation where a hot water return pipe clock shuts off the circulating pump, and during the hours the is connected to a relatively small hot water supply line. “Relatively building is in use the aquastat shuts off the pump when the small” here means any hot water supply line that is less than one system is up to the desired temperature. pipe size larger than the hot water return line. The problems created by this condition are that the hot water supply line will add Air Elimination additional friction to the head of the hot water circulating pump, In any hot water return circulation system it is very important that and the hot water circulating pump flow rate can deprive the last there be a means of eliminating any entrapped air from the hot plumbing fixture on this hot water supply line from obtaining its water return piping. Air elimination is not required in the hot water required flow. It is recommended, therefore, that in such a situation supply piping because the discharge of water from the fixtures will the hot water supply line supplying each hot water return piping eliminate any entrapped air. If air is not eliminated from the hot connection point be increased to prevent these potential problems, water return lines, however, it can prevent the proper circulation i.e., use ¾ in. (DN22) hot water supply piping and ½ in. (DN15) hot of the hot water system. It is imperative that a means of air elimiwater return piping, or 1 in. (DN28) hot water supply piping and ¾ nation be provided at all high points of a hot water return system. The plumbing engineer must always give consideration to precisely in. (DN22) hot water return piping, etc. When selecting the hot water circulating pump’s head, the where the air elimination devices are to be located and drained. For designer should be sure to calculate only the restrictions encoun- example, they should not be located in the unheated attics of buildtered by the circulating pump. A domestic hot water system is nor- ings in cold climates. If the plumbing engineer does not consider mally considered an open system (i.e., open to the atmosphere). the location of these devices and where they will drain, the result When the hot water circulating pump is operating, however, it is may be unsightly piping in a building or extra construction costs. assumed that the piping is a closed system. Therefore, the designer Insulation should not include static heads where none exists. For example, in The use of insulation is very cost-effective. It means paying one time Figure 1, the hot water circulating pump has to overcome only the to save the later cost of significant energy lost by the hot water supply friction in the hot water return piping not the loss of the static head and return piping system. Also, insulation decreases the stresses pumping the water up to the fixtures because in a closed system on the piping due to thermal expansion and contraction caused the static head loss is offset by the static head gain in the hot water by changes in water temperature. Furthermore, the proper use of return piping. insulation eliminates the possibility of someone getting burned by a hot, uninsulated water line. See Table 5 for the surface temperaHot Water Circulating Pumps Most hot water circulating pumps are of the centrifugal type and are tures of insulated lines (versus 140°F [60°C] for bare piping). It is recommended that all hot water supply and return piping be available as either in-line units for small systems or base-mounted insulated. This recommendation exceeds some code requirements. units for large systems. Because of the corrosiveness of hot water See Table 4 for the minimum required insulation thicknesses for all systems, the pumps should be bronze, bronze fitted, or stainless systems. steel. Conventional, iron bodied pumps, which are not bronze If the insulated piping is installed in a location where it is subfitted, are not recommended. jected to rain or other water, the insulation must be sealed with a Control for Hot Water Circulating Pumps watertight covering that will maintain its tightness over time. Wet There are three major methods commonly used for controlling hot insulation not only does not insulate, it also releases considerable water circulating pumps: manual, thermostatic (aquastat), and heat energy from the hot water piping, thus wasting energy. Furtime clock control. Sometimes more than one of these methods are thermore, the insulation on any outdoor lines that is not sealed used on a system. watertight can be plagued by birds or rodents, etc., pecking at the 1. A manual control runs the hot water circulating pump contin- insulation to use it for their nests. In time, the entire hot water uously when the power is turned on. A manual control should supply and/or return piping will have no insulation. Such bare hot be used only when hot water is needed all the time, 24 h a day, water supply and/or return piping will waste considerable energy or during all the periods of a building’s operation. Otherwise, and can seriously affect the operation of the hot water system and it is not a cost-effective means of controlling the circulating water heaters. pump because it will waste energy. The minimum required insulation thicknesses given in Table 4 are based on insulation having thermal resistivity (R) in the range of Note: The method for applying the “on demand” concept for 4.0 to 4.6 ft2 × h × (°F/Btu) × in. (0.028 to 0.032 m2 • [°C/W] • mm) on a controlling the hot water circulating pump is a manual control. flat surface at a mean temperature of 75°F (24°C). Minimum insula-


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tion thickness shall be increased for materials having R values less 14. American Society of Plumbing Engineers. 2000. Energy conPDF Merge (0.028 and Split Unregistered Version - http://www.simpopdf.com • mm) or may be thanSimpo 4.0 ft2 × h × (°F/Btu) × in. m2 • [°C/W] servation in plumbing systems. Chapter 7 in ASPE Data Book, 2 reduced for materials having R values greater than 4.6 ft × h × (°F/ Volume 1. Btu) × in. (0.032 m2 • [°C/W] • mm). 15. American Water Works Association. 1985. Internal corrosion 1. For materials with thermal resistivity greater than 4.6 of water distribution systems. Research Foundation cooperaft2 × h × (°F/Btu) × in. (0.032 m2 • [°C/W] • mm), the minimum tive research report. insulation thickness may be reduced as follows: 16. Cohen, Arthur. Copper Development Association. 1978. Copper for hot and cold potable water systems. Heating/ 4.6 × Table 4 thickness = New minimum thickness Piping/Air Conditioning Magazine. May. Actual R 17. Cohen, Arthur. Copper Development Association. 1993. His0.032 • Table 4 thickness = New minimum thickness Actual R torical perspective of corrosion by potable waters in building systems. Paper no. 509 presented at the National Association 2. For materials with thermal resistivity less than 4.0 ft2 × h × (°F/ of Corrosion Engineers Annual Conference. Btu) × in. (0.028 m2 • [°C/W] • mm), the minimum insulation 18. Copper Development Association. 1993. Copper Tube Handthickness shall be increased as follows: book. 4.0 × Table 4 thickness = New minimum thickness 19. International Association of Plumbing and Mechanical OffiActual R cials. 1985. Uniform Plumbing Code Illustrated Training Manual. 0.028 • Table 4 thickness = New minimum thickness Actual R 20. Konen, Thomas P. 1984. An experimental study of competing systems for maintaining service water temperature in residenConclusion tial buildings. In ASPE 1984 Convention Proceedings. In conclusion, an inappropriate hot water recirculation system can 21. Konen, Thomas P. 1994. Impact of water conservation on have serious repercussions for the operation of the water heater interior plumbing. In Technical Proceedings of the 1994 ASPE and the sizing of the water heating system. In addition, it can cause Convention. the wastage of vast amounts of energy, water, and time. Therefore, 22. Saltzberg, Edward. 1988. The plumbing engineer as a forensic it is incumbent upon the plumbing designer to design a hot water engineer. In Technical Proceedings of the 1988 ASPE Convention. recirculation system so that it conserves natural resources and is in 23. Saltzberg, Edward. 1993. To combine or not to combine: An accordance with the recommendations given in this chapter. ✺ in–depth review of standard and combined hydronic heating systems and their various pitfalls. Paper presented at the Bibliography American Society of Plumbing Engineers Symposium, Octo1. American Society of Heating, Refrigerating, and Air Condiber 22–23. tioning Engineers. 1993. Pipe sizing. Chapter 33 in Fundamen24. Saltzberg, Edward. 1996. The effects of hot water circulation tals Handbook. systems on hot water heater sizing and piping systems. Tech2. American Society of Heating, Refrigerating, and Air Condinical presentation given at the American Society of Plumbing tioning Engineers. 1993. Thermal and water vapor transmisEngineers convention, November 3–6. sion data. Chapter 22 in Fundamentals Handbook. 25. Saltzberg, Edward. 1997. In press. New methods for analyzing 3. American Society of Heating, Refrigerating, and Air Condihot water systems. Plumbing Engineer Magazine. tioning Engineers. 1995. Service water heating. Chapter 45 in 26. Saltzberg, Edward. 1997. In press. Prompt delivery of hot Applications Handbook. water at fixtures. Plumbing Engineer Magazine. 4. American Society of Heating, Refrigerating, and Air Con27. Sealine, David A., Tod Windsor, Al Fehrm, and Greg Wilcox. ditioning Engineers. Energy conservation in new build1988. Mixing valves and hot water temperature. In Technical ing design. ASHRAE Standards, 90A–1980, 90B–1975, and Proceedings of the 1988 ASPE Convention. 90C–1977. 28. Sheet Metal and Air Conditioning Contractors National Asso5. American Society of Heating, Refrigerating, and Air Condiciation. 1982. Retrofit of Building Energy Systems and Processes. tioning Engineers. Energy efficient design of new low rise 29. Steele, Alfred. Engineered Plumbing Design. 2d ed. residential buildings. ASHRAE Standards, 90.2–1993. 30. Steele, Alfred. 1988. Temperature limits in service hot water 6. American Society of Heating, Refrigerating, and Air Condisystems. In Technical Proceedings of the 1988 ASPE Convention. tioning Engineers. New information on service water heating. 31. Wen-Yung, W. Chan, and Milton Meckler. 1983. Pumps and Technical Data Bulletin. Vol. 10, No. 2. pump systems. In American Society of Plumbing Engineers 7. American Society of Mechanical Engineers. Plumbing fixture Handbook. fittings. ASME A112.18.1M–1989. 8. American Society of Plumbing Engineers. 2000. Cold water systems. Chapter 5 in ASPE Data Book, Volume 2. 9. American Society of Plumbing Engineers. 1989. Piping systems. Chapter 10 in ASPE Data Book. 10. American Society of Plumbing Engineers. 1989. Position paper on hot water temperature limitations. 11. American Society of Plumbing Engineers. 1989. Service hot water systems. Chapter 4 in ASPE Data Book. 12. American Society of Plumbing Engineers. 1990. Insulation. Chapter 12 in ASPE Data Book. 13. American Society of Plumbing Engineers. 1990. Pumps. Chapter 11 in ASPE Data Book.

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Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Continuing Education from Plumbing Systems & Design Haig Demergian, PE, CPD

Now Online!

The technical article you must read to complete the exam is located at www.psdmagazine.org. Just click on “Plumbing Systems & Design Continuing Education Article and Exam” at the top of the page. The following exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward CPD renewal or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

About This Issue’s Article The December 2007 continuing education article is “Recirculating Domestic Hot Water Systems,” Chapter 14 of Domestic Water Heating Design Manual, Second Edition. This chapter addresses the criteria for establishing an acceptable time delay in delivering hot water to fixtures and the limitations of the length between a hot water recirculation system and plumbing fixtures. It also discusses the temperature drop across a hot water supply system, types of hot water recirculation system, and pump selection criteria, and gives extensive information on the insulation of hot water supply and return piping. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

PSD 143


CE Questions—“Recirculating Domestic Hot Water Systems” (PSD 143) 1. If the balancing valve is also used as the shutoff valve, the balancing valve must have a ___________. a. long stem b. flanged end c. memory stop d. none of the above 2. The water content of 1-inch Type L copper pipe is __________ gal/ft. a. 0.060 b. 0.052 c. 0.043 d. 0.039 3. Hot water recirculation systems with circulating pumps are installed in large buildings to __________. a. maintain constant hot water pressure at fixtures b. provide a reasonably prompt hot water supply to fixtures c. both of the above d. neither of the above 4. The approximate heat loss of a tank with 1-inch insulation holding 100 gallons of 140°F hot water is __________ Btu/h. a. 736, b. 137, c. 468, d. 1,273 5. The minimum recommended fiberglass pipe insulation thickness for a 2-inch diameter potable hot water pipe is __________. a. ¾ inch b. 1 inch c. 1½ inches d. 2 inches 6. The approximate heat loss of 1-inch copper pipe with 1-inch insulation (assuming 65°F ambient temperature) is __________ Btu/h per foot. a. 8, b. 10, c. 12, d. 14


DECEMBER 2007

7. The total estimated heat loss of 520 feet of 1½-inch copper pipe, with 1-inch fiberglass insulation, is __________ Btu/h. a. 6,000, b. 6,320, c. 6,760, d. 7,520

8. The approximate time to deliver hot water to a 1.5-gpm fixture 25 feet from the water heater, using ¾-inch copper supply pipe, is __________ seconds. a. 25, b. 30, c. 40, d. 50 9. The gpm of a hot water circulating pump for a system with a total calculated heat loss of 10,000 Btu/h and 5°F allowable temperature drop between hot water supply and return is __________. a. 3, b. 4, c. 7, d. 9 10. The heat required to raise 35 gpm from 50°F to 140°F is __________ Btu/h. a. 895,000 b. 1,270,000 c. 1,575,000 d. 1,625,000

11. Why it is necessary to provide a pressure relief valve on potable hot water systems? a. to relieve the water, which expands during the heating process b. to protect the water heater and piping from excessive pressure c. both of the above d. neither of the above

12. Automatic air vents for air elimination shall be installed on the high points of __________. a. hot water supply piping b. hot water return piping c. cold water supply piping d. none of the above

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Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Plumbing Systems & Design Continuing Education Application Form This form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who earn a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required). 1. Photocopy this form or download it from www.psdmagazine.org. 2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space. 3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form. 4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Ave., Suite 1007, Chicago, IL 60656) or fax (773-695-9007). Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_ _________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________

I am applying for the following continuing education credits: I certify that I have read the article indicated above.




Payment: ❏ Personal Check (payable to ASPE) $____________ ❏ Business or government check $ _________ ❏ DiscoverCard ❏ VISA ❏ MasterCard ❏ AMEX $____________ Signature Expiration date: Continuing education credit will be given for this examination through DECEMBER 31, 2008. Applications received after that date will not be processed.


If rebilling of a credit card charge is necessary, a $25 processing fee will be charged. ASPE is hereby authorized to charge my CE examination fee to my credit card Account Number Expiration date Signature

Recirculating Domestic Hot Water Systems (PSD 143) Questions appear on page 12. Circle the answer to each question. Q 1. A B C D Q 2. A B C D Q 3. A B C D Q 4. A B C D Q 5. A B C D Q 6. A B C D Q 7. A B C D Q 8. A B C D Q 9. A B C D Q 10. A B C D Q 11. A B C D Q 12. A B C D


Appraisal Questions

Recirculating Domestic Hot Water Systems (PSD 143) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No 6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________ 1. 2. 3. 4. 5.

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PSD 140

Flow in Water Piping


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Flow in Water Piping

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Hydraulics can be defined as the study of the principles and laws that govern the behavior of liquids at rest or in motion. Hydrostatics is the study of liquids at rest and hydrokinetics is the study of liquids in motion. Although this text deals exclusively with water, all the data developed can be applied to any liquid.

Physical Properties of Water The weight of water, or its density, varies with its temperature and purity. Water has its greatest specific weight (weight per cubic foot) at a temperature of 39.2°F. If this phenomenon did not occur, lakes would start freezing from the bottom up instead of from the top down. Table 1 tabulates densities of pure water at various temperatures. For the normal Table 1 Density of Pure Water at Various range of tempera- Temperatures tures met in plumbTemperature Density Temperature Density ing systems, the den°F lbm/ft3 °F lbm/ft3 32 62.416 100 61.988 sity of water is very 35 62.421 120 61.719 close to 62.4 lbm/ft3 39.2 62.424 140 61.386 and this value can be 40 62.423 160 61.006 used for all calcula50 62.408 180 60.586 tions without any 60 62.366 200 60.135 significant error. 70 62.300 212 59.843 Viscosity can be 80 62.217 defined as the internal friction, or internal resistance, to the relative motion of fluid particles. It can also be defined as the property by which fluids offer a resistance to a change of shape under the action of an external force. Viscosity varies greatly from one liquid to another. It approaches the conditions of a solid for highly viscous liquids and approaches a gas for the slightly viscous liquids. Viscosity decreases with rising temperatures. For example, #6 oil is a solid at low temperatures and begins to flow as it is heated. Water is perfectly elastic, compressing when pressure is imposed and returning to its original condition when the pressure is removed. The compressibility of water may be expressed as 1/K, where K is the coefficient of compressibility and is equal to 43,200,000 lb/ft2. It can be seen that if a pressure of 100 lb/ft2 were applied, the volumetric change would be 100∕43,200,000. The change is of such negligible significance that water is always treated as incompressible for all calculations in plumbing design. The temperature at which water boils varies with the pressure to which it is subjected. At sea level—14.7 psi—water boils at 212°F. At an elevation above sea level, where the atmospheric pressure is less than 14.7 psi, water will boil at a lower temperature. In a closed system, such as that found in the domestic hot water system where the pressure is generally around 50 psi above atmospheric pressure, the water will not boil until a temperature of 300°F is reached.

Types of Flow When water is moving in a pipe, two types of flow can exist. One type is known by the various names of streamline, laminar, or viscous. The second is called turbulent flow. At various viscosities (various temperatures), there is a certain critical velocity for every pipe size above which turbulent flow occurs and below which laminar flow occurs. This critical velocity occurs within a range of Reynolds numbers from approximately 2100 to 4000. Reynolds formula is: Equation 1

ρ Re = DV µgc

where Re = Reynolds number, dimensionless D = Pipe diameter, ft V = Velocity of flow, ft/sec ρ = Density, lbm/ft3 µ = Absolute viscosity, lbf · sec/ft2 gc = Gravitational constant, 32.2 lbm·ft/lbf·sec2 Within the limits of accuracy required for plumbing design, it can be assumed that the critical velocity occurs at a Reynolds number of 2100. In laminar flow, the roughness of the pipe wall has a negligible effect on the flow but the viscosity has a very significant effect. In turbulent flow, the viscosity has an insignificant effect but the roughness of the pipe wall has a very marked effect on the flow. Very rarely is a velocity of less than 4 ft/sec employed in plumbing design. The Reynolds number for a 3 in. pipe and a velocity of flow of 4 ft/sec would be

Re =

(0.250ft)(4ft/sec)(62.4lbm/ft3) = 82,500 (2.35 × 10–5 lbf·sec/ft2)(32.2 lbm·ft/lbf·sec2

(which is well above the critical number of 2,100) It can be seen that all plumbing design is with turbulent flow and only when very viscous liquids or extremely low velocities are encountered does the plumbing engineer deal with laminar flow. Critical velocities of ½, 1, and 2-in. pipe at 60°F are 0.61, 0.31, and 0.15 ft/sec, respectively, and at 140°F they are 0.25, 0.13, and 0.06 ft/sec, respectively.

Velocity of Flow When the velocity of flow is measured across the section of pipe from the center to the wall, it is found that there is a variation in the velocity, with the greatest velocity at the center and a minimum velocity at the walls. The average velocity for the entire cross-section is approximately 84% of the velocity as measured at the center. The plumbing engineer is concerned only with the average velocity, and all formulas are expressed in average velocity. Whenever and wherever the term velocity is used, it is the average velocity of flow that is meant. Since water is incompressible within the range of pressures met in plumbing design, a definite relationship can be expressed between the quantity flowing past a given point in a given time

Reprinted from Engineered Plumbing Design II, Chapter 11: “Flow in Water Piping,” by A. Calvin Laws, PE, CPD. © American Society of Plumbing Engineers. Plumbing Systems & Design

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and the velocity of flow. This can be expressed as (Equation 3- g = gravitational acceleration, 32.2 ft/sec2 Simpo PDF Merge and Split Unregistered Version - ghttp://www.simpopdf.com 2 2): c = gravitational constant, 32.2 lbm·ft/lbf·sec Q = AV V = velocity, ft/sec where When the body weighs 1 lb the formula becomes Q = quantity of flow (volumetric flow rate), ft3/sec Equation 6 A = cross-sectional area of flow, ft2 V2 EK = 2g V = velocity of flow, ft/sec c The units employed in this flow formula are inconvenient for where use in plumbing design. The plumbing engineer deals in gallons EK = kinetic energy per pound weight per minute and inches for pipe sizes. Converting to these terms, Static Head the flow rate becomes (Equation 8-8): At any point below the surface of water that is exposed to atmospheric pressure, the pressure (head) is produced by the weight q = 2.448 d2V of the water above that point. The pressure is equal and effective where in all directions at this point and is proportional to the depth q = quantity of flow (flow rate), gpm below the surface. This pressure is variously called static head, d = diameter of pipe, in. static pressure, hydrostatic head, or hydrostatic pressure. It is the V = velocity of flow, ft/sec measure of the potential energy. Because pressure is a function Potential Energy of the weight of the water, it is possible to convert the static head One of the most fundamental laws of thermodynamics is that expressed as feet of head into pounds per square inch. (See energy can be neither created nor destroyed; it can only be con- Table 2.) verted from one form to another. The energy of a body due to The pressure developed by the weight of a column of water 1 its elevation above a given level is called its potential energy in in.2 in cross-sectional area and h ft high may be expressed as relation to that datum. Work had to be performed to raise the body to that elevation and this work is equal to the product of Equation 7 γ × h p = 144 the weight of the body and the height it was raised. This can be expressed as: where p = pressure, lbf/in2 Equation 2 γ = specific weight of water, lbf/ft3 EP = w h = mgh gc h = static head, ft where At 50°F, the pressure expressed in pounds per square inch for EP = potential energy, ft lbf a 1-ft column of water is then: w = weight of the body, lbf h = height raised, ft g = gravitational acceleration, 32.2 ft/s2 Table 2 Heads of Water in Feet Corresponding to Pressure in Pounds per Square Inch gc = gravitational constant, 32.2 lbm·ft/ PSI 0 1 2 3 4 5 6 7 8 9 lbf·s2 0 2.3 4.6 6.9 9.2 11.6 13.9 16.2 18.5 20.8 10 23.1 25.4 27.7 30.0 32.3 34.7 37.0 39.3 41 .6 43.9 When the weight is equal to 1 lb the for20 46.2 48.5 50.8 53.1 55.4 57.8 60.1 62.4 64.7 67.0 mula becomes 30 69.3 71.6 73.9 76.2 78.5 80.9 83.2 85.5 87.8 90.1 Equation 3 40 92.4 94.7 97.0 99.3 101.6 104.0 106.3 108.6 110.9 113.2 50 115.5 117.8 120.1 122.4 124.7 127.1 129.4 131.7 134.0 136.3 EP = hg gc 60 138.6 140.9 143.2 145.5 147.8 150.2 152.5 154.8 157.1 159.4 where 70 161.7 164.0 166.3 168.6 170.9 173.3 175.6 177.9 180.2 182.5 EP = potential energy per pound weight 80 184.8 187.1 189.4 191.7 194.0 196.4 198.7 201.0 203.3 205.6 90 207.9 210.2 212.5 214.8 217.1 219.5 221.8 224.1 226.4 228.7 Kinetic Energy 100 231.0 233.3 235.6 237.9 240.2 242.6 244.9 247.2 249.5 251.8 The energy of a body due to its motion is 110 254.1 256.4 258.7 261.0 263.3 265.7 268.0 270.3 272.6 274.9 called kinetic energy and is equal to one-half 120 277.2 279.5 281.8 284.1 286.4 288.8 291.1 293.4 295.7 298.0 its mass and the square of its velocity. Mass 130 300.3 302.6 304.9 307.2 309.5 311.9 314.2 316.5 318.8 321.1 140 323.4 325.7 328.0 330.3 332.6 335.0 337.3 339.6 341.9 344.2 is equal to the weight of the body divided by 150 346.5 348.8 351.1 353.4 355.7 358.1 360.4 362.7 365.0 367.3 its acceleration imposed by gravity. 160 369.6 371.9 374.2 376.5 378.8 381.2 383.5 385.8 388.1 390.4 Equation 4 170 392.7 395.0 397.3 399.6 401.9 404.3 406.6 408.9 411.2 413.5 wgc m = g 180 415.8 418.1 420.4 422.7 425.0 427.4 429.7 432.0 434.3 436.6 c 190 438.9 441.2 443.5 445.8 448.1 450.5 452.8 455.1 457.4 459.7 Equation 5 200 462.0 464.3 466.6 468.9 471.2 473.6 475.9 478.2 480.5 482.8 2 wg 210 485.1 487.4 489.7 492.0 494.3 496.7 499.0 501.3 503.6 505.9 w × V2 EK = ½ × gc c × V = gc 2g 220 508.2 510.5 512.8 515.1 517.4 519.8 522.1 524.4 526.7 529.0 230 531.3 533.6 535.9 538.2 540.5 542.9 545.2 547.5 549.8 552.1 where 240 554.4 556.7 559.0 561.3 563.6 566.0 568.3 570.6 572.9 575.2 EK = kinetic energy, ft lbf 250 577.5 579.8 582.1 584.4 586.7 589.1 591.4 593.7 596.0 598.3 w = weight of body, lbf m = mass of the body, lbm

Notes: 1. To use the chart, find the point corresponding to the specific pressure (psi) by adding incremental values in the top line to the base values in the extreme left column. For example, to find head in ft. corresponding to 25 psi, follow the line of figures to the right of 20 psi and read 57.8 ft under 5 psi. 2. Head values in the body of the chart were calculated by multiplying psi by 2.31. To convert ft of head to psi, multiply by 0.433, or use the chart in reverse.

JULY/AUGUST 2007


CONTINUING EDUCATION: Flow in Water Piping 62.408

g = gravitational constant, 32.2 lbm·ft/lbf·sec2

c p =Merge × 1 = 0.433 lbf/in Simpo PDF Split Unregistered Version - http://www.simpopdf.com 144 and

2

Conversely, the height of a column of water that will impose a pressure of 1 lb/in.2 is

h = p × 144 γ 144 = 2.31 ft h = 1 × 62.408

The term Pgc/ρg is equal to the static head or height of the liquid column. Substituting in the equation it becomes Equation 12

To convert from feet of head to pounds per square inch, multiply the height by 0.433. To convert pounds per square inch to feet of head, multiply the pounds per square inch by 2.31.

Velocity Head

Zg + h + V2 = E T gc 2gc

For any two points in a system, we may then write: Equation 13

Z1g V12 Z2g V22 + h + = + h + 1 2 gc gc 2gc 2gc

Figure 1 illustrates the application of this equation.

In a piping system with the water at rest, the water has potential energy. When the water is flowing it has kinetic energy as well as potential energy. To cause the water to flow some of the available potential energy must be converted to kinetic energy. The decrease in the potential energy, or static head, is called the velocity head. In a freely falling body, the body is accelerated by the action of gravity at a rate of 32.2 ft/sec2. The height of the fall and the velocity at any moment may be expressed as: Equation 8

h = gt 2

2

Equation 9

Friction When water flows in a pipe, friction is produced by the rubbing of water particles against each other and against the walls of the pipe. This friction generates heat, which is dissipated in the form of a rise in the temperature of the water and the piping. This temperature rise in plumbing systems is insignificant and can safely be ignored in plumbing design. It requires a potential energy of 778 ft-lbf to raise 1 lb of water 1°F. The friction produced by flowing water also causes a pressure loss along the line of flow, which is called friction head. By utilizing Bernoulli’s equation this friction head loss can be expressed as:

V = gt or t = V g

where h = velocity head, ft t = time, sec g = gravitational acceleration, 32.2 ft/sec2 V = velocity, ft/sec Substituting t = V/g in the first equation,

Figure 11-1 Bernoulli's Theorem (Disregarding Friction)

2 g h = 2 × V2 g

Equation 10

V2 h = 2g

The foregoing illustrates the conversion of the potential energy of a body (static head) due to its height into kinetic energy (velocity head). The velocity head, V2/2g, is a measure of the decrease in static head expressed in feet of column of water.

Bernoulli’s Theorem As previously stated, energy can be neither created nor destroyed. Bernoulli developed an equation to express this conservation of energy as it is applied to a flowing liquid. The liquid is assumed to be frictionless and incompressible. Equation 11

Zg + Pgc + V2 = E T gc ρg 2gc

where ET = total energy ft·lbf/lbm Z = height of point above datum, ft P = pressure, lbf/ ft2 ρ = density, lbm/ft3 V = velocity, ft/sec g = gravitational acceleration, 32.2 ft./sec2 Plumbing Systems & Design

JULY/AUGUST 2007

Z1g V12 Z2g V22 gc + h1 + 2gc = gc + h2 + 2gc

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[

][

]

Figure 11-2 Toricelli's Theorem

Simpo Version - http://www.simpopdf.com Z1gPDF Merge V12 and Split Z2g Unregistered V22

hF =

gc

+ h1 +

2gc

Flow from Outlets

-

gc

+ h2 +

2gc

Experiments to determine the velocity of flow from an outlet in the side of an open tank were performed by Toricelli in the 17th century. The result of these experiments was expounded in the theorem: “Except for minor frictional effects, the velocity is the same as if the fluid had fallen freely from the surface through a vertical distance to the outlet.” This can be expressed as: Equation 15

V = √2gh

It is graphically shown in Figure 2. If friction, size, and shape of the opening and entrance losses are disregarded, the ideal velocity is the same as the maximum velocity and is equal to the velocity attained by free fall. The actual velocity, however, is always less than the ideal. All the factors, previously ignored, when taken into consideration can be expressed as the coefficient of discharge, CD. The actual velocity can then be written: Equation 16

V = CD √2gh

For most outlets encountered in a plumbing system an average coefficient of discharge of 0.67 can be safely applied.

Flow in Piping The velocity of flow at any point in a system is due to the total energy at that point. This is the sum of the potential and kinetic energy, less the friction head loss. The static head is the potential energy, but some of it was converted to kinetic energy to cause flow and some of it was used to overcome friction. It is for these reasons that the pressure during flow is always less than the static pressure. The pressure measured at any point while water is flowing is called the flow pressure. This is the pressure that is read on a pressure gauge installed in the piping. The kinetic energy of water flowing in a plumbing system is extremely small. Very rarely is the design velocity for water flow in plumbing systems greater than 8 ft/sec. The kinetic energy (velocity head) at this velocity is V2/2g or 8 ∕64.4. This is equal to 1 ft or 0.433 psi, which is less than 0.5 psi. It can be seen that such an insignificant pressure can be safely ignored in all calculations. The maximum rate of discharge from an outlet can now be determined from the flow pressure and the diameter of the outlet (using Equations 8-2 to 8-5):

d = diameter of outlet, in. V1 = ideal velocity, ft/sec h = flow pressure, ft p = flow pressure, psi If 0.67 is used for the coefficient of discharge, then, per Equation 6-1,

qD = 13.17d2 √h and

2

qD = CD q1 qD = CD × 2.448 d2V1 qD = CD × 2.448d2 √2gh qD = CD × 19.65d2 √h or Equation 17

qD = CD × 29.87d2 √p

where qD = actual quantity of discharge, gpm q1 = ideal quantity of discharge, gpm CD = coefficient of discharge, dimensionless

Equation 18

qD = 20d2 √p

Friction in Piping As stated previously, whenever flow occurs, there is a continuous loss of pressure along the piping in the direction of flow. The amount of this head loss because of friction is affected by 1. 2. 3. 4.

Density and temperature of the fluid Roughness of the pipe Length of run Velocity of the fluid

Experiments have demonstrated that the friction head loss is inversely proportional to the diameter of the pipe, proportional to the roughness and length of the pipe, and varies approxi-

JULY/AUGUST 2007


CONTINUING EDUCATION: Flow in Water Piping mately with the square of the velocity. Darcy expressed this rela- Equation 24 Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com tionship as: q = 40.1 d2½ 2 h = fLV or D × 2g

Equation 19

ρfLV2 p = 144D × 2g c

where h = friction head loss, ft p = friction head loss, lbf/in2 ρ = density of fluid, lbm/ft3 f = coefficient of friction, dimensionless L = length of pipe, ft D = diameter of pipe, ft V = velocity of flow, ft/sec gc = gravitational constant, 32.2 lbm ft/lbf sec2 Values for the coefficient of friction are given in Table 3. It can be seen from Table 3 that steel pipe is much rougher than brass, lead or copper. It follows that there will be a greater head loss in steel pipe than in the other material. Table 3 Average Values for Coefficient of Friction, f Nominal Brass, Copper, Galvanized Pipe Size, in. or Lead Iron or Steel ½ 0.022 0.044 ¾ 0.021 0.040 1 0.020 0.038 1¼ 0.020 0.036 1½ 0.019 0.035 2 0.018 0.033 2½ 0.017 0.031 3 0.017 0.031 4 0.016 0.030

For ease of application for the plumbing engineer, the formula for friction head loss can be reduced to a simpler form. Assuming an average value for the coefficient of friction of 0.02 for brass and copper and 0.04 for steel, the formula becomes: For brass and copper Equation 20 Equation 21

h = 0.000623q2 × L5 d p = 0.00027q2 × L5 d

Equation 25 and for steel Equation 26 Equation 27

( hL )

½

( )

q = 60.8 d2½ p L

½

( )

q = 28.3 d2½ h L

½

( )

q = 43.0 d2½ p L

where q = quantity of flow, gpm d = diameter of pipe, in. h = pressure, ft p = pressure, psi L = length of pipe, ft

½

The terms h/L and p/L represent the loss of head due to friction for 1 ft of pipe length and is called the uniform friction loss. Values of d2½ for various diameters of pipe and various materials are given in Table 4. In all water flow formulas, the term L (length of run in feet) is always the equivalent length of run (ELR).Every fitting and valve imposes more frictional resistance than the pipe itself.To take this additional friction head loss into account, the fitting or valve is converted to an equivalent length of pipe of the same size that will impose an equal friction loss, e.g., a 4-in. elbow is equivalent to 10 ft of 4-in. pipe.Thus, if the measured length of run of 4-in. piping with one elbow is 15 ft, then the equivalent length of run is 15 + 10 = 25 ft.The length of pipe measured Table 4 Values of d2½ Nominal Brass or Size, In. Copper Pipe ½ 0.31 ¾ 0.61 1 1.16 1¼ 2.19 1½ 3.24 2 6.17 2½ 9.88 3 16.41 4 32.00

Copper Copper Galvanized Type K Type L Iron or Steel 0.20 0.22 0.31 0.48 0.55 0.62 0.99 1.06 1.13 1.73 1.80 2.24 2.67 2.78 3.29 5.37 5.55 6.14 9.25 9.54 9.58 14.41 14.87 16.48 29.23 30.13 32.53

and for steel

Table 5 Equivalent Pipe Length for Valves and Fittings Gate Nominal Valve Angle Globe Swing L 2 h = 0.00124q × 5 Pipe Size Full Valve Full Valve Full Check Full d inches Open Open Open Open Equation 23 ½ 0.35 9.3 18.6 4.3 p = 0.00539q2 × L5 ¾ 0.44 11.5 23.1 5.3 d 1 0.56 14.7 29.4 6.8 These formulas can be rearranged in another 1¼ 0.74 19.3 38.6 8.9 useful form: 1½ 0.86 22.6 45.2 10.4 For brass and copper 2 1.10 29.0 58.0 13.4 2½ 1.32 35.0 69.0 15.9 3 1.60 43.0 86.0 19.8 4 2.10 57.0 113.0 26.0 5 2.70 71.0 142.0 33.0 6 3.20 85.0 170.0 39.0 8 4.30 112.0 224.0 52.0 Equation 22


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45° Elbow 0.78 0.97 1.23 1.6 1.9 2.4 2.9 3.6 4.7 5.9 7.1 9.4

Long Sweep Elbow or Run of Tee 1.11 1.4 1.8 2.3 2.7 3.5 4.2 5.2 6.8 8.5 10.2 13.4

Std. Elbow 1.7 2.1 2.6 3.5 4.1 5.2 6.2 7.7 10.2 12.7 15.3 20.2

Std. Tee Thru Side Outlet 3.3 4.2 5.3 7.0 8.1 10.4 12.4 15.5 20.3 25.4 31.0 40.0

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along the centerline of pipe and fittings is the developed length. Simpo PDF Merge and Split Unregistered Version Table 5 shows equivalent lengths of pipe for valves and fittings of various sizes. Note that the larger the pipe size, the more significant the equivalent length of run becomes. In the design phase of piping systems, the size of the piping is not known and the equivalent lengths cannot be accurately determined. A rule of thumb that has worked exceptionally well is to assume 50% of the developed length as an allowance for fittings and valves. Once the sizes are determined, the accuracy of the assumption can be checked. All equipment imposes a friction head loss and must be carefully considered in the design and operation of a system. The pressure drop through any piece of equipment can be obtained from the manufacturer. The knowledgeable engineer is careful to specify the maximum pressure drop he/she will permit through a piece of equipment.


JULY/AUGUST 2007



Now Online!

The technical article you must read to complete the exam is located at www.psdmagazine.org. The following exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

About This Issue’s Article

The July/August 2007 continuing education article is “Flow in Water Piping,” Chapter 11 of Engineered Plumbing Design II by A. Cal Laws, PE, CPD. This chapter discusses hydraulics, which can be defined as the study of the principles and laws that govern the behavior of liquids at rest or in motion, hydrostatics, the study of liquids at rest, and hydrokinetics, or the study of liquids in motion. Although this text deals exclusively with water, all the data developed can be applied to any liquid. The chapter delves into the physical properties of water, types of flow, Bernoulli’s and Toricelli’s Theorems, and friction in piping as they relate to sizing piping systems. It provides calculations for finding the Reynolds number, velocity of flow, potential and kinetic energy, pressure, velocity head, and Bernoulli’s Theorem, among others. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Flow in Water Piping” (PSD 140) 1. The average coefficient of friction (f) in a 2-inch steel pipe is _________. a. 0.037 b. 0.035 c. 0.033 d. 0.031 2. Friction is created by the flow of water in piping. This friction generates _________. a. pressure drop b. pressure increase c. heat d. none of the above 3. Number six (6) oil _________. a. is not part of this chapter b. is a solid at low temperatures c. begins to flow when heated d. b and c only

PSD 140


7. How much potential energy is required to raise 1 pound of water 1°F? a. 728 ft-lbf, b. 778 ft-lbf, c. 828 ft-lbf, d. 878 ft-lbf

8. The pressure at any point below the surface of water exposed to atmospheric pressure is referred to as ______. a. static head b. hydrostatic pressure c. specific pressure d. a or b 9. What is the equivalent pipe length for a 4-inch fully open globe valve? a. 113.0 b. 142.0 c. 170.0 d. 224.0

4. Water is _________. a. not compressible b. perfectly elastic c. greatly compressible d. none of the above

10. The critical velocity of water _________. a. in ½-inch, 1-inch, and 2-inch pipe is less than 0.5 fps at temperatures of 60°F to 140°F b. is represented by a Reynolds number of 82,500 c. is Re=DVp/ugc d. is greater than 20 ft/sec for all pipe 10 inches and smaller at temperatures of 60°F to 140°F

5. Experiments to determine the velocity of flow from an outlet were performed by _________ in the 17th century. a. Bernoulli b. Reynolds c. Toricelli d. Hunter

11. The static pressure is always _________ the pressure during flow. a. less than b. greater than c. the same as d. none of the above

6. Velocity head (V2/2g) _________. a. is a measure of the decrease in static head b. is of no consequence to the plumbing engineer c. must be understood to control water hammer d. is responsible for most pipe fitting failures

12. Water in motion _________. a. has used its potential energy b. has only kinetic energy c. has both kinetic and potential energy d. none of the above


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Simpo PDFSystems Merge and Unregistered Version - http://www.simpopdf.com Plumbing &Split Design Continuing Education Application Form This form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who ear a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required). 1. Photocopy this form or download it from www.psdmagazine.org. 2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space. 3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form. 4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656) or fax (773-695-9007). Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________


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Signature

Flow in Water Piping (PSD 140)

Questions appear on page . Circle the answer to each question. Q 1. A B C D Q 2. A B C D Q 3. A B C D Q 4. A B C D Q 5. A B C D Q 6. A B C D Q 7. A B C D Q 8. A B C D Q 9. A B C D Q 10. A B C D Q 11. A B C D Q 12. A B C D


Expiration date


Appraisal Questions Flow in Water Piping (PSD 140) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No 6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________ 1. 2. 3. 4. 5.

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Fuel Gas Piping Systems

PSD 144


Continuing Education from Plumbing Systems & Design Diane M. Wingard, CPD

JANUARY/FEBRUARY 2008

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Fuel Gas Piping Systems


LOW AND MEDIUM-PRESSURE NG SYSTEMS This chapter describes fuel-gas systems on consumer sites from the property line to the final connection with the most remote gas appliance or piece of equipment. The system is intended to provide sufficient pressure and volume for all uses. Since NG is a nonrenewable energy resource, the engineer should design for its efficient use. The direct utilization of NG is preferable to the use of electrical energy when electricity is obtained from the combustion of gas or oil. However, in many areas, the gas supplier and /or governmental agencies may impose regulations that restrict the use of natural gas. Refer to the chapter “Energy Conservation in Plumbing Systems” in Plumbing Engineering Design Handbook Volume 1 for information on appliance efficiencies and energy conservation recommendations. The composition, specific gravity, and heating value of NG (NG) vary depending on the well (or field) from which the gas is gathered. NG is a mixture of gases, most of which are hydrocarbons, and the predominant hydrocarbon is methane. Some natural gases contain significant quantities of nitrogen, carbon dioxide, or sulfur (usually as H2S). Natural gases containing sulfur or carbon dioxide are apt to be corrosive. These corrosive substances are usually eliminated by treatment of the NG before it is transmitted to the customers. Readily condensable petroleum gases also are usually extracted before the NG is put into the pipeline to prevent condensation during transmission. The physical properties of both NG and liquefied

petroleum gas (LPG) are given in Table 1. NG and LPG are colorless and odorless, so an additive is added to the gases to detect a leak.

General NG is obtained from a franchised public utility obligated to provide gas to all who request this service. There are different types of services a utility may provide, each with a different cost. They include the following: 1. Firm Service. This service provides constant supply of gas under all conditions. 2. Interruptible Service. This service allows the utility to stop gas supply under certain conditions and proper notification and to start service when the conditions no longer exist. The most common reason for this interruption is when the ambient temperature falls below a predetermined point. 3. Light or Heavy Process Service. This service is provided for process or other industrial use. The quantity of gas must meet utility company requirements. 4. Commercial or Industrial Service. This type of service is used for heating and cooling loads for this class of building. 5. Transportation Gas Service. This is used when the gas is purchased directly from the producer (or wellhead) and not directly from the utility company. The gas actually is carried in the utility company mains, and there is a charge for this use. There are many gases used as a fuel gas. Where easily and cheaply available, two major fuel gases, NG and LPG, are preferred. Other gases are used because of availability. For properties of gases commonly available throughout the world, refer to Table 2.

Approvals

Table 1 Average Physical Properties of Natural Gas and Propane Formula Molecular weight Melting (or freezing) point, °F Boiling point, °F Specific gravity of gas (air = 1.00) Specific gravity of liquid 60°F/60°F (water = 1.00) Latent heat of vaporization at normal boiling point, Btu/lb Vapor pressure, lb/in2, gauge at 60°F Pounds per gallon of liquid at 60°F Gallons per pound of liquid at 60°F Btu per pound of gas (gross) Btu per ft3 gas at 60°F and 30 in mercury Btu per gallon of gas at 60°F Cubic feet of gas (60°F, 30 in Hg)/gal of liquid Cubic feet of gas (60°F, 30 in Hg)/lb of liquid Cubic feet of air required to burn 1 ft3 gas Flame temperature, °F Octane number (isooctane = 100) Flammability limit in air, upper Flammability limit in air, lower

Propane C3H8 44.097 – 305.84 – 44 1.52 0.588 183 92 4.24 0.237 21591 2516 91547 36.39 8.58 23.87 3595 125 9.50 2.87

Natural gas (methane) CH4 16.402 – 300.54 – 258.70 0.60 0.30 245 2.51 23000 1050 ± 59.0 23.6 9.53 3416 15.0 5.0

The American Gas Association, the National Fire Protection Association, and the American National Standards Association do not approve, inspect, or certify installations, procedures, equipment, or materials. The acceptability of all such items must comply with the authority having jurisdiction (AHJ).

System Operating Pressure The gas pressure in the piping system downstream of the meter is usually 5 to 14 in. (125 to 356 mm) of water column (wc). Under these conditions, good engineering practice limits the pressure losses in the piping to a range between 0.2 to 0.5 in. (5 to 13 mm) wc. However, local codes may dictate a more stringent pressure drop maximum; these should be consulted before the system is sized. Most appliances require approximately 3.5 in. (89 mm) wc. The designer must be aware that large appliances, such as boilers, may require high gas pressures to operate properly. Where appliances require high pressures or where long distribution lines are involved, it may be necessary to use higher pressures at the meter outlet to satisfy the appliance requirements or provide for greater pressure losses in the piping system, thereby allowing economy of pipe size. Systems often are designed with meter outlet pressures of 3 to 5 psi (20.7 to 34.5 kPa) and with pressure regulators to reduce the pressure for appliances as required. A

Reprinted from Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems, Chapter 7: “Fuel Gas Piping Systems.” © American Society of Plumbing Engineers , 2005.



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Table 2 Physical and Combustion Properties of Commonly Available Fuel Gases Heating value Specific Btu/ft3 Btu/lb Heat release, Btu Specific Density, volume No. Gas Gross Net Gross Net Per ft3 air Per lb air gravity lb per ft3 ft3/lb 1 Acetylene 1,498 1,447 21,569 20,837 125.8 1677 0.91 0.07 14.4 2 Blast furnace gas 92 92 1,178 1,178 135.3 1804 1.02 0.078 12.8 3 Butane 3,225 2,977 21,640 19,976 105.8 1411 1.95 0.149 6.71 4 Butylene (hutene) 3,077 2,876 20,780 19,420 107.6 1435 1.94 0.148 6.74 5 Carbon monoxide 323 323 4,368 4,368 135.7 1809 0.97 0.074 13.5 6 Carburetted water gas 550 508 11,440 10,566 119.6 1595 0.63 0.048 20.8 7 Coke oven gas 574 514 17,048 15,266 115.0 1533 0.44 0.034 29.7 8 Digester (sewage) gas 690 621 11,316 10,184 107.6 1407 0.80 0.062 16.3 9 Ethane 1,783 1,630 22,198 20,295 106.9 1425 1.05 0.080 12.5 10 Hydrogen 325 275 61,084 51,628 136.6 1821 0.07 0.0054 186.9 11 Methane 1,011 910 23,811 21,433 106.1 1415 0.55 0.042 23.8 12 Natural (Birmingham, AL) 1,002 904 21,844 19,707 106.5 1420 0.60 0.046 21.8 13 Natural (Pittsburgh, PA) 1,129 1,021 24,161 21,849 106.7 1423 0.61 0.047 21.4 14 Natural (Los Angeles, CA) 1,073 971 20,065 18,158 106.8 1424 0.70 0.054 18.7 15 Natural (Kansas City, MO) 974 879 20,259 18,283 106.7 1423 0.63 0.048 20.8 16 Natural (Groningen, Netherlands) 941 849 19,599 17,678 111.9 1492 0.64 0.048 20.7 17 Natural (Midlands Grid, U.K.) 1,035 902 22,500 19,609 105.6 1408 0.61. 0.046 21.8 18 Producer (Wellman-Galusha) 167 156 2,650 2,476 128.5 1713 0.84 0.065 15.4 19 Propane 2,572 2,365 21,500 19,770 108 1440 1.52 0.116 8.61 20 Propylene (Propane) 2,332 2,181 20,990 19,030 108.8 1451 1.45 0.111 9.02 21 Sasol (South Africa) 500 443 14,550 13,016 116.3 1551 0.42 0.032 31.3 22 Water gas (bituminous) 261 239 4,881 4,469 129.9 1732 0.71 0.054 18.7


majority of times, the utility company will reduce the incoming pressure to a figure that is requested by the design engineer at the start of the project. The maximum allowable operating pressure for NG piping systems inside a building is based on NFPA 54: National Fuel Gas Code, except when approved by the AHJ or when insurance carriers have more limiting requirements. NG systems are not permitted to have more than 5 psig (34.5 kPa) unless all the following are met: 1. The AHJ will allow a higher pressure. 2. The distribution piping is welded. 3. Pipe runs are enclosed for protection and located in a ventilated place that will not allow gas to accumulate. 4. The pipe is installed in areas only used for industrial processes, research, warehouse, or mechanical equipment rooms. The maximum LPG pressure of 20 psig (138 kPa) is allowed, provided the building is used only for research or industrial purposes and is constructed in accordance with NFPA 58: Liquefied Petroleum Gas Code, Chapter 7.

Efficiency The difference between the input and the output of any equipment is the heat lost in the burner, the heat exchanger, and the flue gases. Water heating and space heating equipment are usually 75 to 85% efficient, and ratings are given for both input and output. Cooking and laundry equipment also is usually 75 to 85% efficient, and ratings are given for the input that take into consideration the internal losses. When only the output required for the appliance is known, it will be necessary to increase the volume of gas to account for the loss of efficiency.

Codes and Standards The local code in the area where the project is located is the primary code to be used. Often, this code refers to NFPA 54. Other codes and standards that may be applicable are ANSI/NFPA 30: Flammable and Combustible Liquids Code, ANSI/NFPA 58, ANSI Z83.3: Gas Utilization Equipment for Large Boilers, ANSI/UL 144: Pressure Regulating Valves for LPG, NFPA 88A: Standard for Parking Structures, and American Gas Association standards. Insurance carriers such as Industrial Risk Insurers and FM Global also have standards, which may be in many respects stricter than the applicable code.

Gas Meters Meters are required in all services. To achieve greatest accuracy, the pressure into the meter must be regulated. Requirements for various utilities differ regarding the placement and arrangement of the meter assembly. The assembly could consist of filters, valves, regulators, and relief valves. It could be placed indoors, on a slab outdoors aboveground, or underground in an outdoor pit. The plumbing contractor is usually responsible for a pit, if required, a slab, telephone outlet, and electrical outlet adjacent to the meter. The utility company almost always supplies the meter. The utility company usually runs the service on the consumer’s site up to the meter, terminating with a shutoff valve.

Pressure Regulating Valves A pressure regulator is a device for reducing a variable high inlet pressure to a constant lower outlet pressure. The line regulator is used to reduce supply line pressure from generally 25–50 psig (170–345 kPa) to an intermediate pressure of about 3–5 psig (21–35 kPa). If used, it is usually placed outside before the meter and selected by the utility company. If installed inside the building, a relief vent will be necessary. An intermediate regulator is used to JANUARY/FEBRUARY 2008


CONTINUING EDUCATION: Fuel Gas Piping Systems further reduce the pressure from 3–5 psig (21–35 kPa) to one that to design and specify gas vents. This is done by either the HVAC Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com can be used by terminal equipment, which is approximately 7 in. department or the manufacturer. (178 mm) wc. Different types of valves may require a relief vent. An Where the ratings of the appliances are not known, they shall appliance regulator connects the supply to the terminal equipment comply with the typical demand of appliances by types as indicated and may be provided by the equipment manufacturer, usually on in NFPA 54. gas trains where equipment has one. Types of appliance regulaAllowable Gas Pressure tors are a zero governer, a backpressure regulator, and a differential The gas outlet pressure in the piping system downstream of the regulator. meter that is supplied by the utility is mostly in the range of 4–14 When regulators are installed inside a building and require a in. (102–356 mm) wc, with approximately 7 in. (178 mm) wc being vent, these vents often must be routed to the atmosphere. The vents a common figure. Good engineering practice limits the pressure from individual regulators may not be combined. When bottled gas losses in the piping to approximately 0.2–0.5 in. (5–12.7 mm) wc is used, the tank can have as much as 150 psi (1034.6 kPa) pressure depending on the outlet pressure, with 0.3 in. (7.6 mm) wc being to be reduced to the burner design pressure of 11 in. (279.4 mm) the most commonly used number. However, local codes may dicwc. The regulator normally is located at the tank for this pressure tate a more stringent pressure drop maximum. The AHJ should reduction. be consulted before the system is sized. Most appliances require Pressure Control Valves approximately 3.5 in. (89 mm) wc; however, the designer must be An excess flow valve is a device that shuts off the flow of gas if there is a much larger flow through the pipe or service than designed Table 3 Approximate Gas Demand for Common Appliances a for. In some parts of the country, particularly in areas where earthInput, quakes may occur, excessive flow valves are necessary to guard Appliance Btu/h (mJ/h) against the possibility of a break during such an event. In other Commercial kitchen equipment cases, where danger exists for equipment such as large boilers, Small broiler 30,000 (31.7) installation should be considered. Large broiler 60,000 (63.3) A low pressure cutoff shall be installed between the meter and Combination broiler and roaster 66,000 (69.6) appliance where the operation of a device, such as a gas compressor, appliance, or a boiler, could produce a vacuum or dangerous Coffee maker, 3-burner 18,000 (19) vacuum condition in the piping system. Coffee maker, 4-burner 24,000 (25.3)

Deep fat fryer, 45 lb (20.4 kg) of fat Deep fat fryer, 75 lb (34.1 kg) of fat Doughnut fryer, 200 lb (90.8 kg) of fat 2-deck baking and roasting oven 3-deck baking oven Revolving oven, 4 or 5 trays Range with hot top and oven Range with hot top Range with fry top and oven Range with fry top Coffee urn, single, 5-gal (18.9 L) Coffee urn, twin, 10-gal. (37.9 L) Coffee urn, twin, 15-gal (56.8 L) Stackable convection oven, per section of oven Residential equipment Clothes dryer (Type I) Range Stove-top burners (each) Oven 30-gal (113.6-L) water heater 40 to 50-gal (151.4 to 189.3-L) water heater Log lighter Barbecue Miscellaneous equipment Commercial log lighter Bunsen burner Gas engine, per horsepower (745.7 W) Steam boiler, per horsepower (745.7 W)

Appliance Control Valves An appliance shutoff valve shall be installed at all gas appliances prior to any flexible hose used to connect the appliance to the building gas supply.

Interlocks An automatic interlock, connected to the automatic fire extinguishing system, is required to shut off the gas supply to all equipment in a kitchen when there is a discharge in the event of a fire. In earthquake-prone areas, an interlock is required to shut off the supply of gas if the disturbance may rupture the pipe or separate pipe from any equipment.

Appliances Appliances are listed by types and categories that shall be used in the design of vents. These vents shall be sized and located in accordance with NFPA 54. Most manufacturers of gas appliances rate their equipment by the gas consumption values that are used to determine the maximum gas flow rate in the piping. Table 3 shows the approximate gas consumption for some common appliances. To find the flow rate of gas required, use the consumption from the manufacturer and divide by 1,000. If the equipment is a water heater, multiply the figure by the weight of water (8.48 lbs). The products of combustion from an appliance must be safely exhausted to the outside. This is accomplished with a gas vent system in most cases. Where an appliance has a very low rate of gas consumption (e.g., Bunsen burner or countertop coffee maker) or where an appliance has an exhaust system associated with the appliance (e.g., gas clothes dryer or range) and the room size and ventilation are adequate, a separate gas vent system may not be required. Current practice usually dictates the use of factory-fabricated and listed vents for small to medium-size appliances. Large appliances and equipment may require specially designed venting or exhaust systems. It is not the plumbing engineer’s responsibility

Commercial clothes dryer (Type 2) a



50,000 (52.8) 75,000 (79.1) 72,000 (76) 100,000 (105.5) 96,000 (101.3) 210,000 (221.6) 90,000 (95) 45,000 (47.5) 100,000 (105.5) 50,000 (52.8) 28,000 (29.5) 56,000 (59.1) 84,000 (88.6) 60,000 (63.3) 35,000 (36.9) 65,000 (68.6) 40,000 (42.2) 25,000 (26.4) 30,000 (31.7) 50,000 (52.8) 25,000 (26.4) 50,000 (52.8) 50,000 (52.8) 5,000 (5.3) 10,000 (10.6) 50,000 (52.8) See manufacturer’s data.

The values given in this table should be used only when the manufacturer’s data are not available.

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aware that large appliances, such as boilers, may require higher roof and away from doors, windows, and fresh-air intakes. It also Simpo to PDF Merge andWhere Splitappliances Unregistered Versionshould - http://www.simpopdf.com gas pressures operate properly. require higher be located on a side of the building that is not protected pressures or where long distribution lines are involved, it may be from the wind. Refer to NFPA 54 and local codes for vent locations. necessary to use higher pressures at the meter outlet to satisfy Altitude Derating Factor the appliance requirements or provide for greater pressure losses NG has a reduced density at a higher altitude that must be allowed in the piping system. If greater pressure at the meter outlet can for when the project location is more than 2,000 feet above sea level. be attained, a greater pressure drop can be allowed in the piping This altitude correction factor shall be multiplied by the gas input at system. If the greater pressure drop design can be used, a more ecosea level to determine the correct input at full load capacity. Refer nomical piping system is possible. to Figure 1 to determining the derating factor for NG.

Laboratory Usage NG is the primary gas used in laboratories at lab benches for Bunsen burners. Where NG is not available, propane gas is used, but this generally requires the manufacturer to be advised due to the Bunsen burner requiring a smaller orifice. Typical Bunsen burners consume either 5 cfh (0.15 m3/h) (small burners) or 10 cfh (0.30 m3/h) (large burners).The maximum pressure at the burner should not exceed 14 in. (355.6 mm) wc. 10 cfh (0.30 m3/h) is more commonly used. Some local codes require laboratory gas systems, especially those in schools or universities, to be supplied with emergency gas shutoff valves on the supply to each laboratory. The valve normally should be closed and opened only when the gas is being used. It should be located inside the laboratory and used in conjunction with shutoff valves at the benches or equipment, which may be required by other codes. The designer should ensure locations meet local code requirements. The following diversities, found in Table 4, shall be applied where flow will be from Bunsen burners:

Table 4 Laboratory Diversity Factors Laboratory Number of Diversity Flow3 cfh Outlets Factor (m /h) 1–8 100 9 (0.26) 9–16 90 15 (0.43) 17–29 80 24 (0.68) 30–79 60 48 (1.36) 80–162 50 82 (2.32) 163–325 45 107 (3.03) 326–742 40 131 (3.71) 743–1,570 30 260 (7.36) 1,571–2,900 25 472 (13.37) 2,901 and up 20 726 (20.56) Branch piping that serves one or two laboratory classrooms should be sized for 100% usage regardless of the number of outlets. Use factors should be modified to suit special conditions and must be used with judgment after consultation with the owner and /or user.

Gas Regulator Relief Vents Guidelines for the use of relief vents from pressure regulators, also referred to as gas-train vents, can be found in the latest editions of NFPA 54 and FM Global Loss Prevention Data Sheet 6-4: Oil- and Gas-Fired Single-Burner Boilers, as well as in other publications of industry standards, such as those issued by Industrial Risk Insurers and the American Gas Association. It should be noted that when the pressure regulators discharge, large amounts of fuel gas may be released. It is not uncommon for a local fire department to be summoned to investigate an odor of gas caused by a gas-train vent discharge. Every attempt should be made to locate the terminal point of the vents above the line of the

Figure 1 Altitude Correction Factor

The Altitude Correction Factor (ACF) should be multiplied by the gas input at sea level to determine the corrected input. Sizing of the equipment is then performed utilizing this corrected input multiplied by the full load efficency.

Piping System Materials The following piping materials are the most often used for both NG and propane. Pipe Steel (galvanized, plastic-wrapped, or black), brass, and copper. Black steel is the most commonly used pipe. Cast-iron pipe shall not be used. Tubing Semi-rigid copper type K or L. Plastic pipe and tubing (polyethylene) Plastic pipe may be used outside and underground only.

Flexible hose Corrugated stainless steel tubing Indoor Indoor gas hose connectors may be used with laboratory or shop and other equipment that requires mobility during operation or installation, if listed for this application. A shutoff valve must be installed where the connector is attached to the building piping. The connector must be of minimum length but shall not exceed 6 ft (1.8 m). The connector must not be concealed and must not extend from one room to another nor pass through wall partitions, ceilings, or floors. Outdoor Outdoor gas hose connectors may be used to connect portable outdoor gas-fired appliances, if listed for this application. A shutoff valve or a listed quick-disconnect device must be installed where the connector is attached to the supply piping and in such a manner as to prevent the accumulation of water or foreign matter. JANUARY/FEBRUARY 2008


CONTINUING EDUCATION: Fuel Gas Piping Systems This connection must be made only in the outdoor area where the Gas boosters for natural or liquefied petroleum gas Boosters Simpo Merge and Split Unregistered Versionfor- http://www.simpopdf.com appliance is toPDF be used. natural or utility-supplied gas are hermetically sealed and are Fittings and joints for low-pressure piping, 3 psi (21 kPa) or equipped to deliver a volumetric flow rate (user defined but within less Steel pipe may be threaded, flanged, or welded. Cast or mal- the booster’s rated capacity) to an elevated pressure beyond the leable iron threaded fittings are the most commonly used. Tubing supply pressure. The outlet pressure usually remains at a constant may be soldered or brazed using wrought copper or copper alloy differential above the supply pressure within a reasonable range. fittings and no flux. Brazing alloy must not contain phosphorous. The discharge pressure is the sum of the incoming gas pressure and Fittings and joints for high pressure piping greater than 3 psi the booster-added pressure at the chosen flow rate. The incoming (21 kPa) Steel pipe and fittings 4 in. (100 mm) and larger shall be gas pressure usually has an upper safety limit as stipulated by the welded. hermetic gas booster manufacturer. Therefore, in the engineering Tubing joints Tubing usually is needed for the flexible connec- literature from the manufacturer, the engineer may find cautions tions to equipment. For pressures normally encountered in the uti- or warnings about the upper limits of incoming pressure, usually lization of NG and LPG, the most often used joints are screwed. about 5 psi (34.5 kPa).

Design Considerations

Materials of construction

The fact that LPG vapors are heavier than air has a practical bearing on several items. For one thing, LPG systems are located in such a manner that the hazard of escaping gas is kept at a minimum. Since the heavier-than-air gas tends to settle in low places, the vent termination of relief valves must be located at a safe distance from openings into buildings that are below the level of such valves. With many gas systems, both the gas pressure regulator and the fuel containers are installed adjacent to the building they serve. This distance must be a least 3 ft (0.91 m) measured horizontally. However, the required clearances vary according to the tank size and the adjacent activities. The designer should refer to the local code and NFPA 54 for these clearances. When LPG piping is installed in crawl spaces or in pipe tunnels, the engineer may consider a sniffer system, which automatically shuts down the gas supply, sounds an alarm, and activates an exhaust system to purge the escaping gas from the area upon detection of gas in the space due to a breach in the piping system.

Housing and rotor Boosters used for fuel gas must be Underwriters Laboratories (UL) listed for the specific duty intended and shall be hermetically sealed. Casings on standard boosters usually are constructed of carbon steel, depending on the equipment supplier. Booster casings are also available in stainless steel and aluminum. Inlet and outlet connections are threaded or flanged, depending on the pipe size connection and the manufacturer selected, and the casings are constructed leak tight. Drive impellers are contained within the casing and always manufactured of a spark-resistant material such as aluminum. Discharge-type check valves are furnished on the booster inlet and on the booster bypass. It is important that these valves are listed and approved for use on the gas service at hand. The fan, control panel, valves, piping, and interelectrical connections can be specified as a skid-mounted package at the discretion of the designer. This allows for UL listing of the entire package rather than of individual components. Electrical components Motor housings for gas booster systems are designed for explosion-proof (XP) construction and are rated per National Electrical Manufacturers Association (NEMA) Class 1, Division 1, Group D classification with thermal overload protection. A factory UL-listed junction box with a protected, sealed inlet is necessary for wiring connections.

GAS BOOSTERS A gas booster is a pump that increases the pressure of gas. It is used when there is insufficient pressure available from the gas utility or LPG storage device to supply the necessary pressure to the equipment at hand. It is important to note that the gas service must be capable of the volumetric flow rate required at the boosted level. A booster cannot overcome an inadequate volumetric supply.

Figure 2 Variations of a Basic Simplex Booster System: (A) Standby Generator Application with Accumulator Tank Having a Limitation on Maximum Pressure 6 Plumbing Systems & Design


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(B)

(C) Figure 2 Variations of a Basic Simplex Booster System: (B) Dual Booster System for Critical Systems Like Those in Hospitals, (C) Heat Exchanger Loop Example—Required for High Flow Range with Low Minimum Flow. Other electrical ancillary equipment Boosters are equipped with low pressure switches that monitor the incoming gas pressure. The switch is designed to shut down the booster should the utilitysupplied pressure fall below a preset limit. The set point is usually about 3 in. (76 mm) wc, but the designer should verify the limit with the local gas provider. The switch must be UL listed for use with the gas service at hand. When the switch opens, it de-energizes the motor control circuit and simultaneously outputs both audible and visual signals, which require manual resetting. The booster can be equipped with an optional high/low gas pressure switch. This feature equips the booster to run only when adequate supply pressure

is available. The switch shuts the booster down at the maximum discharge setpoint pressure at the output line pressure. Minimum gas flow Gas boosters normally require a minimum gas flow that serves as an internal cooling medium. For example, a booster sized at a flow rate of 10,000 cfh (283.2 m3/h) has an inherent minimum turndown based on the minimum flow required to cool the unit. This rate, in the example, may be 2,000 cfh (566.3 m3/h) (see Figure 2). Should the unit be required to run below this turndown rate, additional supplemental cooling systems must be incorporated into the booster design. The heat exchangers normally rated for this use are water cooled. JANUARY/FEBRUARY 2008


CONTINUING EDUCATION: Fuel Gas Piping Systems Intrinsic safety Electrical connections are made through a Simpo PDF Merge andtoSplit Unregistered Version sealed, explosion-proof conduit the XP junction box on the booster unit. Control panels are rated NEMA 4 for outdoor use and NEMA 12 for indoor use unless the booster system is to be located in a hazardous area, which may have additional requirements. The panel, as an assembly, must display a UL label specific for its intended use. 4.

Gas laws for boosters Pressure/volume relationships The gas laws apply to the relationship of the incoming gas supply and the boosted service. The standard law for compressed gas relationships is as follows:

Equation 1 PV = RT where P = Pressure, psi or in. wc (kPa or mm wc) V = Volume, cfh (m3/h) R = Constant for the gas/air mixture used T = Temperature, °F (°C) Usually the temperature of the gas remains relatively constant and can be ignored in the relationship. Therefore, the pressure times the volume is proportional to a constant R. Further, the pressure/volume ratios before and after the booster are proportional, that is:

Equation 2 P1V1 = P2V2 where P1 = Pressure at a point prior to the booster P2 = Pressure at a point after the booster For almost every case, the volumetric rating of gas-fired equipment is in Btu/h, which can readily be converted to cfh. In the booster application, sizing criteria should be approached from a standard cfh (scfh) not an actual cfh (acfh) rating. Gas temperatures and density As stated, the temperature of the gas is usually constant. However, in the event that the gas is to be heated or cooled, the previously mentioned gas laws are affected by temperature. Gas density changes affect the constant but usually do not affect the relationship since the same mixture is boosted across the fan. High-rise building issues Consideration must be given to the rise effect in available gas pressure as gas rises in the piping through a high-rise building. Therefore, if the gas system supplies a kitchen on the first level and a boiler in the penthouse of a 50-story building, it may be necessary to boost the supply to the kitchen but not to the boiler. The gas rises to the penthouse through the piping system because of the density differential; its rising is dependent on this stack effect, which is directly related to the piping system layout. Design considerations Although a gas booster is a basic mechanical piece of equipment, there are significant design considerations that should be taken into account when applying it: 1. Indoor vs. outdoor location. This may be driven by local code or the end user. An indoor location involves a lower initial cost and lower costs for long-term maintenance. Outdoor locations are inherently safer. 2. Access. The location should be accessible for installation, inspection, and maintenance. The unit should not be so accessible as to create a security issue. Keep the equipment out of traffic patterns and protect it from heavy equipment. 3. Minimum and maximum flow rates. Boosters usually have a minimum flow rate that must be maintained so that the



booster’s motor is kept cool. When specifying a booster,

http://www.simpopdf.com always indicate the minimum flow required in addition to other design parameters. Cooling devices and bypass loops may be required if the application requires a turndown in flow (lowest flow expected) that is higher than the booster’s minimum flow. Controls and interlocking. Determine how the application should be controlled and what demands the application will put on the system. The control philosophy, method of electrically interlocking the system to the gas-fired equipment, and physical hardware will vary based on the application.

For some specific examples, see the schematics in Figure 2, which shows variations of a basic simplex booster system for an emergency generator. In Figure 2(A), the regulator controls maximum delivered pressure, and a combination high/low pressure switch on the tank cycles the booster to ensure emergency startup pressure within a design deadband for the generator. Oversized piping, in this case, can be substituted for the tank itself. Provide adequate volume so that the generator can fire and deliver standby power back to the booster system to continue operation during main power interrupt. In Figure 2(B), a dual booster system, the booster is controlled in a lead/lag control scenario. Should one booster fail, the second is started automatically. Unit operation is rotated automatically via the control panel to share the duty and to keep both units in operating order. The booster with a heat exchanger loop shown in Figure 2(C) has a potential of up to 15 psi (103.4 kPa) and down to 28 in. (711.2 mm) wc supply pressure. The system automatically diverts gas around the booster if there is sufficient supply pressure. While these illustrations obviously do not cover all the potential applications, they are provided to give the system designer some guidance. Sizing a gas booster A gas booster’s main purpose is to elevate the pressure of a volume of gas to overcome a supply pressure deficiency. When sizing a booster, an engineer needs to understand the following terms and issues: Maximum design flow (Qmax) The sum of all gas loads at the maximum capacity rating (MCR) for all equipment downstream of the booster that could possibly be required to operate simultaneously. Minimum design flow (Qmin) The minimum volumetric flow that could exist while the booster is operating. This flow is not always associated with the smallest Btu/h-rated piece of equipment. For example, when evaluating a 75,000,000 Btu/h (22 MW) boiler with a 10:1 turndown ratio in comparison to a 1.0 Btu/h (0.3 W) hot water heater that is on/off in operation, the larger Btu/h (W)-rated boiler has the smaller flow of 0.75 Btu/h (0.2 W) at its minimum firing rate. Turndown (TD) ratio The ratio of the MCR input to the equipment’s minimum, or low-fire, input. For example, a 100 Btu/h (29.3 W) burner that can fire at a minimum rate of 20 Btu/h (5.9 W) has a TD ratio of 5:1. Pressure droop and peak consumption Pressure droop is the inability of a supply system to maintain a steady or consistent inlet pressure as an increase in volumetric flow is demanded. Often, in areas where boosters are applied, the supply pressure in off-peak months when gas is not in such demand can be sufficient to run a system. As the local demand for gas increases, the supply system no longer can provide the gas efficiently and the pressure falls off or droops. It is the booster’s function to overcome the droop (or excessive pressure drop) of the supply system during such times. Flow rate relationships Do your flows for separate pieces of equipment relate to each other? In other words, do the three boilPSDMAGAZINE.ORG

ers always operate in unison while another process machine always 3. The allowable friction loss through the piping system. Simpo PDF Merge and Split Unregistered Version4. - http://www.simpopdf.com operates off peak and alone? Relationships among the equipment A piping layout that shows all the connected equipment, can significantly affect both maximum and minimum flow rates. allowing determination of the measured length of piping to Test block A factor of safety added to design criteria. Typically, the furthest connection. This, in turn, gives the equivalent a minimum of 5% added volume and 10% added static pressure length of piping. should be applied to the design criteria. When specifying the equip- 5. The maximum probable demand. ment, ensure that you note both the design and test block condi- 6. A pipe sizing method acceptable to the AHJ or local code. tions. This makes other people working on the system aware and The information needed by both the utility company and the ensures that safety factors are not applied to criteria that already engineer The following are intended to be complete lists of items. include safety factors. Not all items will be necessary for all projects. Minimum inlet pressure (PI-min) What is the minimum supply The following criteria and information shall be obtained in writpressure in in. (mm) wc gauge? This must be evaluated during peak ing from the public utility company and given to the engineer: flow demands both for the equipment and for the local area. Always 1. BTU content of the gas provided. evaluate during flow, not static, conditions. It is also important to 2. Minimum pressure of the gas at the outlet of the meter. know how high the inlet pressure is expected to rise during off-peak 3. Extent of the installation work done by the utility company periods. A booster is typically rated to about 5 psi (34.5 kPa). It may and the point of connection to the meter by the facility conbe possible to exceed this rating during off-peak demand periods; struction contractor. therefore, a bypass system or other means of protection is required. 4. The location of the utility supply main and the proposed run Often this pressure can be specified by the local gas company as the of pipe on the site by the utility company. This shall be in the minimum guaranteed gas pressure from their supply system. Also, form of a marked-up plan or description of the work. Include the maximum inlet pressure (PI-max) must be determined. the expected date of installation if no gas is available. Maximum outlet pressure (PO-max) List all maximum and 5. Acceptable location of the meter and /or regulator assembly required supply pressures for the various pieces of equipment being or a request to locate the meter at a particular location. supplied gas from the booster. Determine the differential between 6. Any work required by the owner to allow the meter assembly the highest expected gas pressure supply to the booster (e.g., 8 in. to be installed (such as a meter pit or slab on grade). [203.2 mm] wc) and the lowest maximum supply pressure rating 7. Types of gas service available and the cost of each. to a piece of equipment (e.g., 18 in. [457.2 mm] wc). The booster’s For the utility company to provide this data, the following inforpressure gain should not exceed this differential (for the above example, 18 – 8 = 10 in. [457.2 – 203.2 = 254 mm] wc) unless other mation must be provided to them: 1. The total connected load. The utility will use its own diversity means of protecting the downstream equipment are provided. factor to calculate the size of the service line. For the design Outlet pressure protection There are several ways to protect of the project’s interior piping, the design engineer will select equipment downstream of a booster should it be necessary due the diversity factor involved. to potential over-pressurization during off-peak periods. If all the equipment being serviced operates at nominally the same pressure, 2. Minimum pressure requirements for the most demanding device. install a regulator on the inlet or outlet of the booster to maintain a controlled maximum outlet pressure. If the equipment being ser- 3. Site plan indicating the location of the proposed building on the site and the specific area of the building where the proviced operates at various inlet pressures, it may be best to supply a posed NG service will enter the building. regulator for each piece of equipment. Most often, packaged equip4. Preferred location of the meter/regulator assembly ment is supplied with its own regulator. If this is the case, review the 5. Expected date of the start of construction. equipment regulator’s maximum inlet pressure. To perform an evaluation of system requirements, do the following: 6. Different requirements for pressure. 7. Two site plans, one to be marked up and returned to the engi1. Establish design Qmin and Qmax per the previously discussed neer. definitions while evaluating TD requirements. 8. If any equipment has pilot lights. 2. Establish PI-min and PI-max per the previously discussed defini9. The hours of operation for the different types of equipment. tions. 10. Future equipment and capacities, if any, known at this time. 3. Define maximum inlet pressure requirements to equipment (PI-eq). The pressure available after the meter shall be established in 4. Define piping pressure losses (PPL) from the gas booster locawriting from the utility at the start of the project. If boilers or other tion to each piece of equipment. major equipment is being used, the pressure requirements and the 5. Design flow rate (QD) = Qmin to Qmax, cfh (m3/h). flow rate for that equipment must be provided to the utility. 6. Design pressure boost (DP) = PI-eq + PPL – PI-min. The allowable friction loss through the entire piping system 7. Test block flow (QTB) = (1.05 × Qmin) to (1.05 × Qmax). shall be established by the engineer. This value depends on the 8. Test block pressure boost: 1.10 × DP = PI-eq + PPL – PI-min. pressure provided by the utility company. The most often selected value under average conditions is 0.3 in. (7.6 mm) wc, with a range where of 0.2–0.5 in. (5–13 mm) wc. The residential appliances (range and PPL = Pressure losses, psi (kPa) dryer) require a pressure of 3.5 in. (89 mm) wc. If the pressure from the utility company is around 7 in. (178 mm) wc, a higher friction Interior NG Pipe Sizing To accurately size all elements of the piping system, calculate or loss allowance could be used for economy in pipe sizing. If the pressure from the utility company is 4 in. (102 mm) wc, a 0.2 in. (5 obtain the following information: mm) wc is recommended. 1. The information needed by both the utility company and the A piping layout and the equivalent length of piping A piping engineer. layout is necessary to show the run of the whole piping system and 2. The gas pressure available after the meter assembly. JANUARY/FEBRUARY 2008


CONTINUING EDUCATION: Fuel Gas Piping Systems Table 5 Equivalent Lengths for Various Valve and Fitting Sizes

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Fitting

¾ (19.1)

1 (25.4) 1½ (38.1)

Pipe Size, in. (mm) 2 (50.8) 2½ (63.5)

3 (76.2)

4 (101.6)

Equivalent Lengths, ft (m) 2.00 (0.61) 2.50 (0.76) 3.00 (0.91) 4.00 (1.22) 5.50 (1.68) 6.50 (1.98)

90° elbow

1.00 (0.3)

Tee (run)

0.50 (0.15) 0.75 (0.23) 1.00 (0.3)

5 (127)

6 (152.4)

8 (203.2)

9.00 (2.74) 12.0 (3.66)

15.0 (4.57)

1.50 (0.46) 2.00 (0.61) 3.00 (0.91) 3.50 (1.07)

4.50 (1.37) 6.00 (1.83)

7.00 (2.13)

Tee (branch)

2.50 (0.76) 3.50 (1.07) 4.50 (1.37) 5.00 (1.52) 6.00 (1.83) 11.0 (3.35) 13.0 (3.96)

18.0 (5.49) 24.0 (7.32)

30.0 (9.14)

Gas cock (approx.)

4.00 (1.22) 5.00 (1.52) 7.50 (2.29) 9.00 (2.74) 12.0 (3.66) 17.0 (5.18) 20.0 (6.1)

28.0 (8.53) 37.0 (11.28) 46.0 (14.02)

Note: The pressure drop through valves should be taken from manufacturers’ published data rather than using the equivalent lengths, since the various patterns of gas cocks can vary greatly.

all the connected appliances and equipment. The equivalent length of piping is calculated by measuring the actual length of proposed piping from the meter to the furthest connection and then adding 50% of the measured length to find the equivalent length. If a very accurate determination of the equivalent length is necessary, it will be necessary to count the fittings and valves and then add those to the measured length. Refer to Table 5 for the equivalent amount of pipe to be added for various valves and fittings. It is common practice not to use the vertical length in either calculation because NG is lighter than air. It expands at the rate of 1 in. (25.4 mm) wc for each 15 ft of elevation as the gas rises. The increase in pressure due to the height will offset any friction loss in the piping. The maximum probable demand is calculated by the engineer with input from the owner if necessary. The primary usage of gas is for cooking and clothes drying at residences, for Bunsen burners or heating (boilers) in laboratories, or cooling equipment in industrial projects. For residential usage, Figure 3 for large residences

and Figure 4 for smaller projects give a direct reading of the usage in cfh (m3/hr). These direct reading tables give flow rate usage by using the number of apartments. Figure 5 is a riser diagram of multiple dwellings that gives the size of gas risers used for cooking and drying for both single and back-to-back installations. For laboratories, use Table 5 for the diversity factor. For schools, use no diversity factor for individual classrooms. Use no diversity factor for groups of classrooms if information of proposed usage is not conclusive or available from the owner. For industrial usage, a diversity factor generally is not used because of the possibility that all equipment may be in use at one time. For a listing of input requirements for common appliances, refer to Table 3.

NG Pipe Sizing Methods A number of formulas can be used to calculate the capacity of NG piping based on such variables as delivery pressure, pressure drop through the piping system, pipe size, pipe material, and length of piping. These formulas are referenced in numerous current model

Figure 3 Gas Demand for Multiple-unit Dwellings with More Than 50 Apartments



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codes as well as in NFPA 54. The most commonly referenced forof piping is not considered due to the pressure gained as the Merge Split Unregistered Version - http://www.simpopdf.com mulaSimpo for gas PDF pressures underand 1½ psi (10.3 kPa) is the Spitzglass gas rises. This very closely approximates the friction loss in the formula. The other commonly referenced equation for pressures of piping. 1½ psi (10.3 kPa) and more is the Weymouth formula. Using these 2. Select the column showing the distance that is equal to or formulas for sizing is a very cumbersome task, so they are rarely, if more than the equivalent length just calculated. ever, used. However, they were used as a basis for the sizing tables 3. Use the vertical column to locate all gas demand figures for that are included in this chapter and reproduced with permission this particular system. This is the only column to use. Startfrom the NFPA. These tables are regarded as the most conservaing at the most remote outlet, find in the vertical column the tive method for sizing NG pipe. Proprietary tables and calculators calculated gas demand for that design point. If the exact figure are available from various organizations and are considered more is not shown, choose the figure closest to or more than the accurate than those shown here. calculated demand. The tables are based on Schedule 40 steel pipe, cfh of gas, and a 4. Opposite this demand figure selected, in the column at the specific gravity of 0.60. The initial pressures are different, and the left, find the correct size of pipe. friction loss allowable is indicated. The following tables are pro- 5. Proceed for each design point and each section of pipe. For vided: each section of pipe, determine the total gas demand supplied Table 6 pressure less than 2 psi (14 kPa), loss of 0.3 in. (7.5 mm) by that section. wc If the gas used for the system has a different specific gravity than Table 7 pressure less than 2 psi (14 kPa), loss of 0.5 in. (12.5 mm) natural gas, obtain that figure from Table 12 and use this as a multiwc plier for the specific gas selected. Table 8 pressure of 5 psi (35 kPa), loss of 10 percent Table 9 pressure 10 psi (70 kPa), loss of 10 percent Table 10 pressure 20 psi (140 kPa), loss of 10 percent Figure 5 Gas Riser Pipe Sizing for Multiple Dwellings Table 11 pressure 50 psi (350 kPa), loss of 10 percent Note 1 cfh gas = 0.3 m3/hr To determine the size of each section of pipe in a gas supply system using the gas pipe sizing tables, the following method should be used: 1. Measure the length of the pipe from the gas meter location to the most remote outlet on the system. Add a fitting allowance of 50% of the measured length. This now gives you the equivalent length of pipe. For natural gas, the vertical portion

Figure 4 Gas Demand for Multiple-unit Dwellings with Less than 50 Apartments



CONTINUING EDUCATION: Fuel Gas Piping Systems Table 6 Pressure less than 2 psi (14 kPa), loss of 0.3 in. (7.5 mm) wc Pipe Size (in.) 1 3 Nominal ⁄2 ⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4 Actual ID 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026 Length (ft) Capacity in Cubic Feet of Gas per Hour 10 131 273 514 1,060 1,580 3,050 4,860 8,580 17,500 20 90 188 353 726 1,090 2,090 3,340 5,900 12,000 30 72 151 284 583 873 1,680 2,680 4,740 9,660 40 62 129 243 499 747 1,440 2,290 4,050 8,270 50 55 114 215 442 662 1,280 2,030 3,590 7,330 60 50 104 195 400 600 1,160 1,840 3,260 6,640 70 46 95 179 368 552 1,060 1,690 3,000 6,110 80 42 89 167 343 514 989 1,580 2,790 5,680 90 40 83 157 322 482 928 1,480 2,610 5,330 100 38 79 148 304 455 877 1,400 2,470 5,040 125 33 70 131 269 403 777 1,240 2,190 4,460 150 30 63 119 244 366 704 1,120 1,980 4,050 175 28 58 109 224 336 648 1,030 1,820 3,720 200 26 54 102 209 313 602 960 1,700 3,460 250 23 48 90 185 277 534 851 1,500 3,070 300 21 43 82 168 251 484 771 1,360 2,780 350 19 40 75 154 231 445 709 1,250 2,560 400 18 37 70 143 215 414 660 1,170 2,380 450 17 35 66 135 202 389 619 1,090 2,230 500 16 33 62 127 191 367 585 1,030 2,110 550 15 31 59 121 181 349 556 982 2,000 600 14 30 56 115 173 333 530 937 1,910 650 14 29 54 110 165 318 508 897 1,830 700 13 27 52 106 159 306 488 862 1,760 750 13 26 50 102 153 295 470 830 1,690 800 12 26 48 99 148 285 454 802 1,640 850 12 25 46 95 143 275 439 776 1,580 900 11 24 45 93 139 267 426 752 1,530 950 11 23 44 90 135 259 413 731 1,490 1,000 11 23 43 87 131 252 402 711 1,450 1,100 10 21 40 83 124 240 382 675 1,380 1,200 NA 20 39 79 119 229 364 644 1,310 1,300 NA 20 37 76 114 219 349 617 1,260 1,400 NA 19 35 73 109 210 335 592 1,210 1,500 NA 18 34 70 105 203 323 571 1,160 1,600 NA 18 33 68 102 196 312 551 1,120 1,700 NA 17 32 66 98 189 302 533 1,090 1,800 NA 16 31 64 95 184 293 517 1,050 1,900 NA 16 30 62 93 178 284 502 1,020 2,000 NA 16 29 60 90 173 276 488 1,000


To convert gas pressure to various designations, refer to Table 13.

LIQUEFIED PETROLEUM GAS Liquefied petroleum gas (LPG) is a refined NG developed mainly for use beyond the utilities’ gas mains, but it has proven to be competitive in areas not covered by mains in rural areas. It is chiefly a blend of propane and butane with traces of other hydrocarbons remaining from the various production methods. The exact blend is controlled by the LPG distributor to match the climatic conditions of the area served. For this reason, the engineer must confirm the heat value of the supplied gas. Unlike natural gas, 100 percent propane has a specific gravity of 1.53 and a rating of 2,500 Btu/cf (93 MJ/cm3).



5 5.047

6 6.065

8 7.981

10 12 10.020 11.938

31,700 21,800 17,500 15,000 13,300 12,000 11,100 10,300 9,650 9,110 8,080 7,320 6,730 6,260 5,550 5,030 4,630 4,310 4,040 3,820 3,620 3,460 3,310 3,180 3,060 2,960 2,860 2,780 2,700 2,620 2,490 2,380 2,280 2,190 2,110 2,030 1,970 1,910 1,850 1,800

51,300 105,000 191,000 303,000 35,300 72,400 132,000 208,000 28,300 58,200 106,000 167,000 24,200 49,800 90,400 143,000 21,500 44,100 80,100 127,000 19,500 40,000 72,600 115,000 17,900 36,800 66,800 106,000 16,700 34,200 62,100 98,400 15,600 32,100 58,300 92,300 14,800 30,300 55,100 87,200 13,100 26,900 48,800 77,300 11,900 24,300 44,200 70,000 10,900 22,400 40,700 64,400 10,100 20,800 37,900 59,900 8,990 18,500 33,500 53,100 8,150 16,700 30,400 48,100 7,490 15,400 28,000 44,300 6,970 14,300 26,000 41,200 6,540 13,400 24,400 38,600 6,180 12,700 23,100 36,500 5,870 12,100 21,900 34,700 5,600 11,500 20,900 33,100 5,360 11,000 20,000 31,700 5,150 10,600 19,200 30,400 4,960 10,200 18,500 29,300 4,790 9,840 17,900 28,300 4,640 9,530 17,300 27,400 4,500 9,240 16,800 26,600 4,370 8,970 16,300 25,800 4,250 8,720 15,800 25,100 4,030 8,290 15,100 23,800 3,850 7,910 14,400 22,700 3,680 7,570 13,700 21,800 3,540 7,270 13,200 20,900 3,410 7,010 12,700 20,100 3,290 6,770 12,300 19,500 3,190 6,550 11,900 18,800 3,090 6,350 11,500 18,300 3,000 6,170 11,200 17,700 2,920 6,000 10,900 17,200

Easy storage for relatively large quantities of energy has led to widespread acceptance and usage of LPG in all areas previously served by utilities providing NG to users, including automotive purposes. In addition, a principal use is for the heating of industrial projects. It does not take the place of NG but provides an alternative energy source when the owners want to use a low, interruptible rate for heating purposes. When used for this purpose, experience has shown that the mixing with air should produce a gas with the heating value of 1,500 Btu/cf (a specific gravity of 1.30) for ease of burning and ignition. Use Table 12 for the factor to be used for sizing.

Storage LPG storage tanks can be provided by the vendor or the customer and are subject to the regulations of the U.S. Department of Transportation (DOT) and the local authority, as well as NFPA standards, PSDMAGAZINE.ORG

Table 7 pressure less than 2 psi (14 kPa), loss of 0.5 in. (12.5 mm) wc Pipe Size (in.) 1 3 Nominal ⁄2 ⁄4 1 11⁄4 11⁄2 2 21⁄2 3 4 5 Actual ID 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026 5.047 Length (ft) Capacity in Cubic Feet of Gas per Hour 10 172 360 678 1,390 2,090 4,020 6,400 11,300 23,100 41,800 20 118 247 466 957 1,430 2,760 4,400 7,780 15,900 28,700 30 95 199 374 768 1150 2,220 3,530 6,250 12,700 23,000 40 81 170 320 657 985 1,900 3,020 5,350 10,900 19,700 50 72 151 284 583 873 1,680 2,680 4,740 9,660 17,500 60 65 137 257 528 791 1,520 2,430 4,290 8,760 15,800 70 60 126 237 486 728 1,400 2,230 3,950 8,050 14,600 80 56 117 220 452 677 1300 2,080 3,670 7,490 13,600 90 52 110 207 424 635 1220 1,950 3,450 7,030 12,700 100 50 104 195 400 600 1160 1,840 3,260 6,640 12,000 125 44 92 173 355 532 1020 1,630 2,890 5,890 10,600 150 40 83 157 322 482 928 1,480 2,610 5,330 9,650 175 37 77 144 296 443 854 1,360 2,410 4,910 8,880 200 34 71 134 275 412 794 1270 2,240 4,560 8,260 250 30 63 119 244 366 704 1120 1,980 4,050 7,320 300 27 57 108 221 331 638 1020 1,800 3,670 6,630 350 25 53 99 203 305 587 935 1,650 3,370 6,100 400 23 49 92 189 283 546 870 1,540 3,140 5,680 450 22 46 83 177 266 512 816 1,440 2,940 5,330 500 21 43 82 168 251 484 771 1,360 2,780 5,030 550 20 41 78 159 239 459 732 1290 2,640 4,780 600 19 39 74 152 228 438 699 1240 2,520 4,560 650 18 38 71 145 218 420 669 1180 2,410 4,360 700 17 36 68 140 209 403 643 1140 2,320 4,190 750 17 35 66 135 202 389 619 1090 2,230 4,040 800 16 34 63 130 195 375 598 1060 2,160 3,900 850 16 33 61 126 189 363 579 1020 2,090 3,780 900 15 32 59 122 183 352 561 992 2,020 3,660 950 15 31 58 118 178 342 545 963 1,960 3,550 1,000 14 30 56 115 173 333 530 937 1,910 3,460 1,100 14 28 53 109 164 316 503 890 1,810 3,280 1,200 13 27 51 104 156 301 480 849 1,730 3,130 1,300 12 26 49 100 150 289 460 813 1,660 3,000 1,400 12 25 47 96 144 277 442 781 1,590 2,880 1,500 11 24 45 93 139 267 426 752 1,530 2,780 1,600 11 23 44 89 134 258 411 727 1,480 2,680 1,700 11 22 42 86 130 250 398 703 1,430 2,590 1,800 10 22 41 84 126 242 386 682 1,390 2,520 1,900 10 21 40 81 122 235 375 662 1,350 2,440 2,000 NA 20 39 79 119 229 364 644 1,310 2,380


so the plumbing designer has little opportunity to design storage tanks and piping, per se. Normally, the designer starts at the storage supply outlet, and the piping system is generally in a low pressure range of 20 psig to 11 in wc.

6 6.065

8 7.981

67,600 46,500 37,300 31,900 28,300 25,600 23,600 22,000 20,600 19,500 17,200 15,600 14,400 13,400 11,900 10,700 9,880 9,190 8,620 8,150 7,740 7,380 7,070 6,790 6,540 6,320 6,110 5,930 5,760 5,600 5,320 5,070 4,860 4,670 4,500 4,340 4,200 4,070 3,960 3,850

139,000 95,500 76,700 65,600 58,200 52,700 48,500 45,100 42,300 40,000 35,400 32,100 29,500 27,500 24,300 22,100 20,300 18,900 17,700 16,700 15,900 15,200 14,500 14,000 13,400 13,000 12,600 12,200 11,800 11,500 10,900 10,400 9,980 9,590 9,240 8,920 8,630 8,370 8,130 7,910

10 12 10.020 11.938 252,000 173,000 139,000 119,000 106,000 95,700 88,100 81,900 76,900 72,600 64,300 58,300 53,600 49,900 44,200 40,100 36,900 34,300 32,200 30,400 28,900 27,500 26,400 25,300 24,400 23,600 22,800 22,100 21,500 20,900 19,800 18,900 18,100 17,400 16,800 16,200 15,700 15,200 14,800 14,400

399,000 275,000 220,000 189,000 167,000 152,000 13,900 130,000 122,000 115,000 102,000 92,300 84,900 79,000 70,000 63,400 58,400 54,300 50,900 48,100 45,700 43,600 41,800 40,100 38,600 37,300 36,100 35,000 34,000 33,100 31,400 30,000 28,700 27,600 26,600 25,600 24,800 24,100 23,400 22,700

suitable for site mains. The engineer shall obtain or request the pressure provided by the supplier and decide upon the pressure drop in the piping system that would be appropriate. The AHJ shall be consulted regarding acceptance of any pressure selected.

LPG SIZING

STORAGE TANKS

The pressure of LPG is set by the supplier or the engineer. If the piping is to be run on the site, the pressure would be set higher for economy of pipe sizing, and a regulator would be provided to lower the pressure to a value that would be compatible with equipment served. A lower pressure would be used within a building. Propane gas shall be sized in accordance with. Tables 14 and 15 that have been developed by the NFPA. Table 14 is based on an outlet pressure of 11 in. wc.(280 mm) that would be suitable for interior piping. Table 15 is based on a higher outlet pressure more

Small tanks (for example, those for residential cooking and heating) are allowed to be located in close proximity to buildings. Large tanks (e.g., for industrial or multiple building use), however, have strict requirements governing their locations in relation to buildings, public use areas, and property lines. If large leaks occur, the heavier-than-air gas will hug the ground and form a fog. The potential for a hazardous condition could exist. Proper safety precautions and equipment, as well as good judgment, must be utilized when



CONTINUING EDUCATION: Fuel Gas Piping Systems Table Simpo 8 Pressure of 5 psiMerge (35 kPa), loss of 10Split percentUnregistered Version - http://www.simpopdf.com PDF and Pipe Size of Total Equivalent Length of Pipe (ft) Schedule 40 Standard Internal Pipe (in.) Diameter (in.) 50 100 150 200 250 300 400 500 1000 1.00 1.049 1,989 1,367 1,098 940 833 755 646 572 393 1.25 1.380 4,084 2,807 2,254 1,929 1,710 1,549 1,326 1,175 808 1.50 1.610 6,120 4,206 3,378 2,891 2,562 2,321 1,987 1,761 1,210 2.00 2.067 11,786 8,101 6,505 5,567 4,934 4,471 3,827 3,391 2,331 2.50 2.469 18,785 12,911 10,368 8,874 7,865 7,126 6,099 5,405 3,715 3.00 3.068 33,209 22,824 18,329 15,687 13,903 12,597 10,782 9,559 6,568 3.50 3.548 48,623 33,418 26,836 22,968 20,356 18,444 15,786 13,991 9,616 4.00 4.026 67,736 46,555 37,385 31,997 28,358 25,694 21,991 19,490 13,396 5.00 5.047 122,544 84,224 67,635 57,887 51,304 46,485 39,785 35,261 24,235 6.00 6.065 198,427 136,378 109,516 93,732 83,073 75,270 64,421 57,095 39,241 8.00 7.981 407,692 280,204 225,014 192,583 170,683 154,651 132,361 117,309 80,626 10.00 10.020 740,477 508,926 408,686 349,782 310,005 280,887 240,403 213,065 146,438 12.00 11.938 1,172,269 805,694 647,001 553,749 490,777 444,680 380,588 337,309 231,830

1500 316 649 972 1,872 2,983 5,274 7,722 10,757 19,461 31,512 64,745 117,595 186,168

2000 270 555 832 1,602 2,553 4,514 6,609 9,207 16,656 26,970 55,414 100,646 159,336

Pressure 5.0 PSI (35 kPa) Pressure Drop of 10%

Table 9 Pressure 10 psi (70 kPa), loss of 10 percent Pipe Size of Schedule 40 Internal Standard Diameter Pipe (in.) (in.) 50 100 150 1.00 1.049 3,259 2,240 1,789 1.25 1.380 6,690 4,598 3,692 1.50 1.610 10,024 6,889 5,532 2.00 2.067 19,305 13,268 10,655 2.50 2.469 30,769 21,148 16,982 3.00 3.068 54,395 37,385 30,022 3.50 3.548 79,642 54,737 43,956 4.00 4.026 110,948 76,254 61,235 5.00 5.047 200,720 137,954 110,782 6.00 6.065 325,013 223,379 179,382 8.00 7.981 667,777 458,959 368,561 10.00 10.020 1,212,861 833,593 669,404 12.00 11.938 1,920,112 1,319,682 1,059,751

Total Equivalent Length of Pipe (ft) 200 1,539 3,160 4,735 9,119 14,535 25,695 37,621 52,409 94,815 153,527 315,440 572,924 907,010

250 1,364 2,801 4,197 8,082 12,882 22,773 33,343 46,449 84,033 136,068 279,569 507,772 803,866

300 1,236 2,538 3,802 7,323 11,672 20,634 30,211 42,086 76,140 123,288 253,310 460,078 728,361

400 500 1000 1500 2000 1,058 938 644 517 443 2,172 1,925 1,323 1,062 909 3,254 2,884 1,982 1,592 1,362 6,268 5,555 3,818 3,066 2,624 9,990 8,854 6,085 4,886 4,182 17,660 15,652 10,757 8,638 7,393 25,857 22,916 15,750 12,648 10,825 36,020 31,924 21,941 17,620 15,080 65,166 57,755 39,695 31,876 27,282 105,518 93,519 64,275 51,615 44,176 216,800 192,146 132,061 106,050 90,765 393,767 348,988 239,858 192,614 164,853 623,383 552,493 379,725 304,933 260,983


Table 10 Pressure 20 psi (140 kPa), loss of 10 percent Pipe Size of Total Equivalent Length of Pipe (ft) Schedule 40 Standard Internal Pipe (in.) Diameter (in.) 50 100 150 200 250 300 400 1.00 1.049 5,674 3,900 3,132 2,680 2,375 2,152 1,842 1.25 1.380 11,649 8,006 6,429 5,503 4,877 4,419 3,782 1.50 1.610 17,454 11,996 9,633 8,245 7,307 6,621 5,667 2.00 2.067 33,615 23,103 18,553 15,879 14,073 12,751 10,913 2.50 2.469 53,577 36,823 29,570 25,308 22,430 20,323 17,394 3.00 3.068 94,714 65,097 52,275 44,741 39,653 35,928 30,750 3.50 3.548 138,676 95,311 76,538 65,507 58,058 52,604 45,023 4.00 4.026 193,187 132,777 106,624 91,257 80,879 73,282 62,720 5.00 5.047 349,503 240,211 192,898 165,096 146,322 132,578 113,370 6.00 6.065 565,926 388,958 312,347 267,329 236,928 214,674 183,733 8.00 7.981 1,162,762 799,160 641,754 549,258 486,797 441,074 377,502 10.00 10.020 2,111,887 1,451,488 1,165,596 997,600 884,154 801,108 685,645 12.00 11.938 3,343,383 2,297,888 1,845,285 1,579,326 1,399,727 1,268,254 1,085,462

500 1,633 3,352 5,022 9,672 15,416 27,253 39,903 55,538 100,566 162,840 334,573 607,674 962,025

1000 1,122 2,304 3,452 6,648 10,595 18,731 27,425 38,205 69,118 111,919 229,950 417,651 661,194

1500 901 1,850 2,772 5,338 8,509 15,042 22,023 30,680 55,505 89,875 184,658 335,388 530,962

2000 771 1,583 2,372 4,569 7,282 12,874 18,849 26,258 47,505 76,921 158,043 287,049 454,435




PSDMAGAZINE.ORG

Table Simpo 11 Pressure 50 psiMerge (350 kPa),and loss of Split 10 percent PDF Unregistered Version - http://www.simpopdf.com Pipe Size of Total Equivalent Length of Pipe (ft) Schedule 40 Internal Standard Diameter Pipe (in.) (in.) 50 100 150 200 250 300 400 500 1000 1500 2000 1.00 1.049 12,993 8,930 7,171 6,138 5,440 4,929 4,218 3,739 2,570 2,063 1,766 1.25 1.380 26,676 18,335 14,723 12,601 11,168 10,119 8,661 7,676 5,276 4,236 3,626 1.50 1.610 39,970 27,471 22,060 18,881 16,733 15,162 12,976 11,501 7,904 6,348 5,433 2.00 2.067 76,977 52,906 42,485 36,362 32,227 29,200 24,991 22,149 15,223 12,225 10,463 2.50 2.469 122,690 84,324 67,715 57,955 51,365 46,540 39,832 35,303 24,263 19,484 16,676 3.00 3.068 216,893 149,070 119,708 102,455 90,804 82,275 70,417 62,409 42,893 34,445 29,480 3.50 3.548 317,564 218,260 175,271 150,009 132,950 120,463 103,100 91,376 62,802 50,432 43,164 4.00 4.026 442,393 304,054 244,166 208,975 185,211 167,814 143,627 127,294 87,489 70,256 60,130 5.00 5.047 800,352 550,077 441,732 378,065 335,072 303,600 259,842 230,293 158,279 127,104 108,784 6.00 6.065 1,295,955 890,703 715,266 612,175 542,559 491,598 420,744 372,898 256,291 205,810 176,147 8.00 7.981 2,662,693 1,830,054 1,469,598 1,257,785 1,114,752 1,010,046 864,469 766,163 526,579 422,862 361,915 10.00 10.020 4,836,161 3,323,866 2,669,182 2,284,474 2,024,687 1,834,514 1,570,106 1,391,556 956,409 768,030 657,334 12.00 11.938 7,656,252 5,262,099 4,225,651 3,616,611 3,205,335 2,904,266 2,485,676 2,203,009 1,514,115 1,215,888 1,040,643 Table 12 Specific Gravity Multipliers Specific Gravity 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70

Capacity Multiplier 1.310 1.230 1.160 1.100 1.040 1.000 0.962 0.926

Specific Gravity 0.75 0.80 0.85 0.90 1.00 1.10 1.20 1.30


Specific Gravity 1.40 1.50 1.60 1.70 1.80 1.90 2.00 2.10


Table 13 Conversion of Gas Prcssurc to Various Designations Equivalent Pressure per Equivalent Pressure per inches square inch inches square inch kP Water Mercury Pounds Ounces Water Mercury Pounds Ounces 0.002 0.01 0.007 0.0036 0.0577 8.0 0.588 0.289 4.62 0.05 0.20 0.015 0.0072 0.115 9.0 0.662 0.325 5.20 0.07 0.30 0.022 0.0108 0.173 0.10 0.40 0.029 0.0145 0.231 10.0 0.74 0.361 5.77 11.0 0.81 0.397 6.34 0.12 0.50 0.037 0.0181 0.239 12.0 0.88 0.433 0.15 0.60 0.044 0.0217 0.346 13.0 0.96 0.469 7.50 0.17 0.70 0.051 0.0253 0.404 0.19 0.80 0.059 0.0289 0.462 13.6 1.00 0.491 7.86 0.22 0.90 0.066 0.0325 0.520 13.9 1.02 0.500 8.00 14.0 1.06 0.505 8.08 0.25 1.00 0.074 0.036 0.577 0.3 1.36 0.100 0.049 0.785 15.0 1.10 0.542 8.7 0.4 1.74 0.128 0.067 1.00 16.0 1.18 0.578 9.2 0.5 2.00 0.147 0.072 1.15 17.0 1.25 0.614 9.8 0.72 2.77 0.203 0.100 1.60 18.0 1.33 0.650 10.4 0.76 3.00 0.221 0.109 1.73 19.0 1.40 0.686 10.9 1.0 4.00 0.294 0.144 2.31 20.0 1.47 0.722 11.5 1.2 5.0 0.368 0.181 2.89 0.903 14.4 1.5 6.0 0.442 0.217 3.46 25.0 1.84 0.975 15.7 1.7 7.0 0.515 0.253 4.04 27.2 2.00 1.00 16.0 27.7 2.03

locating large LPG storage tanks. The lines also have to be purged of air prior to the startup of the facility.

GLOSSARY

kP 2.0 2.2 2.5 2.7 3.0 3.2 3.37 3.4 3.5 3.7 4.0 4.2 4.5 4.7 5.0 6.2 6.7 6.9

Btu Abbreviation for British thermal unit, the quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Boiling point The temperature of a liquid at which the internal vapor pressure is equal to the external pressure exerted on the surface of the liquid. Burner A device for the final conveyance of gas, or a mixture of gas and air, to the combustion zone. Butane (C4H10) A saturated aliphatic hydrocarbon existing in two isomeric forms and used as a fuel and a chemical intermediate. Caloric value See heating value. Chimney A vertical shaft enclosing one or more flues for conveying flue gases to the outside atmosphere. Condensate The liquid that separates from a gas (including flue gas) due to a reduction in temperature. Cubic foot (meter) of gas The amount of gas that would occupy 1 cubic foot (cubic meter) when at a temperature of 60°F (15.6°C), saturated with water vapor, and under a pressure equivalent to that of 30 in. of mercury (101.3 kPa). Demand The maximum amount of gas per unit time, usually expressed in cubic feet per hour (liters per minute) or Btu (watts) per hour, required for the operation of the appliance(s) supplied. Dilution air Air that enters a draft hood or draft regulator and mixes with the flue gases. Diversity factor The ratio of the maximum probable demand to the maximum possible demand. Draft hood A device built into an appliance, or made a part of the vent connector from an appliance, that is designed to:



CONTINUING EDUCATION: Fuel Gas Piping Systems 1. Provide for the ready escape of the flue gases from the Table 14 100% Propane for Interior Piping Simpo PDFinMerge Version - http://www.simpopdf.com appliance the eventand of noSplit draft,Unregistered backdraft, or stoppage Nominal 1 3 Inside ⁄2 ⁄4 1 11⁄4 11⁄2 beyond the draft hood. 2. Prevent a backdraft from entering the appliance. 3. Neutralize the effect of stack action of the chimney or gas vent upon the operation of the appliance. Excess air Air that passes through the combustion chamber and the appliance flues in excess of that which is theoretically required for complete combustion. Flue gases The products of combustion plus the excess air in appliance flues or heat exchangers (before the draft hood or draft regulator). Fuel gas A gaseous compound used as fuel to generate heat. It may be known variously as utility gas, natural gas, liquefied peteroleum gas, propane, butane, methane, or a combination of the above. It has a caloric value that corresponds to the specific compound or combination of compounds. Care must be exercised in determining the caloric value for design purposes. Gas log An unvented, open-flame-type room heater consisting of a metal frame or base supporting simulated logs designed for installation in a fireplace. Gas train A series of devices pertaining to a fuel gas appliance located on the upstream side of the unit. Typically, it consists of a combination of devices and may include pipe, fittings, fuel, airsupervisory switches (e.g., pressure regulators), and safety shutoff valves. Gas-train vent A piped vent to atmosphere from a device on a gas train. Gas vents Factory-built vent piping and vent fittings listed by a nationally recognized testing agency, assembled and used in accordance with the terms of their listings, used for conveying flue gases to the outside atmosphere. 1. Type B gas vent. A gas vent for venting gas appliances with draft hoods and other gas appliances listed for use with type B gas vents. 2. Type B-W gas vent. A gas vent for venting listed gas-fired vented wall furnaces. 3. Type L vent. A gas vent for venting gas appliances listed for use with type L vents. Heating value (total) The number of British thermal units produced by the combustion, at constant pressure, of 1 cubic foot (cubic meter) of gas when the products of combustion are cooled to the initial temperature of the gas and air; the water vapor formed during combustion is condensed; and all the necessary corrections have been applied. LPG Liquefied petroleum gas, a mixture of propane and butane. Loads, connected The sum of the rated Btu input to individual gas utilization equipment connected to a piping system. May be expressed in cubic feet (cubic meters) per hour. Meter set assembly The piping and fittings installed by the serving gas supplier to connect the inlet side of the meter to the gas service and the outlet side of the meter to the customer’s building or yard piping. Pipe, equivalent length The resistance of valves, controls, and fittings to gas flow, expressed as equivalent length of straight pipe. Pressure drop The loss in static pressure due to friction or obstruction during flow through pipe, valves, fittings, regulators, and burners.



Actual Lenth (ft) 10 20 30 40 50 60 80 100 125 150 175 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 1,800 1,900 2,000

2 21⁄2 3 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 Capacity in Thousands of Btu per Hour 291 608 1,150 2,350 3,520 6,790 10,800 19,100 200 418 787 1,620 2,420 4,660 7,430 13,100 160 336 632 1,300 1,940 3,750 5,970 10,600 137 287 541 1,110 1,660 3,210 5,110 9,030 122 255 480 985 1,480 2,840 4,530 8,000 110 231 434 892 1,340 2,570 4,100 7,250 101 212 400 821 1,230 2,370 3,770 6,670 94 197 372 763 1,140 2,200 3,510 6,210 89 185 349 716 1,070 2,070 3,290 5,820 84 175 330 677 1,010 1,950 3,110 5,500 74 155 292 600 899 1,730 2,760 4,880 67 140 265 543 814 1,570 2,500 4,420 62 129 243 500 749 1,440 2,300 4,060 58 120 227 465 697 1,340 2,140 3,780 51 107 201 412 618 1,190 1,900 3,350 46 97 182 373 560 1,080 1,720 3,040 42 89 167 344 515 991 1,580 2,790 40 83 156 320 479 922 1,470 2,600 37 78 146 300 449 865 1,380 2,440 35 73 138 283 424 817 1,300 2,300 33 70 131 269 403 776 1,240 2,190 32 66 125 257 385 741 1,180 2,090 30 64 120 246 368 709 1,130 2,000 29 61 115 236 354 681 1,090 1,920 28 59 111 227 341 656 1,050 1,850 27 57 107 220 329 634 1,010 1,790 26 55 104 213 319 613 978 1,730 25 53 100 206 309 595 948 1,680 25 52 97 200 300 578 921 1,630 24 50 95 195 292 562 895 1,580 23 48 90 185 277 534 850 1,500 22 46 86 176 264 509 811 1,430 21 44 82 169 253 487 777 1,370 20 42 79 162 243 468 746 1,320 19 40 76 156 234 451 719 1,270 19 39 74 151 226 436 694 1,230 18 38 71 146 219 422 672 1,190 18 37 69 142 212 409 652 1,150

4 4.026 39,000 26,800 21,500 18,400 16,300 14,800 13,600 12,700 11,900 11,200 9,950 9,010 8,290 7,710 6,840 6,190 5,700 5,300 4,970 4,700 4,460 4,260 4,080 3,920 3,770 3,640 3,530 3,420 3,320 3,230 3,070 2,930 2,800 2,690 2,590 2,500 2,420 2,350

100% Propane, Pressure 11 in wc, Pressure Drop 0.5 in wc

Propane (C3H8) A gaseous hydrocarbon of the methane series, found in petroleum. Regulator, gas pressure A device for controlling and maintaining a uniform gas pressure. This pressure is always lower than the supply pressure at the inlet of the regulator. Safety shutoff device A device that is designed to shut off the gas supply to the controlled burner(s) or appliance(s) in the event that the source of ignition fails. This device may interrupt the flow of gas to the main burner(s) only or to the pilot(s) and main burner(s) under its supervision. Specific gravity The ratio of the weight of a given volume of gas to that of the same volume of air, both measured under the same conditions. Vent connector That portion of the venting system that connects the gas appliance to the gas vent, chimney, or single-wall metal pipe. Vent gases The products of combustion from a gas appliance plus the excess air and the dilution air in the venting system above the draft hood or draft regulator.

REFERENCES PSDMAGAZINE.ORG

Table 15 100% Propane for Site Mains Simpo PDF Merge and Split Unregistered Nominal 1 3 Inside ⁄2 ⁄4 1 11⁄4 11⁄2 2 21⁄2 Actual 0.622 0.824 1.049 1.380 1.610 2.067 2.469 Lenth (ft) Capacity in Thousands of Btu per Hour 10 5,890 12,300 23,200 47,600 71,300 137,000 219,000 20 4,050 8,460 15,900 32,700 49,000 94,400 150,000 30 3,250 6,790 12,800 26,300 39,400 75,800 121,000 40 2,780 5,810 11,000 22,500 33,700 64,900 103,000 50 2,460 5,150 9,710 19,900 29,900 57,500 91,600 60 2,230 4,670 8,790 18,100 27,100 52,100 83,000 70 2,050 4,300 8,090 16,600 24,900 47,900 76,400 80 1,910 4,000 7,530 15,500 23,200 44,600 71,100 90 1,790 3,750 7,060 14,500 21,700 41,800 66,700 100 1,690 3,540 6,670 13,700 20,500 39,500 63,000 125 1,500 3,140 5,910 12,100 18,200 35,000 55,800 150 1,360 2,840 5,360 11,000 16,500 31,700 50,600 175 1,250 2.620 4,930 10,100 15,200 29,200 46,500 200 1,160 2,430 4,580 9,410 14,100 27,200 43,300 250 1,030 2,160 4,060 8,340 12,500 24,100 38,400 300 935 1,950 3,680 7,560 11,300 21,800 34,800 350 860 1,800 3,390 6,950 10,400 20,100 32,000 400 800 1,670 3,150 6,470 9,690 18,700 29,800 450 751 1,570 2,960 6,070 9,090 17,500 27,900 500 709 1,480 2,790 5,730 8,590 16,500 26,400 550 673 1,410 2,650 5,450 8,160 15,700 25,000 600 642 1,340 2,530 5,200 7,780 15,000 23,900 650 615 1,290 2,420 4,980 7,450 14,400 22,900 700 591 1,240 2,330 4,780 7,160 13,800 22,000 750 569 1,190 2,240 4,600 6,900 13,300 21,200 800 550 1,50 2,170 4,450 6,660 12,800 20,500 850 532 1,110 2,100 4,300 6,450 12,400 19,800 900 516 1,080 2,030 4,170 6,250 12,000 19,200 950 501 1,050 1,970 4,050 6,070 11,700 18,600 1,000 487 1,020 1,920 3,940 5,900 11,400 18,100 1,100 463 968 1,820 3,740 5,610 10,800 17,200 1,200 442 923 1,740 3,570 5,350 10,300 16,400 1,300 423 884 1,670 3,420 5,120 9,870 15,700 1,400 406 849 1,600 3,280 4,920 9,480 15,100 1,500 391 818 1,540 3,160 4,740 9,130 14,600 1,600 378 790 1,490 3,060 4,580 8,820 14,100 1,700 366 765 1,440 2,960 4,430 8,530 13,600 1,800 355 741 1,400 2,870 4,300 8,270 13,200 1,900 344 720 1,360 2,780 4,170 8,040 12,800 2,000 335 700 1,320 2,710 4,060 7,820 12,500

10. National Fire Protection Association. Oxygen-fuel gas

Version - http://www.simpopdf.com systems for weldings and cuttings. NFPA 51. Boston. 3 3.068

4 4.026

387,000 266,000 214,000 183,000 162,000 147,000 135,000 126,000 118,000 111,000 98,700 89,400 82,300 76,500 67,800 61,500 56,500 52,600 49,400 46,600 44,300 42,200 40,500 38,900 37,400 36,200 35,000 33,900 32,900 32,000 30,400 29,000 27,800 26,700 25,700 24,800 24,000 23,300 22,600 22,000

789,000 543,000 436,000 373,000 330,000 299,000 275,000 256,000 240,000 227,000 201,000 182,000 167,800 156,100 138,400 125,400 115,300 107,300 100,700 95,100 90,300 86,200 82,500 79,300 76,400 73,700 71,400 69,200 67,200 65,400 62,100 59,200 56,700 54,500 52,500 50,700 49,000 47,600 46,200 44,900

11. National Fire Protection Association. Powered industrial trucks. NFPA 505. Boston. 12. U.S. Army Corps of Engineers manual. EM-1110-34-166. 13. Frankel, M., Facility Piping Systems Handbook, 2002, McGraw Hill, New York City The material reproduced from the NFPA is not the official and complete position of the NFPA on the referenced subject which is presented only by the standard in its entirety.

100% Propane Pressure 10 PSI (70 kPa) Pressure Loss 3.0 PSI (21 kPa)

1. American Society of Heating, Refrigerating and Air Conditioning Engineers. Handbooks. Fundamentals and Equipment Vols. Latest ed. New York. 2. American Society of Mechanical Engineers (ASME). Fuel gas piping. ASME B31.2. 3. Ingersoll-Rand Company. 1969. Compressed air and gas data. New York. 4. International Association of Plumbing and Mechanical Officials (IAPMO) Code. 5. n.a. 1994. Mechanical engineering reference manual. 9th ed. Professional Publications. 6. Mohinder Nayer ed, . 1998. Piping handbook. New York: McGraw-Hill. 7. National Fire Protection Association. Cutting and welding processes. NFPA 51B. Boston, Mass. 8. National Fire Protection Association (NFPA). LP-gases at utility gas plants. NFPA 59. Boston Mass. 9. National Fire Protection Association. National fuel gas code. NFPA 54. Boston, Mass. JANUARY/FEBRUARY 2008


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Continuing Education from Plumbing Systems & Design Diane M. Wingard, CPD

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The technical article you must read to complete the exam is located at www.psdmagazine.org. Just click on “Plumbing Systems & Design Continuing Education Article and Exam” at the top of the page. The following exam and application form also may be downloaded from the website. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward CPD renewal or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

About This Issue’s Article The January/February 2008 continuing education article is “Fuel Gas Piping Systems,” Chapter 7 of Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems. This chapter describes fuel gas systems on consumer sites from the property line to the final connection with the most remote gas appliance or piece of equipment. The system is intended to provide sufficient pressure and volume for all uses. Since natural gas (NG) is a nonrenewable energy resource, the engineer should design for its efficient use. The direct utilization of NG is preferable to the use of electrical energy when electricity is obtained from the combustion of gas or oil. However, in many areas, the gas supplier and/or governmental agencies may impose regulations that restrict the use of natural gas. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Fuel Gas Piping Systems” (PSD 144)

PSD 144


1. The maximum allowable operating pressure for NG piping inside a building is ______. a. 0.5 psig b. determined by the authority having jurisdiction c. 5.0 psig d. no limit

7. LPG ______. a. needs to be alarmed when installed in crawl spaces b. is heavier than air c. vents shall be terminated a minimum of 3 feet horizontally from an opening d. slope on grade at the site

2. Which of the following is true when installing a pressure regulator? a. If located indoors, a relief vent may be required. b. It is provided to reduce the pressure of the incoming service to a safe operating pressure at the appliance. c. It normally is located outside before the meter. d. All of the above are true.

8. The purpose of a gas booster is ______. a. to increase the volumetric supply b. to increase the pressure c. to maintain the pressure delivered by the supplier d. none of the above

3. NG systems should be designed with an allowable pressure drop of ______. a. 0.2–0.5 inch w.c. b. 5.0 inches w.c. c. 10 psi d. none of the above 4. Which of the following is an acceptable material for fuel gas piping? a. black steel b. type L copper c. corrugated stainless steel tubing d. all of the above 5. LP gas can be stored in tanks at a pressure of ______. a. 300 psi, b. 150 psi, c. 250 psi, d. 1,000 psi 6. Which of the following is true for a fuel gas system? a. The flow rate of an appliance is equal to the consumption divided by 1,000. b. Natural gas is stored on site in large tanks. c. Gas systems always should be vented. d. Gas that is vented through regulators can always discharge into occupied space.



9. When providing a booster, ______. a. it is important to provide a regulator to protect the appliances from high pressure during times of low demand b. the equipment needs to be shut down during low demand periods c. it needs to be located outside of the building d. it is sized and provided by the gas supplier 10. Which of the following is required to size a system? a. allowable friction loss b. pipe layout c. probable demand d. all of the above 11. Which standard is referenced for fuel gas systems? a. NFPA 99 b. NFPA 101 c. NFPA 54 d. NFPA 13 12. Large LPG tanks must be located ______. a. away from the building in case of leaks b. near the appliances being served c. inside the building in a fire-rated enclosure d. underground

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Fuel Gas Piping Systems (PSD 144)

Appraisal Questions

Questions appear on page 18. Circle the answer to each question.

Q 1. Q 2. Q 3. Q 4. Q 5. Q 6. Q 7. Q 8. Q 9. Q 10. Q 11. Q 12.

A A A A A A A A A A A A

B B B B B B B B B B B B

C C C C C C C C C C C C

D D D D D D D D D D D D

1. 2. 3. 4. 5. 6.

Fuel Gas Piping Systems (PSD 144) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________




PSD 132

Plumbing Design for Health Care Facilities


MARCH/APRIL 2006

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Plumbing Design for Health Care Facilities


Introduction Health-care facilities, nursing homes, medical schools, and medical laboratories require plumbing systems that are more complex than those for most other types of building. The plumbing designer should work closely with the architect and facility staff and be involved in meetings and discussions in order to fully understand the plumbing requirements for any new or special medical equipment. The plumbing design must be coordinated with the civil, architectural, structural, mechanical, and electrical designs to ensure that adequate provisions have been made for utility capacities, for the necessary clearances and space requirements of the piping systems and related plumbing equipment, and for compliance with applicable codes. Health-care facilities may have different requirements or be exempt from some codes and standards, such as water and energy conservation codes and regulations regarding the physically challenged. The plumbing engineer should consult with the administrative authority in order to ensure conformance with local ordinances. This chapter discusses the provisions that may be encountered by the plumbing professional in the design of a health-care facility, including the following: plumbing fixtures and related equipment, the sanitary drainage system, the water-supply sys tem, laboratory waste and vent systems, pure-water systems, and medical-gas systems.

Plumbing Fixtures and Related Equipment Selection Process Meetings of the plumbing engineer with the architect and the facility staff to discuss the general and specific requirements regarding the plumbing fixtures and related equipment are usually held after the architect has prepared the preliminary drawings. At these meetings, the plumbing designer should assist in the selection of plumbing fixtures. Following these sessions, the plumbing designer can prepare the preliminary drawings and coordinate with the architect and facility staff the required piping systems and the plumbing fixture space requirements. In detailing the piping system spaces and plumbing fixture locations, the plumbing engineer should refer to the framing drawings. It is common for the architect to locate the piping shafts and the spaces in direct conflict with the framing; it is the plumbing designer’s responsibility to give the architect directions regarding the space requirements, fixture arrangement, and pipe-shaft size and locations. Following the meetings held with the architect and hospital staff, and with the preliminary drawings available, the plumbing designer should prepare an outline specification for the plumbing fixtures and related equipment. A guide to the required

plumbing fixtures and equipment for health-care facilities is provided in Table 1 and is discussed later in this section. A review of applicable code requirements regarding the quality and types of plumbing fixtures is always required. In addition to the local codes, it is necessary for the plumbing engineer to refer to the special hospital code requirements published by the local hospital authorities, the state hospital or health-department authorities, the Joint Commission for the Accreditation of Hospitals Organization (JCAHO), and the US Department of Health and Human Services. The architect may investigate these special requirements; however, the plumbing designer must be familiar with them since they contain many other applicable requirements (in addition to the table indicating the plumbing fixtures necessary for a particular installation). General Requirements Plumbing fixtures in health-care facilities should be of dense, impervious materials having smooth surfaces. Plumbing fixtures of vitreous china, enameled cast iron, and stainless steel are commonly used. Fixture brass—including faucets, traps, strain ers, escutcheons, stops, and supplies—should be chromium plated in a manner approved by the administrative authority. Die-cast metals should not be used. Faucets should have a laminar flow device (no alternative) of brass, Monel metal, or stainless-steel trim. Each plumbing fixture in health-care facilities should be provided with individual stop valves. Each water-service main, branch main, and riser shall have valves. Access shall be provided at all valves. All submerged inlets, faucets with hose adapters, and flush valves must be equipped with approved vacuum breakers. Backflow-prevention devices shall be installed on hose bibbs, supply nozzles used for the connection of hoses or tubing, and at other locations where the potable water supply must be protected from contamination. All plumbing fixtures, faucets, piping, solder, and fluxes used in potential drinking-water areas should comply with the latest maximum lead content regulations. Facilities for the physically challenged shall be in compliance with the Americans with Disabilities Act (ADA) accessibility guidelines. Fixtures for Specific Health-Care Areas General-use staff and public areas Water closets Vitreous china, siphon-jet water closet with elongated bowl design with open-front seat, less cover, should be specified. Wall-hung water closets are preferred for easy cleaning; however, floor-set models are also acceptable by most local jurisdictions. All water closets should be operated by watersaver flush valves. Lavatories and sinks Vitreous china, enameled cast iron or stainless-steel lavatories and sinks should be specified. The most commonly specified size is 20 × 18 × 7½ in. deep (508 × 457.2 × 190.5 mm deep). Hands-free controls (foot or knee

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 2: “Plumbing Design for Health Care Facilities.” ©2000, American Society of Plumbing Engineers. 56 Plumbing Systems & Design

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controls) are generally employed for staff use and for scrub-up sinks. In public areas, codes should be checked for the requirement of self-closing valves and/or metered valves. Stops should be provided for all supply lines. Aerators are not permitted; use laminar flow devices. Insulated and/or offset p-traps should be used for handicapped fixtures. Faucets Valves should be operable without hands, i.e., with wrist blades or foot controls or electronically. If wrist blades are used, blade handles used by the medical and nursing staff, patients, and food handlers shall not exceed 4½ in. (11.43 cm) in length. Handles on scrub sinks and clinical sinks shall be at least 6 in. (15.24 cm) long. Water spigots used in lavatories and sinks shall have clearances adequate to avoid contaminating utensils and the contents of carafes, etc.

Infant Bathtub

Glass Washer

Immersion Bath

Arm / Leg Bath

Ice Maker

Waste Grinder

Bedpan Washer

Sitz Bath

Bathtub / Shower

Emergency Eyewash

Emergency Shower

Floor Drain, Flushing Rim

Floor Drain

Cup Sink

Plaster Sink, Plaster Trap

Sink, Triple Compartment

Utility Sink

Scrub-up Sink

Clinic Sink, Flushing Rim

Counter Sink, Single Compartment Counter Sink, Double Compartment

Mop Service Basin

Drinking Fountain / Water Cooler

Shower

Handwashing Lavatory

Urinal

Elongated Water Closet, FlushValve

Table 1 Recommended Plumbing Fixtures and Related Equipment Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Medical-Care Areas l l l l l l l Public/Staff Restrooms l l l l l l Staff Lounge l l l l Patient Rooms l l l l Isolation Rooms l Nurse Stations l l Nursery l l l Formula Room l l l Intensive-Care Room l l l l Outpatient-Services Area l l l l l Emergency Rooms l l l Exam/Treatment Room l l l Labor Room l l l Janitor’s Closet l Clean Linen Holding l l Soiled Linen Holding l l l Nourishment Station l l l l l Patient Bathing Area l l l l l Critical-Care Area l Pharmacy l Surgical Scrub-up l Anesthesia Workroom l Surgical Supply Services l Surgical Cleanup Room l l l l Doctors’ Locker Room l l l Nurses’ Locker Room l l l Recovery Room l l Fracture Room l l l l Cleanup/Utility Room l Sub-Sterilizing Room l l l l l l l l l l l Medical Laboratory l l l l l l l Physical Therapy Room l l l l l l Cystoscopic Room l l l l l l l l Autopsy Room l l l l l l l l l l Dietary Services l l l l Laundry Facility l l l Family Waiting Room

Urinals Vitreous china wall-hung urinals with flush valves. Flush valves should be equipped with stops and may be of the exposed or concealed design. Showers The shower enclosures and floor specified by the plumbing engineer may be constructed of masonry and tile or of prefabricated fiberglass. Showers and tubs shall have nonslip walking surfaces. The shower valve should automatically compensate for variations in the water-supply pressure and temperature to deliver the discharge water at a set temperature that will prevent scaldings. Drinking fountains and water coolers Drinking fountains are available in vitreous china, steel and stainless steel. Units for exterior installations are available in suitable materials. Refrigerated water coolers are available in steel or stainless steel. All of these materials are acceptable by most local administrative

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CONTINUING EDUCATION: Plumbing Design for Health Care Facilities a uthorities. These units may be of the surface-mounted, semiA water closet and lavatory, with a fixed or fold-away water Simpo PDF Merge and Split Unregistered Versioncloset - http://www.simpopdf.com recessed or fully-recessed design. made of stainless steel, may be considered. This concept, Chilled water for drinking purposes should be provided as well as the construction of the unit, must be accepted by the between 45 and 50°F (7.2 and 10.0°C) and obtained by chill- administrative authority. ing water with a refrigeration compressor. The compressor may Ward rooms Ward rooms are infrequently found in healthbe enclosed in a cabinet with the dispenser (water cooler), care facilities, particularly in the private hospital field. These installed in a wall cavity behind a grill adjacent to the dispenser, rooms require at least 1 lavatory. This lavatory should be a minior remotely located for single or multiple dispensers. A remotely mum 20 × 18 in. (508 × 457.2 mm) and made of vitreous china installed unit for multiple dispensers (central system) should or stainless steel. The faucet should be of the gooseneck-spout have a recirculation system. design and provided with wrist-blade handles or hands-free Mop-service basins Floor-mounted mop-service basins controls. can be obtained in precast or (terazzo) molded-stone units of Nurseries The hospital’s nursery is usually provided with a various sizes. The plumbing engineer should specify the most minimum size 20 × 18 in. (508 × 457.2 mm) lavatory with handssuitable model. Rim guards are normally provided to protect the free controls and a high gooseneck spout. An infant’s bathtub, rims from damage and wall guards are provided to protect walls wall- or counter-mounted with an integral large drainboard and from splashing and chemical stains. The water-supply fixture is rinsing basin, is provided. Water-supply fittings are filler spouts usually a two-handle mixing faucet mounted on the wall with a over the basins with separate hand-valve controls. The spout wall brace, vacuum breaker, and hose adapter. and the spray are usually supplied and controlled through a Floor drains Floor drains in toilet rooms are optional in most thermostatic mixing valve. The ultimate in maintaining a safe cases; however, there are many instances where the floor drains water temperature is a separate supply tank. are required by the applicable codes. The plumbing designer Intensive-care rooms These rooms usually have utility sinks should give consideration to maintaining a trap seal in the floor with hands-free controls with high gooseneck spouts. A waterdrain through the use of deep-seal p-traps and/or trap prim- supply fitting equipped with a gooseneck spout and provision for ers. Floor drains shall not be installed in operating and delivery bedpan washing (either at an immediately adjacent water closet rooms. or at a separate bedpan washing station within an enclosure in Patient rooms These rooms (private or semiprivate) usually the room) should be provided. Newer designs have included are provided with a toilet room containing a water closet, a lava- combination lavatory/water closets for patient use, especially in tory, and a shower or bathtub. (Some hospitals use common cardiac-care units. shower and bath facilities for a group of patient rooms.) The Emergency (triage) rooms The plumbing fixtures provided plumbing fixtures should conform with the following recom in emergency rooms include a utility sink with an integral tray mendations: and a water-supply fitting with a gooseneck spout and wristThe water closet should be vitreous china, wall-hung or floor- blade handles. A vitreous china clinic sink (or a flushing-rim mounted design, with an elongated bowl. All water closets should sink), for the disposal of solids, with the water-supply fitting be operated by a flush valve. Water closets should have open- consisting of a flush valve and a separate combination faucet front seats, less cover. Bedpan lugs and bedpan washers are often with vacuum breaker mounted on the wall above the plumbing required by the local codes. Bedpan-flushing devices shall be fixture, should also be provided. provided in each inpatient toilet room; however, installation is Examination and treatment rooms These rooms are usuoptional in psychiatric and alcohol-abuse units, where patients ally provided with vitreous china or stainless-steel lavatories. are ambulatory. The water-supply fitting should be a hands-free valve equipped The lavatory should be a minimum of 20 × 18 × 7½ in. (508 × with a high, rigid, gooseneck spout. For a particular examina457.2 × 190.5 mm) deep. Lavatories should be installed at least 34 tion room or a group of patient rooms, an adjacent toilet room is in. (863.6 mm) above the floor. Mixing faucets should be of the provided containing a specimen-type water closet for inserting gooseneck-spout design and provided with wrist-blade handles, a specimen-collecting bedpan. The toilet room also requires a electronic, or hands-free controls. lavatory and a water supply with wrist-blade handles or handsThe shower is usually constructed of masonry and tile, acrylics, free controls and with a gooseneck spout. or fiberglass. The shower bases should be nonslip surfaces. The Physical-therapy treatment rooms The plumbing fixtures shower valve should automatically compensate for variations in and related equipment for these rooms usually include hydrothe water-supply pressure and temperature to deliver the dis- therapy immersion baths and leg, hip, and arm baths. These units charge water at a set temperature that will prevent scalding. Grab are generally furnished with electric-motor-driven whirlpool bars, located within the shower enclosure, are usually required by equipment. The water is introduced into the stainless-steel tank the local codes. The plumbing engineer should always check with enclosure by means of a thermostatic control valve to prevent the local administrative authority regarding approved designs. scalding, usually wall mounted adjacent to the bath for opera Bathtubs can be constructed of cast iron, fiberglass, acryl- tion by a hospital attendant. The water supply should be sized ics, or steel. Faucets should be as they are for showers. Shower to minimize tub fill time. The immersion baths are usually proheads may be of the stationary design, but in many locations vided with overhead hoists and canvas slings for facilitating the hand-held showers are required. lifting in and out of the bath of a completely immobile patient. A lavatory intended for use by doctors, nurses, and other hos- A hydrotherapy shower is sometimes required. These showers pital staff is sometimes required by the local ordinances. This usually consist of multiple shower heads, sometimes as many particular lavatory is usually located on the wall near the door as 12 to 16, vertically mounted in order to direct the streams of with a gooseneck spout and hands-free controls. water at a standing patient by means of a sophisticated control console operated by a hospital attendant. 58 Plumbing Systems & Design

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Cystoscopic rooms Among the various plumbing fixtures breaker. A bedpan washer should also be installed next to the Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com required in cystoscopic rooms are the following: wall-mounted clinical sink. The type of bedpan washer will depend upon the clinic sinks equipped with flush valves and bedpan washer and hospital’s method of washing and sterilizing bedpans. combination faucets; lavatories provided with water-supply fitBirthing rooms Each birthing room should include a vitreous tings and gooseneck spouts; and, in a separate adjacent room, china lavatory provided with a gooseneck spout and wrist-blade specimen water closet and a lavatory. If a floor drain is installed handles or hands-free controls. Each labor room should have in cystoscopy, it shall contain a nonsplash, horizontal-flow access to a water closet and a lavatory. A shower should be proflushing bowl beneath the drain plate. vided for the labor-room patients. The shower controls, includAutopsy room The autopsy room table is usually provided ing pressure/thermostatic mixing valve, should be located outwith cold and hot-water supplies, with a vacuum breaker or side the wet area for use by the hospital’s nursing staff. A water backflow preventer, and a waste line. It is necessary that the closet should be accessible to the shower facility. plumbing designer consult with the table manufacturer and Anesthesia workrooms This area is designed for the cleanthe administrative authority regarding the requirements of the ing, testing, and storing of the anesthesia equipment and should autopsy room table. Drain systems for autopsy tables shall be contain a work counter-mounted sink. The sink is usually made designed to positively avoid splatter or overflow onto floors or of stainless steel. The faucet should be of the gooseneck spout back siphonage and for easy cleaning and trap flushing. The design with wrist-blade handles and/or hands-free controls. autopsy room is also usually equipped with a stainless steel or Fracture rooms A large-size, vitreous china plaster, work vitreous china sink with hands-free fittings, a clinic sink and a sink equipped with a combination water-supply fitting and “blood” type floor drain. Adjacent to the autopsy room a water wrist-blade handles, gooseneck spout, and plaster trap on the closet and a shower room are usually provided. Many autopsy waste line (located for convenient access) should be provided. rooms are equipped with waste-disposal units integral with the Kitchens and Laundries sink. The plumbing designer should consult with the architect and the Nourishment stations These stations are usually provided on food-service consultant for kitchen equipment utility requireeach patient room floor near the nurse station for serving nour ments. Typically, one of these people should provide location ishment between regularly scheduled meals. A sink, equipped and rough-in drawings for all kitchen equipment. Normally for hand washing with hands-free controls, an icemaker, and a required are toilet fixtures for kitchen staff, food preparation hot-water dispenser (optional) to provide for the patient’s ser- sinks, hand-wash sinks, pot and pan-wash sinks, dishwashers, vice and treatment should be provided. glassware washers, floor drains, hose bibbs, mixing stations, Pharmacy and drug rooms The plumbing fixtures for these and grease interceptors. Kitchen grease traps shall be located rooms include medicine and solution sinks. These units can be and arranged to permit easy access without the necessity of counter-type or made of stainless steel or vitreous china with a entering food preparation or storage areas. Grease traps shall be mixing faucet and a swing spout. A solids interceptor should be of the capacity required and shall be accessible from outside the considered for compounding areas. building without the necessity of interrupting any services. In Operating-room areas No plumbing fixtures or floor drains dietary areas, floor drains and/or floor sinks shall be of a type are required in the hospital’s operating room. However, the that can be easily cleaned by the removal of a cover. Provide scrubbing station located adjacent to the operating room should floor drains or floor sinks at all “wet” equipment (such as ice have at least two scrub sinks, usually made of vitreous china or machines) and as required for the wet cleaning of floors. The stainless steel, furnished with hands-free water-supply fittings, location of floor drains and floor sinks shall be coordinated to and equipped with gooseneck spouts. These sinks should be avoid conditions where the location of equipment makes the large and deep enough to allow scrubbing of hands and arms to removal of covers for cleaning difficult. Also, the kitchen equipthe elbow. A soiled workroom, designed for the exclusive use of ment may require other utility services, such as fuel gas, steam, the hospital’s surgical staff, should be located near the operat- and condensate. ing room area. This workroom should contain a vitreous china, When considering laundry facilities, the plumbing designer flushing-rim clinical sink, for the disposal of solids, with the should consult with the architect and the laundry consultant for water-supply fittings consisting of a flush-valve bedpan washer equipment utility requirements. These facilities require largeand a separate faucet mounted on the wall above the fixture and capacity washers/extractors and dryers, presses, and folding hand-washing facilities consisting of a vitreous china or stain- machines. Waste-water drainage may require lint intercepters. less-steel lavatory with a gooseneck spout and equipped with These facilities are prime candidates for heat and water-recovwrist-blade handles. Substerile rooms should be equipped with ery systems. Also, the laundry equipment may require other an instrument sterilizer and general-purpose sink. The plumbing utility services, such as fuel gas, steam, and condensate. designer should consult with the instrument sterilizer manufacThe hot-water temperatures required for these areas (100, turer for any special requirements for the equipment. The gen- 140, and 180°F [38, 60, and 82°C]) are discussed in Data Book, eral-purpose sink can be countertop-mounted and equipped Volume 2, Chapter 6, “Domestic Water-Heating Systems.” with a hands-free water-supply fitting with a gooseneck spout. Recovery rooms The rooms for the post-anesthesia recovery Laboratory Rooms of surgical patients should include a hand-washing facility, such Laboratory sinks Most of the time architects provide the counas a vitreous china or stainless-steel lavatory equipped with a tertops and sinks, usually made of epoxy or other acid-resistant gooseneck spout and wrist-blade handles; and a vitreous china, materials, in their specifications. However, occasionally the flushing-rim, clinical sink for the disposal of solids, with the plumbing designer is responsible for selecting the laboratory water-supply fitting consisting of a flush valve and a separate sinks. Laboratory sinks should be acid resistant and can be of faucet mounted on the wall above the fixture with a vacuum stainless steel, stone, or plastic. Laboratory and cup sinks are MARCH/APRIL 2006


CONTINUING EDUCATION: Plumbing Design for Health Care Facilities currently available in epoxy resin, composition stone, natural face and body-spray units. The latest edition of the ANSI stanSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com stone, ceramic or vitreous china, polyester fiberglass, plastic, dard for emergency eyewash and shower equipment and local stainless steel, and lead. The lead type is not recommended codes should be consulted. A tempered water supply should be where mercury, nitric, hydrochloric or acetic acids are used. considered. Often these laboratory sinks are furnished with the laboratory Laboratory service outlets for gas, air, nitrogen, vacuum, and equipment as rectangular sinks or cup sinks mounted in, or other required gas services may be furnished as part of the related as part of, counter tops and as cup sinks in fume hoods. Rules equipment under another contract or may be included in the of thumb that can be used when the sink sizes are not recom- plumbing work. In either case, the plumbing designer should mended by the laboratory staff are as follows: be knowledgeable about the various types of service outlet cur rently available, the materials (or construction), and the usage 1. Sinks with a compartment size of 12 × 16 × 7.5 in. (304.8 × (diversity). It is desirable to have bodies of cast red brass, brass 406.4 × 190.5 mm) for general laboratory work areas. forgings, or brass bar stock that are specially designed for labo 2. Sinks with a compartment size of 18 × 24 × 10 in. (457.2 × ratory use and, where possible, made by one manufacturer. 609.6 × 254 mm) for classroom work and tests. Handles should be made of forged brass and provided with 3. Sinks with a compartment size of 24 × 36 × 12 in. (609 × screw-in-type, color-coded index discs. All outlets should be 914.4 × 304.8 mm) for washing large equipment. properly labeled. Serrated tips should be machined from solid The sink itself and sink outlet should be chemically resistant, stock or forgings. The service fittings should be chrome plated a minimum of 316 stainless steel, and so designed that a stopper over nickel plating or copper plating. The outlets in fume hoods or an overflow can be inserted and removed easily. The outlet should have an acid and solvent-resistant, plastic coating over should be removable and have a strainer to intercept any mate- the chrome-plated surface or be made of acid-resistant materirials that might cause a stoppage in the line. Unless an indus- als. Nonmetallic fittings are also available. trial water system is employed that isolates the laboratory water systems from the potable water system, via a central backflow- Special Equipment prevention device, all faucets should be provided with vacuum Dialysis machines Dialysis machines require a funnel drain or breakers. Supply fittings for distilled or deionized water are usu- floor sink and cold-water hose bibb with vacuum breaker. Heart-and-lung machines Heart-and-lung machines also ally either virgin plastic or tin lined and, where central systems require a funnel-type drain. If the apparatus is located in the are used, should be able to withstand higher pressures. Many operating room, an indirect waste is required. fitting types, especially PVC, can handle pressures up to but not Electron microscopes Electron microscopes require filtered, exceeding 50 psig (344.74 kPa). In these cases, pressure regulabackflow-protected, cold water or circulated chilled water. tion is required. Stills Stills for producing distilled water require cold water Cup sinks These are small, 3 × 6 in., 3 × 9 in., or 3 × 11 in. (76.2 with a vacuum breaker and floor sinks or funnel drains. × 152.4 mm, 76.2 × 228.6 mm, or 76.6 × 279.4 mm) oval sinks Sterilizers Sterilizers require an acid-resistant floor sink or for receiving chemicals, normally from a condensate or a supply funnel drains, a backflow-protected water supply and someline. They are designed to fit into the center section between the times steam and condensate connections. table tops; against a wall; or on raised, back ledges. These sinks Film-processing equipment Film-processing (x-ray) areas are also common in fume hoods. require an acid-resistant floor sink or funnel drains for indirect Laboratory glass washers are usually included, either furwaste; and a hot, cold and/or tempered water supply operatnished by the laboratory equipment supplier or selected by the plumbing designer. Automatic washers are available. In addi- ing between 40 and 90°F (4.4 and 32.2°C). Drain piping for any tion to waste or indirect waste services, these units require hot photo-developing equipment should not be brass or copper. water (usually 140°F [60°C] boosted to 180°F [82°C]) internal Polypropylene, high-silica, cast-iron, corrosion-resistant piping to the unit, distilled or deionized water, and compressed air. and drains should be used. Silver recovery and neutralization Manual-type glass bottle and tube washers may also be required may be required; consult with the local authority. Dental equipment Dental areas should include console serin these rooms. Tube washers may have manifold-type supply vices (water, air, medical gas, nitrous oxide and waste); and for fittings using cold water only. The manifolds can be fitted with a oral surgery a separate surgical vacuum system should be pronumber of individually serrated tip outlets provided with sepavided. rate controls and vacuum breakers. The plumbing engineer should always consult with the equipEmergency showers should be included throughout and ment manufacturer’s authorized representative and the local located in the adjacent corridors or at the door exits. The showadministrative authority, in order to determine the equipment ers must be accessible, require no more than 10 s to reach, and requirements and the acceptability under the jurisdiction’s be within a travel distance of no greater than 100 ft (30.5 m) from applicable codes, during the preliminary design. the hazard rooms. The shower head is a deluge-type shower with a 1-in. (25.4 mm) nominal cold water, stay-open design, supply valve operated by a hanging pull rod, or a chain and pull ring, or a pull chain secured to the wall. A floor drain may be provided, if required. If floor drains are provided, trap primers should be incorporated. Eye and face-wash fountains are also required. These are wall or counter-mounted units with a foot-pedal or wrist-bladehandle-operated, water-supply fixture; double side-mounted, full face-wash outlets; or deck-mounted, hand-held (with hose) 60 Plumbing Systems & Design

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Drainage Systems for Laboratories In addition to the conventional sanitary drainage systems (those found in most buildings), special sanitary drainage systems may be required in health-care facilities. Insofar as possible, drainage piping shall not be installed within the ceiling or exposed in operating or delivery rooms, nurseries, food-preparation centers, food-serving facilities, food-storage areas, central services, electronic data-processing areas, electric closets, and other sensitive areas. Where exposed, PSDMAGAZINE.ORG

overhead drain piping in these areas is unavoidable, special pro- sensors can be installed between the pipe walls that can pinpoint Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com visions shall be made to protect the space below from leakage, the original leak location. The latter could reduce the amount of condensation, or dust particles. excavation or exploration required to find the leak. Acid-Waste Drainage Systems Acid-waste drainage systems require special design criteria because the corrosive solutions demand special handling from the actual work area to an approved point at which such acid waste (and fumes) can be safely neutralized and discharged. The plumbing engineer must exercise extreme care in this regard. Acid-resistant waste and vent systems are necessary where acids with a pH lower than 6.5 or alkalis with a pH greater than 8.5 are present. These special conditions are commonly encountered in hospitals, research facilities, and laboratories. Since acid fumes are often more corrosive than the liquid acids themselves, proper drainage and venting is imperative. Nationally recognized standards for sanitary systems that handle acid wastes and other reagents are set forth in model plumbing codes; such systems are often further regulated by local building and safety or health department requirements. For these reasons, the plumbing engineer should check for all special design conditions that may affect the project. Strong acids and caustics may enter the sanitary-waste system in large quantities and at elevated temperatures. These substances can mix to form highly corrosive and even dangerous compounds. Common laboratory procedures encourage neutral ization or flushing with copious amounts of water in order to dilute and cool these chemicals to more acceptable levels. However, the plumbing engineer must protect the acid-waste system by designing for the maximum hazard conditions that might be brought about by any human error, poor housekeeping, or acci dental spillage. Corrosive-Waste Systems Materials Borosilicate glass pipe Sizes range from 1½ to 6-in. (40 to 150mm) pipe. Mechanical joint, flame resistance, and clear pipe allow for easy visual inspection and high corrosion resistance. High-silicon cast iron Sizes range from 1½ to 4-in. (40 to 100-mm) pipe. Mechanical joint, flame resistance, high corrosion resistance, fire stop at floor penetration equal to cast iron. More fragile and heavier than standard-weight cast iron and easier to break in the field. Excellent application for moderate to high-budget project. Polypropylene Sizes range from 1½ to 6-in. (40 to 150-mm) pipe. Mechanical or heat-fusion joints. Mechanical joints are not recommended for straight runs or sizes over 2 in. (50 mm); they should be used to access p-traps or other maintenance areas. Flame resistant and acceptable within most jurisdictions (meets 25/50 flame/smoke criteria), newer UL listed methods are close to glass in cost. Consult local authority for approval. Light weight and easy to install. Good application for moderate acids at low temperatures. Must be installed by qualified technicians. Inexpensive compared to borosilicate glass or high-silicone cast iron. Double-containment waste piping With ever-increasing pressure to protect our environment, double-containment (pipe within a pipe) systems have become a consideration. Usually made of polypropylene inside and PVC or fiberglass outside. Systems should be pitched toward a containment vault for collection of leaking fluid. Alarm systems can be employed to detect leaks at the collection basin or, if the budget and the nature of the liquid allow,

Discharge to Sewers Many local jurisdictions require that the building’s sanitarysewer discharge be at an acceptable pH level before it can be admitted into a sanitary-sewage system. In such cases, it is recommended that a clarifying (or neutralizing) tank be added to the sanitary system. Small ceramic or polypropylene clarifiers with limestone can be located under casework for low flow rates; however, sufficient space must be allowed above the unit for servicing. Unless properly maintained and monitored, this type of system can be rendered ineffective. Large clarifiers and neutralizers may be regulated by the requirements of a local industrial-waste department. Acidic-Waste Neutralization The lower the pH number, the Table 2 Acidic-Waste Neutralization higher the concentration of acid. Tank Sizing Table Discharging high concentrations Number of gal (L) Lab Sinks of acid into a public sewer may 2 5 (18.9) cause considerable corrosion to 4 15 (56.8) piping systems and eventual fail8 30 (113.6) ure. Most local authorities do not 16 55 (208.2) allow acid wastes to be discharged 22 75 (283.9) to a public sewer without some 27 90 (340.7) form of treatment. 30 108 (408.8) 40 150 (567.8) The neutralization of acidic 50 175 (662.4) wastes is generally and most eco60 200 (757.0) nomically dealt with through an 75 275 (1,040.9) acid-neutralization tank. An acid110 360 (1,362.6) neutralization tank may be con150 500 (1,898.5) structed of polyethylene, molded 175 550 (2,081.8) stone, stainless steel, or another 200 650 (2,460.3) 300 1200 (4,542) acid-resistant material. Tanks are 500 2000 (7,570) sized to provide a dwell time of 2 to 600 3000 (11,355) 3 h (refer to Table 2). Limestone or Note: For commercial and industrial marble chips fill the interior of the laboratories, the number of lab sinks should be tank, helping to neutralize incom- multiplied by a 0.5 use factor. ing acid wastes. Chips may be 1 to 3 in. (25.4 to 76.2 mm) in diameter and should have a calcium carbonate content in excess of 90%. A discharge pH sensor and routine maintenance schedule must be provided to ensure that the system operates properly. Acid-Waste Solids Interceptor As with many sewer systems, it is impossible to control all materials discarded to the drain system. Unless building effluent is controlled, many unwanted items, such as glass fragments and needles, will find their way to the neutralization tank, thereby clogging the limestone or marble chips. When this happens, replacement of the chips is required. One way to prolong chip life is to install an acid-waste solids interceptor immediately upstream of the neutralization tank, although maintenance of the interceptor may have to be done quite frequently. Acid-Waste Metering Detail Many local authorities require some means of sampling effluent from industrial, institutional, and laboratory buildings. An example of a device used for this purpose is a sampling manhole. This unit is installed as the last component before neutralMARCH/APRIL 2006


CONTINUING EDUCATION: Plumbing Design for Health Care Facilities ized acidic wastes or treated industrial wastes are discharged Water-Supply Systems Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com to a public sewer. There are as many types of sampling point A domestic-water supply of adequate flow volume and presrequirements as there are municipal sewer authorities. Consult sure must be provided for all the plumbing fixtures and related local code authorities for individual requirements. equipment. Systems typically encountered in these types of facility are as follows: Traps for Laboratory Sinks The trap is recognized by most plumbing engineers as the weak- 1. Potable-water systems. A. Cold water. est link in the acid-waste system. The trap must be acid resisB. Hot water (at various temperatures). tant. If strong acids and solvents collect in an ordinary trap, failC. Chilled water. ure of the system will occur. Three types of acid-waste traps are D. Controlled-temperature (tempered) water. currently in common use: p-traps, drum traps, and centrifugal E. Hot water recirculation. drum traps. (Running and s-traps are not allowed by many local 2. Non-potable water systems. plumbing codes because of the potential for trap siphoning.) 1. P-traps maintain a water seal to keep the acid fumes from 3. Pure-water systems. reentering the work area. A. Distilled water. 2. Drum traps provide a greater water seal and are frequently B. Deionized (or demineralized) water. used to separate either precious metals or other matter C. Reverse osmosis. before they enter the drainage system to become lost or Health-care facilities should have dual domestic-water sercause a stoppage in the sink. Drum traps with removable vices installed to ensure provision of an uninterrupted supply bottoms should be installed high enough above the floor of water. The design should consider water-conservation profor servicing. P-traps, including some of the simple drum visions. Many local jurisdictions have strict water-conservatraps, can easily be back-siphoned if the head pressures are tion laws in effect. Water recycling may be a consideration for extreme. use in landscaping, etc., depending on local code and health3. Centrifugal drum traps are designed to prevent backdepartment regulations. (For more information, see Data Book, siphonage conditions. Volume 2, Chapter 2, “Gray-Water Systems.”) Water supply through a tank (suction or gravity type) should Laboratory Waste and Vent Piping be considered by the plumbing engineer when the water-supply Sizing for under-table waste and vent piping, as determined by source may be subjected to some unusual demands, pressure the local plumbing codes, should be suitable for the installation fluctuations, and/or interruptions that will cause a sudden excesand allow for future expansion. Approved corrosion-resistant sive draw and pressure loss on the main system. The tank will act piping should be used for vent piping as well, since acid fumes as a buffer. Inadequate flow and pressure require the design of a are also highly corrosive. Space is often limited under tables water-storage tank and/or a booster pump for the water-supply and in vent areas. The space-saving features of mechanical joint system. Excessive pressure fluctuations are highly undesirable in piping have proven to be useful in many installations. medical-research laboratories. When such facilities are supplied Note: When fusion-joint, plastic piping systems are used, from street pressure systems, the engineer may provide pressuremechanical joints should be installed at traps and trap arms for reducing valves on the branch lines, or a gravity tank system. maintenance reasons. Use of diversity factors for sizing the water systems must be Special island (or loop) venting is frequently used when cabicarefully analyzed by the designer. Medical-school laboratory nets or work tables are located in the center of the laboratory classrooms have higher rates of simultaneous use than most area. research laboratories. Emergency rooms, out-patient treatment The transportating of acid waste, above and below the ground, rooms, and operating-room wash-up areas also have high rates must be done in approved, corrosion-resistant piping (acceptof simultaneous use. able to the local administrative authority) and continued to a Extreme care must be taken in order to protect the potablesuitable point where neutralization can occur or where suffiwater supply from contamination (cross connection). When cient water or chemicals can be introduced to bring the pH level an industrial (non-potable) system is not present, the engineer of the solution to an acceptable level. Acids below a pH of 6.5 should specify the appropriate type of vacuum breakers (neces normally may not be admitted into the sanitary-sewage system sary for each fixture below the rim connection), hose-end outlet, or emitted into surrounding soil, polluting (or degenerating) and an aspirator or other serrated-tip laboratory outlet, whether local ground water. High-silicon cast iron with hub-and-spigot they are required by the local plumbing regulations or not. The joints may be caulked with teflon, or neoprene gaskets may be vacuum breakers provided for fume-hood outlets should be used for sealing. This type of joint will allow flexibility and, when located outside the hood. Built-in (or integral) vacuum breakers properly supported, is particularly recommended on the horiare preferred to the hose-end type units. zontal runs where the expansion and contraction of pipe from heated chemicals can cause leaking. Plumbing codes require Potable-Water Systems proper bed preparation and careful backfilling on all below- Cold water should be provided at all required locations. The hot water should be generated with the most economical heating ground piping, particularly plastic piping. The plumbing engineer should check the manufacturer’s rec- medium available. With today’s technology, several reliable methods can be ommendations in order to evaluate the severity of the chemicals to be used. A listing of the common chemicals and how these applied to produce and store domestic hot water. Refer to substances react with the various materials must be considered ASPE’s Domestic Water Heating Design Manual and ASPE Data Book Volume 2, Chapter 6, “Domestic Water-Heating Systems,” by the designer. 62 Plumbing Systems & Design

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for in-depth explanations of design methods for hot-water sys- are usually required in the hospital’s pharmacy, central-supply Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com tems and a discussion of the various hot-water systems avail- room, laboratories, and laboratory-glassware washing facilities. able. When large “dump” loads are anticipated (kitchens and There are two basic types of pure water available in hospital laundries), storage of hot water is recommended. Hot-water facilities: bio-pure water (water containing no bugs or other usage in patient-care areas requires consideration of water tem- life forms) and high-purity water (pure water that is free from perature and bacterial growth. The most common water-borne minerals, dissolved gases, and most particulate matters). Refer bacterium of concern is Legionella pneumophila. to ASPE Data Book, Volume 2, Chapter 11, “Water Treatment, Recommended water temperatures for specific applications Conditioning, and Purification,” for additional information on are as follows: water purity. Water purity is most easily measured as specific resistance (in 1. Patient-care and hospital general usage requires water temohm-centimeter [Ω-cm] units) or expressed as parts per milperatures between 105 and 120°F (40.5 and 49°C), except where the local plumbing codes or other regulations require lion (ppm) of an ionized salt (NaCl). The theoretical maximum specific resistance of the pure water is given as 18.3 MΩ-cm at other maximum temperatures. Hot‑water distribution 77°F (25°C). This water purity is difficult to produce, store, and systems serving patient-care areas shall be under constant distribute. This water is “starved” for impurities and constantly recirculation to provide continuous hot water at each attempts to absorb contaminants. It is important to note that hot-water outlet. The temperature of hot water for bathing the specific resistance of the pure water is indicative only of its fixtures and hand-wash lavatories shall be appropriate for mineral contents and in no way shows the level of bacterial, comfortable use but shall not exceed 120°F (49°C). pyrogenic, or organic contamination. An independent labora2. Kitchen general usage requires 140°F (60°C) to fixtures, tory analysis should be made, whenever possible. except the dishwasher’s sanitizing cycle. The sanitizing The five basic methods of producing pure water are as follows: cycle requires 180 to 190°F (82 to 88°C) to the dishwasher, distillation, demineralization, reverse osmosis, filtration, and with 180°F (82°C) minimum required at the dish rack. recirculation. Depending upon the type of pure water required (Consult local health-department regulations.) Also, some in the facility, one (or more) of these methods will be needed. health departments set a maximum temperature of 105 to Under certain conditions, a combination of several methods 120°F (40.5 to 49°C) for hand-washing lavatories. may be necessary. 3. Laundry facilities should be supplied with two water tem1. Distillation produces bio-pure water, which is completely peratures, 140°F (60°C) for general usage and 160°F (71°C) free from particulate matters, minerals, organics, bacteminimum to washers/extractors for laundry sterilizations. ria, pyrogens, and most of the dissolved gases and has a Providing a point-of-use booster heater for high-temperature minimum specific resistance of 300,000 Ω. An important applications instead of a central water-heater system is often more consideration in this case is that the water is free from baceconomical. teria and pyrogen contamination, which is dangerous to A closed system of chilled water may be required for the coolthe patients, particularly where intravenous solutions are ing of electron microscopes and x-ray tubes and should be of a concerned. Bio-pure water is needed in the hospital’s pharrecirculating design. macy, central-supply room, and other areas where there Film processors operate at a normal range of 40 to 30°F (4.4 may be patient contact. Bio-pure water may also be desired to –1.1°C). Some models do require controlled water temperain certain specific laboratories at the owner’s request and as ture for film processing. Depending on the quality of the water a final rinse in the laboratory’s glassware washer. supply, a 5 to 75-µ filter may be required. The typical water-distillation apparatus consists of an A thermometer should also be provided on the outlets of evaporator section, an internal baffle system, a waterwater heaters and thermostatically controlled valves. A pressure cooled condenser, and a storage tank. The best material for regulator, gauge, and flow meter may also be desired on the inlet its construction is a pure block-tin coating for both the still side of pressure-sensitive equipment. and the tank. The heat sources, in order of preference based Non-Potable Water Systems on economy and maintenance, are as follows: steam, gas, Non-potable water systems are usually employed in areas and electricity. The still may be operated manually or autohaving multiple water requirements that could contaminate the matically. The distilled water may be distributed from the potable-water supply. Areas in this category include: flushingstorage tank by gravity or by a pump. A drain is required for rim floor drains in animal rooms, all outlets in autopsy rooms, system drainage and flushing. On stills larger than 50 gph outlets in isolation rooms, and all outlets in infectious-disease (189.3 L/h), a cooling tower should be considered for the and tissue-culture rooms. These systems normally use reducedcondenser water. pressure-type backflow preventers as the means to protect the 2. Demineralization, sometimes called “deionization,” propotable-water system. Hot water, when required, may be produces high-purity water that is completely free from minervided by a separate generator supplied from the non-potable als, most particulate matters, and dissolved gases. Dependwater system. ing upon the equipment used, it can have a specific resisPure-Water Systems tance ranging from 50,000 Ω to nearly 18 MΩ. However, it “Pure water” is the term generally used to describe water that could be contaminated with bacteria, pyrogens, and organis free from particulate matters, minerals (soluble ions), bacteics (these contaminants may be produced inside the deminria, pyrogens, organic matters, and dissolved gases, which freeralizer itself ). Demineralized water can be employed in quently exist in the potable water supply. Pure-water systems MARCH/APRIL 2006


CONTINUING EDUCATION: Plumbing Design for Health Care Facilities most laboratories, the laboratory’s glass-washing facilities 2. Clean joining methods—avoid solvents, lubricants, and Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com (as a final rinse) and as the pre-treatment for still feedwater. crevices. The typical demineralizer apparatus consists of either 3. No material erosion—must not flake off particles. a two-bed deionizing unit (with a resistivity range of 4. Material should not enhance microorganism growth. 50,000 Ω to 1 MΩ) or a mixed-bed deionizing unit (with a 5. Material should be smooth, crack and crevice-free, and resistivity range of 1 to 18 MΩ). The columns are of an inert nonporous. material filled with a synthetic resin, which removes the 6. Avoid dead legs—system should have continuous flow minerals by an ionization process. Since the unit operates through piping. on pressure, a storage tank is not required or recommended 7. Provide chemical cleaning connections. (as bacteria will grow in it). A demineralizer must be chemically regenerated periodically, and during that regeneration 8. Install (slope) with future cleaning and disinfection in mind. time no pure water is produced. If a continuous supply of pure water is needed, a backup unit should be considered A wide variety of piping materials are available on the market by the engineer, as the regeneration process takes several today. Their properties and cost cover a wide range. hours. The regeneration process can be done manually or Common pure-water materials automatically. An atmospheric, chemical-resistant drain is 1. Stainless steel—various grades (304L & 316L). required. High-flow water is required for backwash during 2. Aluminum. the regeneration. 3. Tin-lined copper. 3. Reverse osmosis (RO) produces a high-purity water that does 4. Glass or glass-lined pipe. not have the high resistivity of demineralized water and is 5. PVC/CPVC—Polyvinyl chloride/chlorinated polyvinyl chlonot bio-pure. Under certain conditions an RO process can ride. offer economic advantages over demineralized water. In areas that have high mineral contents, an RO process can be 6. Polypropylene. used as a pre-treatment for a demineralizer or still. 7. Polyethylene. There are several types of reverse osmosis units currently 8. ABS—Acrylonitrile butadiene styrene. available. Units consist of a semipermeable membrane, in 9. PVDF—Polyvinylidene fluoride. either a roll form or a tube containing numerous hollow Metal pipe Aluminum, tin-lined copper, and stainless-steel fibers. The water is then forced through the semipermeable pipe have all been used in pure-water treatment systems. Tinmembrane under high pressure. A drain is required with lined pipe was once the material of choice in ultra-pure water these systems. systems. However, it does leach tin and eventually copper into Note: Chlorine must be removed from the water, otherwise the process fluid. Methods of joining tin-lined pipe can also it will destroy the RO membrane. leave non-smooth joints with crevices. Aluminum pipe has also been used in pure-water systems. 4. Filtration Various types of filter are currently available Pure water creates an oxide layer inside the pipe that continuto remove the particulate matters from the water as a preally erodes, producing particles and aluminum in the water. treatment. Depending upon the type of filter, a drain may Stainless steel has been used extensively in high-purity water be required. Bacteria may be eliminated through ultraviolet systems. It can be joined with threads, butt welded, flanged, or sterilization. manufactured with sanitary-type connection ends. Because 5. Recirculation High-purity systems should be provided it can use sanitary joints and can handle steam sterilizing, the with a circulation loop. Dead-end legs should be avoided sanitary-type connection method has been used in many pharwhenever possible or limited to 50 in. (1.52 m). System design velocity should be between 4 and 7 fps (1.22 and 2.13 maceutical applications. However, experience has shown that even the best grades of stainless steel, with the best joints, still m/s) so as to discourage bacteria accumulation and provide leach material from the metal that can cause problems in crititransport back to an ultraviolet sterilizer and filtration for cal water systems. removal. Glass or glass-lined pipe Glass piping has been used in some Pure-water piping system materials Water-treatment special laboratory applications but, because it is fragile and system components are selected to remove various impurities does leach material into the water, it is not generally considered from the influent water. Connecting various system components applicable for high-purity water systems. together involves the use of interconnecting piping. The use of PVC PVC pipe has been used on equipment and in piping this piping should not contribute to adding any such impurity systems successfully for many years. Advances in technology, back into the treated water. especially in electronics, have now raised questions about the Selection of piping-system materials is determined by the “true purity” or inertness of PVC. application intended, the availability of the material, and the PVC pipe contains color pigments, plasticizers, stabilizers, cost of the material. Pure-water applications, such as exist in the and antioxidants that can all leach out of the plastic and into health-care industry, can be very sensitive to the piping meth- ultra-pure water. Remember that 18,000,000-Ω quality water is ods selected. highly aggressive. When PVC pipe is made (extruded), bubbles General pure-water piping requirements include: of air exist, some of which are covered over with a thin film of 1. Inert materials—must not leach contamination into water. PVC on the interior walls of the pipe. As the pipe ages, these thin coverings wear away, exposing small holes which then serve as 64 Plumbing Systems & Design

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debris-collecting or microorganism-breeding sites, not to menABS has some of the same contamination leach problems as Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com tion the contribution of PVC particles and the potential release PVC. In its manufacture, pigment dispersants, surfactants, styof organic dispersants, stabilizers, etc., originally trapped in rene, and other additives are used that can leach into water over these bubbles (holes). time. Hydrogen peroxide (used for system cleaning) will also Joints, either solvent welded or threaded, can leave crevices attack ABS plastic. for the accumulation of particles and bacteria. Solvents from the PVDF There are numerous types of high-molecular-weight weld can also leach into the water. fluorocarbon pipes on the market, SYGEF, KYNAR, and HALAR, Premium grades of PVC, which reportedly have fewer leach- to name a few. Polyvinylidene fluoride (PVDF) plastic can be ables than standard PVC, are now being marketed. extruded without the use of additives that can leach out later. CPVC is a special high-temperature PVC that has similar ero- The different polymerization techniques used by each manusion and leachable characteristics. facturer can produce slightly different properties. Polypropylene Polypropylene is a very inert, strong piping PVDF pipe is currently considered to be the state of the art material. However, in the manufacture of the pipe antioxidants in pure-water piping systems. It has exceptional chemical resisand other additives are used to control embrittlement. These tance; temperature range, –40 to 320°F (–40 to 160°C); impact additives are potential sources of contaminants that can leach strength; resistance to UV degradation; abrasion resistance; and into the water. However, a virgin material with no leachable smooth, clean, inside surfaces that discourage the collection of products is now available. bacteria and particles. Most laboratory test reports show virtuPolypropylene pipe shows good ability to withstand both cor- ally zero leachables from PVDF piping systems. rosive chemicals and high temperatures, up to 220°F (104°C). PVDF pipe is joined by the butt-fusion method, resulting in The natural toughness of the material minimizes damage to clean, smooth joints. pipe during installation and service. When system pressures exceed 70 psig (482.6 kPa) or temPolypropylene is generally joined by the butt-fusion method, peratures exceed 75°F (24°C), plastic piping system manufacresulting in smooth joints. turers should be consulted for compatibility. Polypropylene ABS Acrylonitrile butadiene styrene (ABS) plastic pipe has or PVDF-lined metal piping systems may be incorporated to been used in the primary stages of water-treatment systems meet pressures up to 150 psig (1034.2 kPa). ✺ because of relatively low cost and ease of installation.

MARCH/APRIL 2006



Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PS&D), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status. ASPE features a technical article in every issue of PS&D, excerpted from its own publications. Each article is followed by a multiplechoice test and a simple reporting form. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of 90% or higher on the test, you will be notified that you have logged 0.1 CEU, which can be

applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years. No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PS&D within the past 12 months. However, CEU credit only can be obtained on a total of eight PS&D articles in a 12-month period. Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

CE Questions—“Plumbing Design for Health Care Facilities” (PSD 132) 1. High-silicon cast iron pipe is _________ than standard weight cast iron pipe. a. lighter b. heavier c. more costly d. less costly 2. Fixture-unit values for unique fixtures found in health-care facilities can be _________. a. estimated b. assigned by the authority having jurisdiction c. higher then anticipated d. found in Table 2-2 3. The theoretical maximum specific resistance of pure water is _________ ohm-centimeter units at 77oF. a. 12.6 b. 16.8 c. 18.3 d. 20.2 4. Hand washing lavatories are not required in _______. a. family waiting rooms b. janitor’s closets c. outpatient services areas d. nurses’ stations 5. A review of applicable code requirements is ________. a. always required b. is under the jurisdiction of the Joint Commission of the Accreditation of Hospital Organization (JCAHO) c. restricted to local codes only d. is not necessary for the experienced plumbing engineer 6. When referring to acid waste, the lower the pH number, the _________ the concentration of acid. a. lower b. higher c. more neutral d. none of the above


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7. It is common for architects to locate the piping shafts and the spaces in direct conflict with the structural framing because _________. a. they do not know any better b. it serves their purpose c. the plumbing designer has not given the architect direction regarding space requirements d. none of the above 8. What type of vent system is used on laboratory sinks that are located in the center of laboratory areas? a. end vent b. stack vents c. loop vents d. crown vents 9. What is the size, in liters, of an acid waste neutralization tank that serves 75 laboratory sinks? a. 1,020.9 b. 1,040.9 c. 1,050.9 d. 1,060.9 10. This chapter discusses _________. a. the requirements of health care facilities b. the provisions that may be encountered by the plumbing professional in the design of a health care facility c. nursing homes, medical schools, and medical laboratories d. energy codes as they apply to medical facilities 11. X-ray areas require _________. a. tempered water b. corrosion-resistant piping and drains c. silver recovery d. a and b 12. Which of the following piping materials is not commonly used for the distribution of pure water? a. aluminum b. CPVC c. copper d. PVDF

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Continuing Education Application Form 1. Make a photocopy of this form. Leaving this page in PS&D allows others to use it to obtain continuing education units (CEUs). 2. PRINT your name and address. Be sure to place your membership number in the appropriate space. This form is valid up to 1 year from date of publication. The PS&D continuing education unit program is approved by ASPE for up to 1 contact hour (0.1 CEU) of credit per article studied. 3. Answer the multiple-choice continuing education (CE) questions (found after each CE article) and the appraisal questions on this page. 4. Submit this form and the answer sheet below, with the payment of the appropriate fee by check or money order made payable to ASPE, or submit the credit card information to ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656–1116. 5. Participants who earn a passing score (90%) on the CE questions will receive a letter of certification within 30 days of PS&D’s receipt of the application (no special certificates will be issued). (CEU information will be retained on the ASPE Database.) Participants who wish to retake the test should submit their retest along with an additional fee—$25 for an ASPE member (currently waived) or $35 for a nonmember. Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________ I am applying for the following continuing education credits:




Signature Expiration date: Continuing education credit will be given for this examination through March 31, 2007. Applications received after that date will not be processed.



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Plumbing Design for Health Care Facilities (PSD 132)





Plumbing Design for Health Care Facilities (PSD 132) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

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Irrigation Systems

PSD 141



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Irrigation Systems


Introduction The function of an automatic irrigation system is to provide and distribute a predetermined amount of water to economically produce and maintain ornamental shrubs, cultivated lawns, and other large turf areas. Other benefits of an automatic irrigation system include convenience, full landscape coverage, easy control for overnight and early morning watering, and minimized plant loss during drought. This chapter discusses the basic design criteria and components of irrigation systems for ornamental lawns and turf. Among the factors considered are water quality and requirements, soil considerations, system concepts, and system components. A design information sheet is also provided, as Appendix A, to assist the plumbing engineer in the orderly collection of the required field information and other pertinent data.

Water Quality and Requirements In urban areas, where the source of the water supply is often the municipal water system, the plumbing engineer does not need to be concerned with the quality of the water. In cases where private sources are used and the water quality is unknown, the water should be analyzed by the appropriate local health authority having jurisdiction prior to use. The three main areas of concern are as follows: 1. Any silt content that, if high, may result in the baking and sealing of soils 2. Any industrial waste that may be harmful to good growth 3. Any soluble salts that may build up in the root area The most common solution currently available for handling excessive amounts of silt is the construction of a settling basin, usually in the form of a decorative lake or pond. In those areas where the salt

Table 1 Net Amount of Water to Apply per Irrigation Cycle Soil Profile Amount, in. (mm) Coarse, sandy soils 0.45 (11.43) Fine, sandy loams 0.85 (21.59) Silt loams 1.10 (27.94) Heavy clay or clay loams 0.90 (22.86) Note: Net amount of moisture required based on 12 in. (304.8 mm) root depth.

content is excessive, 1,000 parts per million (ppm) and above, the inability of the soil to cope with the problem may require the use of special highly salt-tolerant grasses. The quantity of water required for an effective irrigation system is a function of the type of grass, the soil, and local weather conditions. The quantity of water is usually expressed as the depth of the water applied during a given period over the area to be covered. The amount of water applied to a given area can be controlled easily by adjusting the irrigation system’s length and frequency of opera-

Figure 1 Examples of a Block System

Reprinted from ASPE Data Book Volume 3: Special Plumbing Systems, Chapter 4: “Irrigation Systems.” © American Society of Plumbing Engineers. 2 Plumbing Systems & Design

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tion. An efficient irrigation system takes to be operated at any given time. Figure 3 Figure 2 Quick-Coupling Valve Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com into consideration the rate of the appliillustrates this design. cation of the water, usually expressed in System Components inches per hour, and the attempt to match Sprinklers the application rate with the absorption One of the most important considerations rate of the soil. Often, this condition is for the plumbing engineer when designachieved through frequent short watering an irrigation system is the selection of ing cycles. the sprinklers. Sprinklers are mechanical Soil Considerations devices with nozzles used to distribute Sandy, porous soils have relatively high water by converting water pressure to a absorption rates and can handle the high high-velocity discharge stream. Many output of the sprinklers. Steep slopes different types of sprinklers are manufacand very tight, nonporous soils require tured for a variety of system applications. low precipitation rates to avoid erosion The plumbing engineer should become damage and wasteful runoff. knowledgeable of the various types before A sufficient amount of water must be selecting the sprinklers, as the flow rates applied during each irrigation period to and operating pressures must be nearly ensure penetration to the root zone. Table the same in each of the irrigation system’s 1 suggests guidelines for several soil procircuits. files (net amount of water to apply per Spray Sprinklers Surface-type spray irrigation cycle). In the absence of any and pop-up spray sprinklers (see Figure specific information on the soil and local 4) produce a single sheet of water and weather conditions, the irrigation system cover a relatively small area, about 10 to 20 may be designed for 1½ inches (38.1 milfeet (3.05 to 6.10 meters) in radius. These limeters) of water per week. The plumbsprinklers can operate on a low-pressure ing engineer should consult with the local range of 15 to 35 pounds per square inch administrative authority to determine (psi) (103.4 to 241.3 kPa). They apply the compliance with the applicable codes in water at a high rate of application—1 to the jurisdiction. The engineer can obtain 2 inches/hour (25.4 to 50.8 mm/hour)— specific information on the soil and local and are most economical in small turf weather conditions by contacting a local or shrub areas and in irregularly shaped weather bureau, university, or state engiareas. neer. Due to the fine spray design, the pattern be considered by the engineer. An examSystem Concepts can be easily distorted by the wind; thereple of a quick-coupling valve is illustrated The three basic system concepts that can in Figure 2. be used by the engineer in the design The last concept in of an irrigation network are the block sprinkler system design Figure 3 Valve-in-Head System method, the quick-coupling method, and is the valve-per-sprinkler the valve-per-sprinkler method. method. Small actuator The block system is an approach in valves, operated at low voltwhich a single valve controls the flow of age, provide great flexibilwater to several sprinklers. It is ideal for ity and control. Sprinklers residential and other small turf areas. in diverse areas having the Either manual or automatic valves may same (or similar) water be used in the block system. As the irriga- requirements may be tion area increases or where high-volume operated concurrently. In sprinklers are employed, the block system other applications, such as becomes less attractive to the engineer quarter applications covbecause of the large valves and pipelines ering quarter circles or half required. Examples of the block system circles, the irrigation sprinare shown in Figure 1. klers may be piped, wired, The quick-coupling irrigation system and operated together is an answer to the high cost incurred on through system programlarge block system projects. Development mers. The valve-per-sprinof the quick-coupling valve provided a kler system provides the more flexible irrigation system. The valve opportunity to standardize is located underground but can be acti- the pipe sizes by selecting vated from the surface. Where manpower the appropriate sprinklers is not critical and security is reasonable, the quick-coupling irrigation system may SEPTEMBER 2007


CONTINUING EDUCATION: Irrigation Systems in both single-nozzle and

Figure 4 Pop-Up Spray Heads

Figure 6 Rotor Sprinkler—Arcs and Full Circles

Photo courtesy of Rain Bird Corporation

These devices can operate at a higher pressure (25 to 100 psi [172.3 to 689.5 kPa]) and cover larger areas (40 to 100 feet [12.2 to 30.5 meters] in radius). The water is applied at a lower rate (0.20 to 0.5 inches/hour [5.08 to 12.7 mm/hour]). Because of its larger, more compact stream of water, this sprinkler is not easily distorted by the wind and is most economical in large, open turf areas. Freestanding sprinklers are not desirable where they are exposed. In such cases, the pop-up, rotary-type sprinklers shown in Figure 6 may be used. These nozzles rise above the ground level only when the water is being delivered to the unit. Half-circle, rotary sprinklers can discharge the same volume of water as full-circle units. A half-circle, rotary sprinkler can provide the same amount of water as a full-circle unit over half the area, doubling the application rate. Quarter-circle sprinklers will quadruple the application rate. Some equipment manufacturers use different nozzles to compensate for the reduced area and to provide a uniform application rate. If compensating nozzles are not used in halfcircle sprinklers, these units must be valved and operated separately for a balanced application of the water. Shrub Sprinklers Several types of shrub sprinklers are available, including bubblers (see Figure 7), flat-spray sprinklers, and stream-spray sprinklers. Shrub sprinklers can be mounted on risers to spray over plants. If the plants are tall and not dense near the ground, shrub Photo courtesy of Rain Bird Corporation

Figure 5 Impact Sprinkler

fore, these sprinklers should be installed in protected areas. Impact Sprinklers Impact sprinklers (see Figure 5) can be permanent or movable and either the riser-mounted type (see Figure 2) or the pop-up rotary type (see Figure 6). Impact sprinklers have an adjustable, revolving water stream and are available 4 Plumbing Systems & Design

SEPTEMBER 2007


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com double-nozzle designs.

sprinklers can be used on short risers, and the spray can be directed under the plants. The spray can also be kept below the plant. Flat-spray shrub heads are best employed for these applications. Trickle Irrigation Trickle irrigation is commonly used in vineyards and orchards and routed through tubing with special emitters installed at each planting. Most emitters have flexible orifices and may have provisions for adding fertilizer. These irrigation systems have a low-volume usage and usually are not installed in conjunction with conventional lawn sprinkler systems. Valves Remote-control valves are generally classified into three basic categories: electric, hydraulic, and thermal-hydraulic. The electrically operated valve receives an electric signal from the controller and actuates a solenoid in the valve. This solenoid opens and closes the control valve. The hydraulic control valve is operated with the water pressure and has control tubing from the controller to the valve. The thermal-hydraulic control valve uses an electric signal from the controller to heat up the components of the valve to open the unit. The most common use of this valve is to control the water usage to the different zones. These devices should be installed with access for maintenance. Most control valves have some provisions for manual operation. In some systems, manual control valves are installed in pits or vaults

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surface mounted, recessed mounted, or

Figure 7 Nozzles—Adjustable Arcs and Patterns


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com pedestal mounted. Figure 9 shows a typi-

with a long T-handle wrench used for the activation of each circuit. An irrigation system may be installed with an automatic check valve on the sprinkler heads. When a zone is installed on sloping terrain, these valves will close when they sense a low pressure at turnoff, preventing the drainage of the supply pipe through a sprinkler head installed in a lower area. Atmospheric vacuum breakers (see Figure 8) must be installed on every sprinkler circuit downstream of the control valve to eliminate the possibility of back-siphonage into the potable water system. Many (if not all) local jurisdictions have codes that require this type of valve. The plumbing designer should consult with the local administrative authority and check all applicable codes for their requirements. Pressure-reducing valves are installed where higher street pressures are involved and also are commonly used to maintain a constant pressure where the inlet pressures may vary. Some manufacturers offer remote-control valves with pressure regulation. Low-flow control valves may be installed to avoid damage to the piping or tubing from pressure surges during the filling of a (dry) system. This control valve allows a slow filling of the piping or tubing until the pressure is established. In climates where freezing conditions may occur, automatic-type drain valves should be installed at the low points of the system to allow for drainage of the system. This control valve will open automatically when the water pressure drops below a set point. In heavy or dense soils, a pit of gravel should be provided for quick drainage.

ing drainage of the supply pipe through a sprinkler head installed in a low area. The use of pressure vacuum breakers to eliminate the possibility of backsiphonage into the potable water system is the minimum level of backflow prevention accepted by most jurisdictions. The plumbing engineer should consult with the local administrative authority and check all applicable codes for their requirements. Controllers Presently, many types of controllers for irrigation systems are available. Selection of this device is based on the specific application involved. Controllers are programmed to activate each irrigation zone at a specific time and also will control the length of time that each zone is activated. Some controllers have a calendar that allows the irrigation system to be used only on certain days. Other types of controllers have manual (or automatic) overrides to shut down all systems during rain or to turn on specific zones for extra water. Some controllers have soil moisture monitors, which turn on zones only when needed. Controller panels can be

cal illustration of a surface-mounted and a pedestal-mounted irrigation system programmer.

Design Information When designing an underground sprinkler system, the plumbing engineer should consider the following factors: the site plan, type of plants, type of soil, type and source of water, and system location. Site Plan An accurate site plan, preferably laid out to scale and showing all buildings, shrubs, trees, hedges, walks, drives, and parking, should be drawn as accurately as possible. Areas where overspray is undesirable, such as walkways and buildings, should be clearly noted. Property lines also should be shown on the site plan. The heights and diameters of shrubs and hedges should be indicated. Types of Plantings The engineer should show the areas that will be irrigated on the site plan as well as the areas that will be omitted. Those areas that require a different style of sprinkler and separate zoning also should be indicated. Some plantings require more frequent watering than others; therefore, they will require a separate zone and control valve. The engineer should determine whether the plantings allow spray on their leaves (or any other special type of spray) and should select the sprinklers accordingly.

Figure 8 Installation of Atmospheric-Type Vacuum Breakers

Backflow Devices An irrigation system may be installed with an automatic check valve on the sprinklers. When a zone is installed on sloping terrain, these valves will close when they sense a low pressure at turnoff, preventSEPTEMBER 2007


CONTINUING EDUCATION: Irrigation Systems System Location

Figure 9 Irrigation Sprinkler Programmers


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Type of Soil The type of soil determines the proper rate of application of water to the soil. The length and frequency of the applications can be determined by considering the soil and the types of plants. A sufficient amount of water must be applied during each irrigation period to ensure penetration to the root zone. Table 1 recommends acceptable guidelines for several types of soil profiles. Where available, the engineer should secure local soil and weather conditions by contacting the local state extension engineer, a university, or the weather bureau. The local weather bureau usually publishes an evapotranspiration guide, which shows the deficit water required to maintain turf grass. This value is compiled by measuring the rainfall minus the evaporation taking place during a particular period. The balance is the amount of water required. In the absence of any specific information on local soil and weather conditions, the irrigation system should be designed for


SEPTEMBER 2007

a minimum of 1½ inches (38.1 mm) of water per week. Sandy, porous soils (as previously indicated) have relatively high absorption rates and can handle the high output of sprinklers. Steep slopes and very tight, nonporous soils require low precipitation rates to avoid erosion damage and runoffs. Type and Source of Water The source of the water should be located on the site plan. If the water source is a well, the pump capacity, well depth, pump discharge pressure, and other pertinent data should also be recorded. If the water source is a city water main, the locations, size, service-line material, and length of piping from the service line to the meter should be researched by the plumbing engineer. The water meter size and the static water pressure of the city main are also needed. The engineer should determine whether special meter pits or piping arrangements are required by the utility company.

local climatic conditions, the general area may require specific design considerations, such as drain valves on systems subjected to freezing temperatures. Windy areas require closer spacing of sprinklers, and the wind velocity and direction must be considered. For areas on sloping terrain, there will be a difference in the outlet pressure, and consideration must be made for system drainage. The engineer must review local codes to determine acceptable piping materials, installation, requirements, and the approved connection to municipal water works. ✺

References The ABCs of Lawn Sprinkler Systems. Irrigation Association, Fairfax, Virginia. Pair, Claude H., ed. Sprinkler Irrigation, 4th edition. Sprinkler Irrigation Association, Silver Spring, Maryland. Architect-engineers Turf Sprinkler Manual. The Rainbird Company, Glendora, California. Design Information for Large Turf Irrigation Systems. The Toro Company, Riverside, California. Young, Virgil E. Sprinkler Irrigation Systems. Mister Rain, Inc., Auburn, Washington.

Resources The Irrigation Association, www.irrigation.org

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Appendix A


Suggested Information Sheet for Sprinkler System Design

All available information should be contained on this sheet, plot plan, or both. 1. Project name_______________________________ Address_______________________________________ 2. Water supply: a. Location and size of existing tap, meter, pump, or other __________________________________

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

b. Existing meter, pump, or tap capacity: Residual pressure _______________GPM _____________

c. Power supply: Location _________________________________________ Voltage _________________

d. Length, type, location, and size of existing supply line (identify on plan) Area to be watered. Identify all planted areas whether shrubbery or trees; indicate clearance under trees. (Identify on plan.) Soil type: Light _______________________ Medium _____________________ Heavy __________________ Hours per day and night allowed for irrigation __________________________________________________ Amount of precipitation required per week __________________________________________________ Area to be bordered or not watered (identify on plan) Elevations and prevailing wind conditions (identify on plan) Type of system: (a) Automatic electric _________________ (b) Automatic hydraulic _______________ (c) Manual pop-up ______________ (d) Manual quick-coupling _____________ (e) Other____________ Indicate equipment preference _____________________________________________________________ Indicate preferred location for valves and controllers _________________________________________________________________ ______________________________________________________________ Indicate vacuum breaker and/or drain valve requirement ____________________________________________________________ _________________________________________________________________ Indicate pipe material preference: 2½” and larger ______________ 2” and smaller _______________ Indicate any preference for sprinkler riser types ____________________________________________

Special Notes (use additional sheet if necessary)______________________________________________________________________ ____________________________________________________________________________________________________________________ ____________________________________________________________________________________________________________________ ____________________________________________________________________________________________________________________

SEPTEMBER 2007


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson

Now Online!


About This Issue’s Article The September 2007 continuing education article is “Irrigation Systems,” Chapter 4 of ASPE Data Book 3: Special Plumbing Systems. This chapter discusses the basic design criteria and components of irrigation systems for ornamental lawns and turf. Among the factors considered are water quality and requirements, soil considerations, systems concepts, and components. A design information sheet is also provided, as Appendix A, to assist the plumbing engineer in the orderly collection of the required field information and other pertinent data. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Irrigation Systems” (PSD 141) 1. The function of an irrigation system is _________. a. to conserve water b. as a labor-saving device for yard maintenance c. to provide and distribute a predetermined amount of water to economically produce and/or maintain shrubs, lawns, and turf d. none of the above 2. When designing an underground sprinkler system, the plumbing engineer should consider which of the following factors? a. site plan, b. types of plants, c. type of soil, d. all of the above 3. The amount of water to apply per irrigation cycle in coarse, sandy soil, assuming a 14-inch root depth, is ____. a. 0.45 inch, b. 0.85 inch, c. 1.10 inches, d. none of the above 4. The three basic concepts that can be used by the engineer in the design of the irrigation network are _________. a. block method, quick-coupling method, and valve-persprinkler method b. uniform water coverage, controlled depth of water per square foot, and zone control method c. both a and b d. none of the above 5. Water for irrigation systems _________. a. may be from an urban source b. may be from a private source c. may be from a storage reservoir, tank, or surface pond d. any of the above 6. Soil conditions _________. a. need not be considered when urban sources of water are used b. affect the amount of water needed c. are not important because the landscaper will supply the proper soil for the plants used d. should have high absorption rates


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PSD 141


7. The last concept in sprinkler system design is _________. a. plant type, b. soil type, c. the valve-in-head method, d. slope of grade at the site 8. One of the most important considerations for the plumbing engineer when designing an underground sprinkler system is _________. a. the selection of the sprinkler heads b. the system controller c. using a sufficient quantity of water d. using the least amount of water 9. Windy areas require _________. a. more water due to evaporation b. closer spacing of sprinklers c. increased outlet pressure d. both a and c

10. Atmospheric vacuum breakers must be installed _________. a. only if required by code b. on every sprinkler circuit downstream of the control valve c. when the designer does not want to use a backflow preventer d. below grade 11. Trickle irrigation is commonly used in _________. a. vineyards and orchards b. where water is scarce c. foreign countries d. less affluent areas

12. In climates where freezing conditions may occur, _________. a. manual drain valves should be installed b. reduced-pressure backflow preventers should not be installed c. automatic-type drain valves should be installed d. the piping system must be heat traced

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Simpo PDFSystems Merge and Unregistered Version - http://www.simpopdf.com Plumbing &Split Design Continuing Education Application Form This form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who earn a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required). 1. Photocopy this form or download it from www.psdmagazine.org. 2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space. 3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form. 4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656) or fax (773-695-9007). Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________

I am applying for the following continuing education credits:




Signature Expiration date: Continuing education credit will be given for this examination through September 30, 2008. Applications received after that date will not be processed.



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Irrigation Systems (PSD 141)



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Appraisal Questions

Irrigation Systems (PSD 141) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No 6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________ 1. 2. 3. 4. 5.

SEPTEMBER 2007



PSD 129

Jail and Prison Housing Units


SEPTEMBER/OCTOBER 2005

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Jail and Prison Housing Units INTRODUCTION The objective of this chapter is to help the designer understand and deal with the problems of designing water heating systems for jail and prison housing units. It is important that the designer recognize that each building is unique and work closely with the owner, architect, and government authorities to determine how a building will operate. A building’s operation will affect when and for how long the peak hot water demand will occur. The first part of this chapter discusses generally some of the design criteria and areas of special concern involved in designing for jail and prison housing units. The second part gives two practical examples of sizing methodology, one for jails and one for prisons. GENERAL The design criteria used to design hot water systems for jail housing units differ from those used for prison housing units. This difference is due to the fact that the facilities are used for different purposes. Jails are used primarily to house people awaiting trial or serving short sentences. Prisons are used to house convicted criminals serving long prison terms. This difference affects the prisoners’ daily routines, which, in turn, determine when the facilities’ peak hot water demands occur. It is required that hot water temperature for the showers and lavatories in jails and prisons be limited to between 100 and 110°F (38 and 43°C). This temperature range has been estab lished to prevent inmates from using hot water as a weapon.1 The generally used standard temperature is 105°F (41°C). Push-button type self-closing or timed-control valves are used to deliver hot water of this temperature to the showers and lavatories. Occasionally an owner will require that a shower control valve that allows some inmate control of shower water temperature be provided. New security type valves provide this feature. Hot water at the design temperature must be furnished at the fixture because of the lower-than-usual water temperature and the self-closing features of inmate control valves. The designer should take into consideration that the typical life of a jail or prison is 50 to 100 years and that any system installed must be accessible for replacement or repair. Large jail facilities and all prisons have central laundry facilities and central kitchens. The hot water systems for the laundry and kitchen areas should be separate from those for housing because these areas have very different hot water demands. For instance, the temperature of the hot water delivered will be higher, between 140 and 180°F (60 and 82°C). If a centralized water heating system is used for the general purpose and kitchen/laundry water, then a fail-safe water tempering system must be installed for the general purpose water.

Note: All decimal equivalencies in the metric calculations are rounded. Therefore, the metric conversions shown in the text may vary slightly from the answers shown in the metric equations.

Hot Water Demand The usual fixtures requiring hot water found in housing units are showers and lavatories. Some units also have small kitchens or serving areas, which may have additional sinks and small dishwashers. Such serving areas are project specific. In jails, very often one or two residential type washing machines are required for each housing unit pod (a group of 10 to 20 cells). The typical housing unit is composed of multiple pods, with each cell opening onto a day room. Currently it is recom mended that there be one shower for every eight inmates and a lavatory in each cell.2 The number and location of the showers are decided by the architect in coordination with the owner and according to specific code requirements. The shower operation is the factor that determines the required sizes of the water heater and storage tank. Primary considerations 1. The standard recommendation of eight inmates per shower was made so that all inmates could shower during a 1-h period. This arrangement allows an average of 7 min for each inmate to shower. About half that time is taken up by drying and switching inmates, leaving only about 3.5 min of actual water usage per inmate. 2. Showers are the main factor affecting water heater size. Allowance should be made for the many lavatories in housing units when sizing the storage tank. 3. The efficiency of storage systems varies from manu facturer to manufacturer, but 65 to 80% is a good efficiency range to use until you have actual data on the tank and system specified. JAIL EXAMPLE This is an example of a jail housing unit with six pods of 24 cells each (one inmate per cell) and three showers per pod. Assume that the hot water generated is 140°F (60°C) and the incoming water temperature is 50°F (10°C). Questions 1. Will the inmates be required to shower at a specific time? • No 2. Will all the cell pods release their inmates for showering within the same hour? • Yes. (This means that the design must accommodate a 1-h recovery period.) 3. Will the shower duration per inmate be limited? • Yes, to 7 min per inmate, with 3.5 min of water usage 4. Does the facility anticipate double bunking inmates, either now or in the future? • No Calculations for Jail Housing Units The ratio of 140 to 50°F (60 to 10°C) water flowing at the shower can be calculated using the mixed-water formula, Equation 1.7, from Chapter 1: American Corrections Association, Adult Corrections Institutions, 3d ed. Ibid.

1 2

Sept/Oct 2005 • Plumbing Systems & Design

57

Continuing Education: Jail and Prison Housing Units Simpo PDF Merge and - http://www.simpopdf.com (T –Split Tc) Unregistered Versionsized to handle approximately 50% of the shower demand P= m where P = Tm = Th = Tc =

(Th – Tc)

Percentage of mixture that is hot water Temperature of mixed water = 105°F (41°C) Temperature of hot water = 140°F (60°C) Temperature of cold water = 50°F (10°C) – 50 55 P = 105 140 – 50 = 90 = 0.61 – 10 31 P = 41 60 – 10 = 50 = 0.61

[

]

With each shower flowing 2.5 gpm (0.13 L/sec), 2.5 gpm × 0.61 = 1.53 gpm will be 140°F hot water (0.13 L/sec • 0.61 = 0.08 L/sec will be 60°C hot water) 8 inmates × 3.5 min = 28 min of water flowing per shower during the peak hour 6 pods × 3 showers per pod = 18 showers total 18 showers × 28 min = 504 min 504 min × 1.53 gpm = 771.12 gal 140°F hot water per peak hour demand (504 min • 0.10 L/sec • 60 sec/min = 3024 L 60°C hot water per peak hour demand) At this time a judgment will have to be made by the designer as to whether or not the auxiliary equipment will be operating during the peak hour. For this example, we will assume it will not.

Auxiliary Equipment Demand Door type dishwasher with internal heater = 69 gph (261.17 L/h) Single compartment sink = 30 gph (113.55 L/h) Clothes washing machines, 1 per pod × 6 pods = 6 6 × 2 loads @ 20 gal/load = 240 gph (6 • 2 loads @ 75.7 L/load = 908.40 L/h) Auxiliary equipment demand for 140°F water = 339 gph (Auxiliary equipment demand for 60°C water = 1283.12 L/h) Assuming that operation of the auxiliary equipment does not coincide with the peak hour demand, sizing the heater and storage tank to handle the additional load will not be necessary. The heater size required for inmate showering is more than twice the size needed for the auxiliary equipment demand. Recommendation Heater sizing Two heaters should be selected, each sized to serve between 60 and 100% of the total demand. In prison housing units some redundancy in the water heating system is necessary. The level of redundancy should be discussed with the facility’s owners. Storage tank sizing If the water heater is sized to meet the recovery required to handle the peak shower demand, the storage tank may be

during the period of peak use. The storage tank should be large enough to prevent the heater from cycling on and off more than four times per hour during off-peak hours. This requirement necessitates finding a balance between excessive tank size and short cycling. Calculation 771.12 gph × 0.50 = 385.6 gal (2.93 m3/h • 0.50 = 1.47 m3/h) 385.6 = 481.6 gal storage tank size 0.80 1470 L = 1837.5 L storage tank size 0.80

[

]

The auxiliary equipment demand of 339 gph (1283.12 L/h) will have the greatest influence on the amount of cycling done by the heater during off-peak hours. 339 gph = 5.56 gpm average flow of 140°F water 60 1283.12 L/h = 0.36 L/sec average flow of 60°C water 60 • 60 5.56 gpm × 15 min = 83.4 gal

[

]

(0.36 L/sec • 60 sec/min • 15 min = 324 L) 83.4 = 104.25 gal storage 0.80 324 L = 405 L storage 0.80

[

]

The selected size of a 481.6-gal (1837.5-L) storage tank is more than adequate to meet this demand. PRISON EXAMPLE This is an example of a housing facility for 384 inmates. It has four wings (96 inmates per wing) and each wing has four stories (24 inmates per wing per story). A central kitchen and laundry are located in a separate building. Shower areas are provided on every floor of every wing, and each of these areas has three shower heads. Design Criteria and Assumptions 1. Inmate lavatories and showers will be supplied with 105°F (41°C) circulated hot water. Showers are to have 2.5 gpm (0.16 L/sec) flow restrictors and lavatories 2.0 gpm (0.13 L/sec) flow restrictors. 2. There will be separate systems for the kitchen and laundry areas. 3. The water temperature for the laundry area will be 180°F (82°C) and for the kitchen area 140°F (60°C), plus there will be a separate loop of 105°F (41°C) water for the hand washing lavatories and toilets located in the kitchen area . 4. Water at 140°F (60°C) will be supplied to the dishwasher. The dishwasher will have a separate booster heater to raise water temperature to the 180°F (82°C) required for the final rinse cycle. 5. The storage tank capacity varies considerably—from 0% for instantaneous heaters to more than100%. Check

Reprinted from Domestic Water Heating Design Manual, 2nd ed. 2003. Chicago: American Society of Plumbing Engineers. Chapter 9, “Jail and Prison Housing Units” (pp. 179-188). © 2003, American Society of Plumbing Engineers.

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Plumbing Systems & Design • Sept/Oct 2005


to determine if the owner has a preference. Remember, most owners already operate existing jails or prisons; they may have established design parameters. The initial cost of equipment, the unit performance, and operating costs are also factors to be considered when sizing the storage tank. 6. Look for additional support facilities, such as the barber shop, pantries, or an emergency medical clinic. 7. Although operating hours for the laundry area are generally from 8:00 A.M. to 5:00 P.M., review operational times and schedules with the owner. 8. Sources of heat: The selection of steam, natural gas, or electricity will have an enormous impact on the type of heater and on energy consumption. Note: A central steam generation plant may favor an instan-taneous type steam-to-hot-water converter with minimum hot water storage for surges. Remember, redun dancy in heaters is always required for jails and prisons to allow for problems created by inmates. The cost of generating and distributing steam is also a factor to be consid ered. 9. The method to use for sizing the water heater and storage tank may be determined by the owner/operator of the facility. 10. One inmate per cell equals 384 inmates. A question that should be asked is whether the owner plans to expand in the future by putting more than one inmate in each cell. Questions 1. Will the inmates be required to shower at a specific time? • No 2. Will the shower duration per inmate be limited or do inmates have control over when they shower? • Showers are limited to 7 min per inmate, with 3.5 min of water usage per shower. 3. Will all of the cell pods release their inmates for showering within the same hour? • Yes. (This means that the design must accommodate a 1-h recovery period.) 4. Does the facility anticipate double bunking the inmates now or in the future? • No 5. Does the facility have a work-release program? • Yes 6. What is the time allocated for the work-release inmates to shower prior to leaving for their duties in the work– release program? • One hour, at the same approximate time as the other inmates. Calculations for Inmate Housing Units Refer to the calculations done for the jail example for the methodology for determining the 1.53 gpm (0.1 L/sec) flow per shower head and the operation time of 28 min per shower. 48 showers × 28 min = 1344 min

1344 min × 1.53 gpm = 2056 gal of 140°F hot water for peak hour demand (1344 min • 0.096 L/sec • 60 sec/min = 7741.44 L/h of 60°C hot water for peak hour demand)

Storage Tank Sizing In this example, inmate lavatories will have the only impact on tank sizing because the kitchen and laundry will have separate systems. If the water heater is sized to meet the recovery required to handle the peak shower demand, the storage tank may be sized to handle approximately 50% of the shower demand during the period of peak use. The storage tank should be large enough to prevent the heater from cycling on and off more than four times per hour during off-peak hours. This requirement necessitates finding a balance between excessive tank size and short cycling. Calculation 2056 gph × 0.50 = 1028 gal 140°F hot water (7.74 m3/h • 0.50 = 3.87 m3 60°C hot water) 1028 gal = 1285 gal storage tank size 0.80 eff. 3870 L = 4837.5 L storage tank size [ 0.80 ] eff. Kitchen Considerations 1. The item that has the greatest effect on hot water demand is the dishwasher. Some central kitchens do not have dining areas, in which case all meals are shipped to the housing units in bulk for distribution and the dishwashers are in the housing units. 2. The temperature of the hot water going to kitchen lavatories should not exceed 110°F (43°C) for safety reasons. 3. Check to see if the dishwasher has a booster heater and determine the type of energy used (steam or electricity). This information will help you decide whether or not to generate 180°F (82°C) water. Note: Some dishwashers on the market use chemicals for disinfecting, thus the higher water temperature is not required. 4. After dishwashers, compartment sinks are the next largest user of 140°F (60°C) hot water. The higher temperature is required to cut through grease on pots and pans. Some three-compartment sinks have booster heaters in the rinse tank to maintain the higher temperature. 5. Other kitchen items that use hot water are the prerinse for the dishwasher, the vegetable sinks, and the cart washdown hose bibs. 6. Always check the kitchen consultant’s plans for hot water requirements. 7. Refer to the “Hospitals” chapter for additional information on kitchens. Laundry Considerations 1. Review the laundry consultant’s plans and determine the type of washing machine/extractor used. Prison laundries are similar to hospital laundries in that they process sheets, pillow cases, and uniforms. The size and number Sept/Oct 2005 • Plumbing Systems & Design

59

Continuing Education: Jail and Prison Housing Units Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com of machines are normally decided by the owner or the consultant. 2. Inmates each generate about 30 lb (13.61 kg) of laundry a week. This consists of 1 pillowcase, 2 sheets, 1 towel, and uniforms. 3. Additionally, prison laundries usually handle the uniforms of the correctional officers. 4. Sometimes prison laundries do laundry for outside hospitals as a prison industry. 5. Consider the feasibility of a heat recovery system that uses the wash-water discharge. The laundry consultant can probably advise you about this. 6. Laundry equipment suppliers are the only reliable source of information on the hot water demands and required temperaures of their washers. They can tell you how many gallons (liters) of water the machines require and the maximum number of cycles per hour they will operate. 7. Washers demand their hot water fast. It is not unusual for a 2-in. (DN50) hot water line to be connected to the larger

60


washers. Therefore, larger than normal storage capacity is needed to handle the surges in hot water demand. One rule of thumb is to provide 75% of the maximum hourly demand in storage; don’t provide less than 50% of that amount. 8. In 1992 a new federal law (“Bloodborne Pathogen”) was passed to protect workers against the human immunodeficiency virus (HIV) and hepatitis B virus (HBV). All detention facilities are now under this new federal regulation. A major/critical new standard was created by the law: “When an officer’s uniform becomes contaminated with blood products, the officer cannot leave his workplace with the uniform on. The facility must clean that uniform and reissue it to the officer.” The law states further that “inmate labor cannot be used when handling blood contaminated items.” A washer and dryer for the aforementioned are required to achieve compliance with the law. They should be located in a space that is under the direct supervision of an officer so the security of the officers’ uniforms will not be jeopardized. n


Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson, Chicago Chapter President Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PSD), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status. ASPE features a technical article in every issue of PSD, excerpted from its own publications. Each article is followed by a multiplechoice test and a simple reporting form. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of

90% or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years. No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PSD within the past 12 months. However, CEU credit only can be obtained on a total of eight PSD articles in a 12-month period. Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

CE Questions—“Jail and Prison Housing Units” (PSD 129) 1. The sizing of a domestic water storage tank shall be large enough to prevent the water heaters from cycling no more than ____________ times per hour during off-peak hours. a. two b. four c. six d. eight 2. What are some of the most important factors to consider when sizing a domestic hot water storage tank? a. operating costs b. initial costs c. unit performance d. all of the above 3. The American Corrections Association ____________. a. has established the hot water requirements for jails and prisons b. requires the temperature of the hot water at inmate showers be between 100oF and 110oF c. has established the generally used standard of 105oF for inmate showers d. requires the use of push button type showers

7. Each inmate generates approximately ____________ pounds of laundry per week. a. 10 b. 20 c. 30 d. 40 8. In what year was the Bloodborne Pathogen law passed that was intended to protect workers against human immunodeficiency virus (HIV) and the hepatitis B virus (HBV)? a. 1986 b. 1992 c. 1998 d. 2004 9. Auxiliary equipment demand ____________. a. must be included in the water heating sizing b. must be assumed to not be in operation during the shower period c. should be determined whether or not it will be operating during the peak hour d. is equal to 69 gallons per hour

4. A typical hot water delivered temperature for inmate lavatories is ____________oF. a. 95 b. 100 c. 105 d. 110

10. The item of kitchen equipment that has the greatest effect on the hot water demand is the ____________. a. vegetable prep sink b. triple pot sink c. dishwasher d. exhaust hood washdown system

5. If the water heater is sized to meet the recovery required to handle the peak shower demand of a jail housing unit, ____________. a. the storage tank may be sized to handle approximately 50% of the shower demand b. the storage tank should be large enough to prevent the heater from cycling on and off more than four times per hour during off-peak hours c. the storage tank should be 481.6 gallons d. both a and b

11. A jail housing pod of 20 cells, each with one inmate, would require how many showers? a. one per cell b. three c. four d. the number is determined by the architect

6. The main factor to consider in sizing a water heating system for a jail is ____________. a. showers b. the many lavatories in housing units c. the temperature of the hot water to be provided and the duration of the peak flow d. the efficiency of the storage system

12. The objective of this chapter is ____________. a. to help government authorities determine how the building will operate b. to help the designer understand and deal with the problems of designing water heating systems for jail and prison housing units c. to help the designer understand and deal with the problems of designing water heating equipment for jail and prison housing units

d. all of the above

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Continuing Education Application Form 1. Make a photocopy of this form. Leaving this page in PSD allows others to use it to obtain continuing education units (CEUs). 2. PRINT your name and address. Be sure to place your membership number in the appropriate space. This form is valid up to 1 year from date of publication. The PSD continuing education unit program is approved by ASPE for up to 1 contact hour (0.1 CEU) of credit per article studied. 3. Answer the multiple-choice continuing education (CE) questions (found after each CE article) and the appraisal questions on this page. 4. Submit this form and the answer sheet below, with the payment of the appropriate fee by check or money order made payable to ASPE, or submit the credit card information to ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656–1116. 5. Participants who earn a passing score (90%) on the CE questions will receive a letter of certification within 30 days of PSD’s receipt of the application (no special certificates will be issued). (CEU information will be retained on the ASPE Database.) Participants who wish to retake the test should submit their retest along with an additional fee—$25 for an ASPE member (currently waived) or $35 for a nonmember. Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________ I am applying for the following continuing education credits:




Signature Expiration date: Continuing education credit will be given for this examination through September 30, 2006. Applications received after that date will not be processed.

PSD Continuing Education Answer Sheet


Signature

Jail and Prison Housing Units (PSD 129)

Questions appear on page 61. Circle the answer to each question. Q 1. A B C D Q 2. A B C D Q 3. A B C D Q 4. A B C D Q 5. A B C D Q 6. A B C D Q 7. A B C D Q 8. A B C D Q 9. A B C D Q 10. A B C D Q 11. A B C D Q 12. A B C D 62



Expiration date



Jail and Prison Housing Units (PSD 129) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

Life-Safety Systems

PSD 134



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CONTINUING EDUCATION Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com

Life-Safety Systems

Introduction A threat to personnel safety often present in pharmaceutical facilities is accidental exposure and possible contact with toxic gases, liquids, and solids. This chapter describes water-based emergency drench equipment and systems commonly used as a first-aid measure to mitigate the effects of such an accident, Also described are the breathing-air systems that supply air to personnel for escape and protection when they are exposed to either a toxic environment resulting from an accident or normal working conditions that make breathing the ambient air hazardous.

Emergency Drench-Equipment Systems General When toxic or corrosive chemicals come in contact with the eyes, face, and body, flushing with water for 15 min with the clothing removed is the most recommended first-aid action that can be taken by nonmedical personnel prior to medical treatment. Emergency drench equipment is intended to provide a sufficient volume of water to effectively reach any area of the body exposed to or has come into direct contact with any injurious material. Within facilities, specially designed emergency drench equipment, such as showers, drench hoses, and eye and face washes, are located adjacent to all such hazards. Although the need to protect personnel is the same for any facility, specific requirements differ widely because of architectural, aesthetic, location, and space constraints necessary for various industrial and laboratory installations. System Classifications Drench equipment is classified into two general types of system based on the source of water. These are plumbed systems, which are connected to a permanent water supply, and self-contained or portable equipment, which contains its own water supply. Self-contained systems can be either gravity feed or pressurized. One type of self-contained eyewash unit is available that does not meet code requirements for storage or delivery flow rate. This is called the personnel eyewash station and is selected only to supplement, not replace, a standard eyewash unit. It consists of a solution-filled bottle(s) in a small cabinet. This cabinet is small enough to be installed immediately adjacent to a high hazard. If an accident occurs, the bottle containing the solution is removed and used without delay to flush the eyes while waiting for the arrival of trained personnel and during travel to a code-approved eyewash or first-aid station. Codes and Standards 1. ANSI Z-358.1, Emergency Shower and Eyewash Equipment. 2. OSHA has various regulations for specific industries pertaining to the location and other criteria for emergency eyewashes and showers.

3. The Safety Equipment Institute (SEI) certifies that equipment meets ANSI standards. 4. Applicable plumbing codes. For the purposes of the discussion in this section on drench equipment, the word “code” shall refer to ANSI Z-358.1. Types of Drench Equipment Emergency drench equipment consists of showers, eyewash units, face-wash units, and drench hoses, along with interconnecting piping and alarms if required. All of these units are available either singly or in combination with each other. Ancillary components include thermostatic mixing systems, freeze protection systems and enclosures. Each piece of equipment is designed to perform a specific function. One piece is not intended to be a substitute for another, but rather, to complement the others by providing additional availability of water to specific areas of the body as required. Emergency Showers Plumbed Showers Plumbed emergency showers are permanently connected to the potable water piping and designed to continuously supply enough water to drench the entire body. A unit consists of a large-diameter shower head intended to distribute water over a large area. The most commonly used type has a control valve with a handle extending down from the valve on a chain or rod that is used to turn the water on and off manually. Code requires the shower be capable of delivering a minimum of 30 gpm (113.6 L/min) of evenly dispersed water at a velocity low enough so as not to be injurious to the user. Where this flow rate is not available, 20 gpm (75.7 L/min) is acceptable if the shower-head manufacturer can show the same spray pattern required for 30 gpm can be achieved at the lower flow rate. The minimum spray pattern shall have a diameter of 20 in. (58.8 cm), measured at 60 in. (152.4 cm) above the surface on which the user stands. This requires a minimum pressure of approximately 30 psi (4.47 kPa). Emergency showers can be ceiling mounted, wall mounted or floor mounted on a pipe stand, with the center of the spray at least 16 in. (40.6 cm) from any obstruction. Showers should be chosen for the following reasons: 1. When large volumes of potentially dangerous materials are present. 2. Where a small volume of material could result in large affected areas, such as in laboratories and schools. A typical emergency shower head mounted in a hung ceiling is illustrated in Figure 1. Self-Contained Showers Self-contained emergency showers have a storage tank for water. Often this water is heated. The shower shall be capable of delivering a minimum of 20 gpm (75.5 L/min) for 15 min. The requirements for mounting height and spray pattern are the same as they are for plumbed showers.

Reprinted from Pharmaceutical Facilities Plumbing Systems, Chapter 8: “Life-Safety Systems,” by Michael Frankel. © American Society of Plumbing Engineers. Plumbing Systems & Design

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Figure 1 TypicalPDF Emergency Showerand Simpo Merge

Emergency Face Wash

Split Unregistered Version - http://www.simpopdf.com The face wash is an enhanced version of the eyewash. It has the same design requirements and configuration, except the spray heads are specifically designed to deliver a larger water pattern and volume will flush the whole face and not just the eyes. The face wash should deliver approximately 8 gpm (55 L/min). The stream configuration is illustrated in Figure 2. Very often, the face wash is chosen for combination units. In general, the face wash is more desirable than the eyewash because it is very likely an accident will affect more than just the eyes. All dimensions and requirements of the free-standing face wash are similar to those for the eyewash. Drench Hoses A drench hose is a single-head unit connected to a water supply with a flexible hose. The head is generally the same size as a single head found on an eye/ face wash. Code requires the drench hose be capable of delivering a minimum of 0.4 gpm (1.5 L/min). It is controlled either by a squeeze handle near the head or a push-plate ball valve located at the connection to the water source. It is used as a supplement to showers and eye/face washes to irrigate specific areas of the body. Drench hoses are selected for the following reasons: 1. To spot drench a specific area of the body when the large volume of water delivered by a shower is not called for. 2. To allow irrigation of an unconscious person or a victim who is unable to stand. 3. To irrigate under clothing prior to the clothing’s removal.

Emergency Eyewash Plumbed Eyewash Emergency eyewashes are specifically designed to irrigate and flush both eyes simultaneously with dual streams of water. The unit consists of dual heads in the shape of a “U,” each specifically designed to deliver a narrow stream of water, and a valve usually controlled by a large push plate. Code requires the eyewash to be capable of delivering a minimum of 0.4 gpm (1.5 L/min). Many eyewashes of recent manufacture deliver approximately 3 gpm (11.4 L/min). Once started, the flow must be continuous and designed to operate without the use of the hands, which shall be free to hold open the eyelids. The flow of water must be soft to avoid additional injury to sensitive tissue. To protect against airborne contaminants, each dual stream head must be pro- Figure 2 Combination Emergency Shower, Eye/Face Wash, and Drench Hose Unit tected with a cover that is automatically discarded when the unit is activated. The head covers shall be attached to the heads by a chain to keep them from being lost. The eyewash can be mounted on a counter or wall, or as a free stranding unit attached to the floor. The eyewash could be provided with a bowl. The bowl does not increase the efficiency or usefulness of the unit but aids in identification by personnel. It is common practice to mount a swivel type eyewash on a laboratory sink faucet, installed so it can be swung out of the way during normal use of the sink but can be swung over the sink bowl in order to be operated in an emergency. The code recommends (but does not require) the use of a buffered saline solution to wash the eyes. This could be accomplished with a separate dispenser filled with concentrate that will introduce the proper solution into the water supply prior to reaching the device head. A commonly used device is a wallmounted, 5 to 6-gal (20 to 24-L) capacity solution tank connected to the water inlet dispenses a measured amount of solution when flow to the eyewash is activated. A backflow device shall be installed on the water supply. Self-Contained Eyewash A typical self-contained eyewash has a storage tank with a minimum 15-min water supply. The mounting height and spray pattern requirements are the same as those for a plumbed eyewash. JULY/AUGUST 2006


CONTINUING EDUCATION: Life-Safety Systems shower and eyewash that is handicapped accessible using handles Combination Equipment Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Combination equipment consists of multiple-use units with a hung from the ceiling is illustrated in Figure 3. The handle must common water supply and supporting frame. Combinations are be located close enough to the center of the shower to be easily available that consist of a shower, eye/face wash, and drench reached, which is about 2 ft 0 in. from the center of the shower. hose in any configuration. The reason for the use of combina- Alarms tion equipment is usually economy, but the selection should Alarms are often installed to alert security or other rescue perbe made considering the type of irrigation appropriate for the sonnel that emergency drench equipment has been operated potential injuries at a specific location. For combination units, and to guide them rapidly to the scene of the accident. Comthe water supply must be larger, capable of delivering the flow monly used alarms are audible and visual devices—such as rate of water required to satisfy two devices concurrently rather flashing or rotating lights on top of, or adjacent to, a shower than only a single device. or eyewash—and electronic alarms wired to a remote security The most often-used combination is the drench shower and panel. Remote areas of a plant are particularly at risk if personface wash. Figure 2 illustrates a combination shower, eye/face nel often work alone. Alarms are most often operated by a flow wash and drench hose complete with mounting heights. switch activated by the flow of water when a piece of equipment Drench Equipment Components Controls Often referred to as “activation devices,” controls cause water to flow at an individual device. Stay-open valves are required by code in order to leave the hands free for the removal of clothing or for holding eyelids open. The valves most often used are ball valves with handles modified to provide for the attachment of chains, rods, and push plates. In very limited situations, such as in schools, valves that automatically close (quick-closing) are permitted if they are acceptable to the facility and authorities having jurisdiction. Valves are operated by different means to suit the specific hazard, location, durability, and visibility requirements. The operators on valves are handles attached to pull rods, push plates, foot-operated treadle plates and triangles. A solid pull rod is often installed on concealed showers in order to push the valve closed after operation. Another method is to have two handles attached to chains that extend below the hung ceiling, one to turn on the valve and another handle to turn it off. Chains are used if the handle might be accidentally struck, they enable the handle to move freely and not injure the individual who might accidentally strike the hanging operator. Operating handles for the physically challenged are mounted lower than those for a standard unit. In many cases, this requires that operating handles be placed near walls to keep them out of traffic patterns where they would be an obstruction to ablebodied people passing under them. A free-standing combination Figure 3 Clearance Dimensions Around Shower and Eye/Face Wash


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is used. When tempered water systems are used to supply drench equipment, a low water temperature of 60°F shall cause an alarm annunciation. Flow-Control Device Where water pressure exceeds 80 psig (550 kPa) or if the difference in water pressure between the first and last shower head is more than 20 psig (140 kPa), it is recommended that a selfadjusting flow-control device be installed in the water-supply pipe. Its purpose is to limit the flow to just above the minimum required by the specific manufacturer for proper functioning of equipment. Such devices are considered important because a shower installed at the beginning of a long run has a much greater flow than the device at the end. During operation, the higher pressure could cause the flow rate to be as much as 50 gpm (L/min). If no floor drain is provided, the higher flow for 15 min at the higher pressure could produce a much greater amount of water that must be cleaned up and disposed of afterwards. Drench hoses and eye and face washes are not affected because of their lower flow rates and their flow head designs. Where pressure-reducing devices are required for an entire system, they should be set to provide approximately 50 psig (345 kPa). System Design General It is a requirement that a plumbed system be connected to a potable water supply as the sole source of water. This system is therefore subject to filing with a plumbing or other code official for approval and inspection of the completed facility, as are standard plumbing systems. An adequately sized pipe with sufficient pressure must be provided from the water supply to meet system and device operating-pressure requirements for satisfactory functioning. One maintenance requirement is that the water in the piping system be flushed to avoid bacterial growth. It is common practice to add antibacterial and saline products to a self-contained eyewash unit and an antibacterial additive to an emergency shower. Water is also commonly used if it can be changed every week. It is well established that no preservative will inhibit bacterial growth for an extended period of time. Selfcontained equipment must be checked regularly to determine if the quality of the stored water has deteriorated to a point where it is not effective or safe to use. If valves are placed in the piping network for maintenance purposes, they should be made for unauthorized shut-off. PSDMAGAZINE.ORG

Appropriate pressure loss calculations should be made to ensure Water-Supply Pressure and Flow Rates Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Emergency showers require between 20 and 30 gpm (76 to 111 the hydraulically most remote unit is supplied with adequate L/min), with 30 gpm recommended. The minimum pressure pressure with the size selected. Adjust sizes accordingly to meet required is 30 psig (4.5 kPa) at the farthest unit, with a generally friction loss requirements. The pipe material should be copper to minimize clogging the accepted maximum pressure of 70 psi (485 kPa). Code mentions a high pressure of 90 psig (612 kPa), which is generally consid- heads of the units in time with the inevitable corrosion products ered to be excessive. Most plumbing codes do not permit water released by steel pipe. Plastic pipe (PVC) should be considered pressures as high as 90 psig. Generally accepted practice limits where excessive heat and the use of closely located supports will the high water pressure to between 70 and 80 psig (480 and 620 not permit the pipe to creep in time. Emergency drench equipment shall be sized based on the kPa). Most eyewash units require a minimum operating pressure single highest flow rate, usually 30 gpm (115 L/min) for an of 15 psig (105 kPa) with a flow rate minimum of 3 gpm (12 L/ emergency shower. Piping is usually a 1¼-in. header of copper min) at the farthest unit. Maximum pressure is similar to that pipe for the entire length of a plumbed system. for showers. Face washes and drench hoses require a minimum Flushing Water Disposal operating pressure of 15 psig (105 kPa) with a minimum flow Water from emergency drench equipment is mainly discharged rate of 8 gpm (30 L/min) at the farthest unit. onto the floor. Individual eye/face washes mounted on sinks System Selection

Plumbed System

The advantages of a plumbed system include:

1. Permanent connection to a fresh supply of water, requiring no maintenance and only minimum testing of the devices to ensure proper operation. 2. It provides an unlimited supply of water often at larger volumes than self-contained units. Disadvantages include: 1. Higher first cost than a self-contained system. 2. Maintenance is intensive. Such systems require weekly flushing, often into a bucket, to remove stagnant water in the piping system and replace it with fresh water. Self-Contained System

Advantages of the self-contained system include:

1. Lower first cost compared to a plumbed system. 2. Can be filled with a buffered, saline solution, which is recommended for washing eyes. 3. Available with a container to catch waste water. 4. Portable units can be moved to areas of greatest hazard with little difficulty. 5. A gravity eyewash is more reliable. The water supply can be installed where there is room above the unit. If not, a pressurized unit mounted remotely should be selected. Disadvantages include: 1. Only a limited supply of water at a lesser flow rate is available. 2. The stored liquid must be changed on a regular basis to maintain purity. The plumbed system is the type of system selected most often because of the unlimited water supply. Pipe Sizing and Material In order to supply the required flow rate to a shower, a minimum pipe size of 1 in. (25 mm) is required by code, with 1¼ in. (30 mm) recommended. If the device is a combination unit, a 1¼-in. size should be considered as minimum. An emergency eye/face wash requires a minimum ½ in. (13 mm) pipe size. Except in rare cases where multiple units are intended to be used at once, the piping system size should be based on only one unit operating. The entire piping system is usually a single size pipe based on the requirements of the most remote fixture.

discharge most of the water into the adjacent sink. Combination units have an attached eye/face wash also discharge water on the floor. There are different methods of disposing of the water resulting from an emergency device depending on the facility. The basic consideration is whether to provide a floor drain adjacent to a device to route that water from the floor to a drainage system. It is accepted practice not to provide a floor drain at an emergency shower. Experience has shown in most cases, particularly in schools and laboratories, it is easier to mop up water from the floor in the rare instances emergency devices are used rather than add the extra cost of a floor drain, piping and a trap primer. Considerations include: 1. If the drain is not in an area where frequent cleaning is done, the trap may dry out, allowing odors to be emitted. 2. Is there an available drainage line in the area of the device? 3. Can the chemical, even in a diluted state, be released into the sanitary sewer system or must it be routed to a chemical waste system for treatment? 4. Must purification equipment be specially purchased for this purpose? Installation Requirements for Drench Equipment The need to provide emergency drench equipment is determined by an analysis of the hazard by design professionals or health or safety personnel and by the use of common sense in conformance with OSHA, CFR, and other regulations for specific occupations. Judgment is necessary in the selection and location of equipment. Very often, facility owners have specific regulations for its need and location. Dimensional Requirements The mounting height of all equipment, as illustrated in ANSI Z358.1, is shown in Figure 2. If the shower head is free-standing, the generally accepted dimension for the mounting height is 7 ft 0 in. (2.17 m) above the floor. Generally accepted clearance around showers and eye/face washes is illustrated in Figure 3. A wheelchair-accessible, free-standing, combination unit is illustrated in Figure 4. Equipment Location The location of the emergency drench equipment is crucial to the immediate and successful first-aid treatment of an accident victim. It should be located as close to the potential hazard as is practical without being affected by the hazard itself or potential accidental conditions, such as a large release or spray of chemiJULY/AUGUST 2006


CONTINUING EDUCATION: Life-Safety Systems Figure 4 Wheelchair-Accessible Shower Eyewash Equipment Simpo PDF Merge andandSplit Unregistered

Traveling through rooms that may have locked doors to

Version - http://www.simpopdf.com reach equipment shall be avoided, except placing emergency showers in a common corridor, such as outside individual laboratory rooms, is accepted practice. Care should be taken to avoid locating the shower in the path of the swinging door to the protected room to prevent personnel coming to the aid of the victims from knocking them over. Emergency eye/face washes should be located close to the potential source of hazard. In laboratories, accepted practice is to have 1 sink in a room fitted with an eyewash on the counter adjacent to the sink. The sink cold-water supply provides water to the unit. The eyewash could be designed to swing out of the way of the sink if desired. Visibility of Devices High visibility must be considered in the selection of any device. The recognition methods usually selected are high-visibility signs mounted at or on the device; having the surrounding floors and walls painted a contrasting, bright color; and having the device in a bright, well lit area on the plant floor to help a victim identify the area and help in first-aid activities.

cals resulting from an explosion or a pipe and tank rupture. Another location problem is placement adjacent to electrical equipment. Location on normal access and egress paths in the work area will reinforce the location to personnel, who will see it each time they pass. There are no requirements in any code pertaining to the location of any drench equipment in terms of specific, definitive dimensions. ANSI code Z-358.1 requires emergency showers be located a maximum distance of either 10 seconds travel time by an individual or no more than 75 ft (22.5 m) from the potential protected hazard, whichever is shorter. If strong acid or caustic is used, the equipment should be located within 10 ft (3 m) of the potential source of the hazard. The path to the unit from the hazard shall be clear and unobstructed, so impaired sight or panic will not prevent clear identification and access. There is no regulation as to what distance could be covered by an individual in 10 seconds. There are also no specific provisions for the physically challenged. Since there are no specific code requirements for locating drench equipment, good judgment is required. Accepted practice is to have the equipment accessible from three sides. Anything less generally creates a “tunnel” effect that makes it more difficult for the victim to reach the equipment. It should be located on the same level as the potential hazard when possible. Plumbing Systems & Design

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Number of Stations The number of drench-equipment devices provided in a facility is a function of the number of people in rooms and areas with potential exposure to any particular hazard at any one time, based on a worst-case scenario. It is rare for more than one combination unit to be installed. It is important to consider if a group of individuals has potential exposure to a specific hazard, more than one drench unit may be required. Consulting with the end user and the safety officer will provide a good basis for the selection of the type and number of equipment. Generally, one shower can be provided between an adjacent pair of laboratories, with emergency eye/face washes located inside each individual laboratory. In open areas, it is common practice to locate emergency equipment adjacent to columns for support. Water Temperature Code now requires tempered water of approximately 85°F be supplied to equipment. A comfortable range of 60 to 95°F (15 to 35°C) is mentioned in the code. For most indoor applications, this temperature range is achieved because the interior of a facility is heated in the winter and cooled in the summer to approximately 70°F (20° C). Since the water in the emergency drench system is stagnant, it assumes the temperature of the ambient air. A generally accepted temperature of between 80 and 85°F (27 and 30°C) has been established as a “comfort zone” and is now the recommended water temperature. The body will attempt to generate body heat lost if the drenching fluid is at a temperature below the comfort zone. The common effect is shivering and increased heart rate. In fact, most individuals are uncomfortable taking a shower with water at about 60°F (15°C). With the trauma induced by an accident, the effect is escalated. Another consideration is the potential chemical reaction and/or acceleration of reaction with flushing water or water at PSDMAGAZINE.ORG

a particular temperature. Where the hazard is a solid, such as the respirator. The most common operating range for systems is Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com radioactive particles, that can enter the body through the pores, between 90 and 110 psig (620 and 760 kPa). a cold-water shower shall be used in spite of its being uncomMuch of the equipment used in the generation, treatment, fortable. It is necessary to obtain the opinions of medical and and distribution of compressed air for breathing-air systems is hygiene personnel where any doubt exists about the correct use common to that for medical/surgical air discussed in the “Comof water or water temperature in specific facilities. pressed-Gas Systems” chapter. Where showers are installed outdoors, or indoors where heatCodes and Standards ing is not provided, the water supplying the showers must be 1. OSHA: 29 CFR 1910. tempered if the air temperature is low. Manufacturers offer a 2. CGA: commodity specifications G-7 and G-7.1. variety of tempering methods, including water-temperature 3. Canadian Standards Association (CSA). maintenance cable similar to that used for domestic hot-water 4. National Institute of Occupational Safety and Health systems for this purpose and mixing valves with hot and cold(NIOSH). water connections. In remote locations, complete self-contained 5. Mine Safety and Health Act (MSHA). units are available with storage tanks holding and maintaining 6. NFPA: NFPA-99, Medical Compressed Air. heated water. 7. DOD (Department of Defense): Where applicable. Protection Against Temperature Extremes 8. ANSI: Z-88.2, Standard for Respiratory Protection. In areas where freezing is possible and water drench equipment 9. Code of Federal Regulations (CFR). is connected to an above-ground, plumbed water supply, freeze protection is required. This is most often accomplished by using Breathing-Air Purity electric heating cable and providing insulation around the Air for breathing purposes supplied from a compressor or a entire water-supply pipe and the unit itself. It is recommended pressurized tank must comply, as a minimum, with quality the water temperature be maintained at 85°F (20°C). verification level grade D in CGA G-7.1 (ANSI Z-86.1). Table 1, For exterior showers located where freezing is possible, the from ANSI/CGA G-7.1, lists the maximum contaminant levels water supply shall be installed below the frost line and a freeze- for various grades of air. proof shower shall be installed. This type of shower has a method For grade D quality air, individual limits exist for condensed of draining the water above the frost line when the water to the hydrocarbons, carbon monoxide, and carbon dioxide. Particudrench equipment is turned off. When a number of drench-equipment Table 1 Maximum Contaminant Levels for Various Grades of Air (in ppm [mole / mole] unless shown otherwise) devices are located where low temperature is common, a circulating tempered-water supply Limiting Characteristics A K L D E G J M N should be considered. This uses a water heater atm / atm / atm / atm / atm / atm / atm / atm / atm / and a circulating pump to supply the drench Percent O2 balancea 19.5 - 19.5 - 19.5 - 19.5 - 20 - 19.5 - 19.5 - 19.5 - 19.5 23.5 23.5 23.5 23.5 22 23.5 23.5 23.5 23.5 equipment. The heater shall be capable of gen- predominantly N2b Water, ppm (v / v) 200 50 1 3 erating water from 40 to 80°F at a rate of 30 gpm Dew point, °F b -33 -54 -104 -92 (or more if more than one shower could oper- Oil (condensed) (mg / m3 ate simultaneously). at NTP) 5c 5c Noned e,f Carbon monoxid 10 10 5 1 1 10 In areas where the temperature may get too None high, it is accepted practice to insulate the Odor f Carbon dioxide 1000 500 500 0.5 1 500 water-supply piping. Total hydrocarbon content (as methane) 25 25 15 0.5 1 Breathing-Air Systems Nitrogen dioxide Nitric 2.5 0.1 0.5 2.5 oxide General Sulfur dioxide 2.5 0.1 5 Breathing-air systems supply air of a specific Halogenated Solvents 10 0.1 minimum purity to personnel for purposes Acetylene 0.05 of escape and protection after exposure to Nitrous oxide 0.1 a toxic environment resulting from an acci- USP Yes dent or during normal work where conditions Source: ANSI / CGA G-7.1.ANSI 2-86.1, Table 1. make breathing the ambient air dangerous. Note: The 1973 edition of CGA G-7.1 listed nine quality verification levels of gaseous air, lettered A to J, and two quality verification levels As defined by 30 CFR 10, a toxic environment of liquid air, lettered A and B. Some of those letter designations were dropped from the 1989 edition, since they no longer represent major has air that “may produce physical discomfort volume usage by industry. Four new letter designations, K, L, M, and N, have been added to reflect current specifications. To get a listing of immediately, chronic poisoning after repeated quality verification levels dropped, see CGA-7-1-1973 or contact the Compressed Gas Association. a The term atmospheric (atm) denotes the oxygen content normally present in atmospheric air; the numerical values denote the oxygen exposure, or acute adverse physiological symplimits for synthesized air. toms after prolonged exposure.” b The water content of compressed air required for any particular quality verification level may vary with the intended use from saturated to very dry. For breathing air used in conjunction with a self-contained breathing apparatus in extreme cold where moisture can This section discusses the production, puricondense and freeze, causing the breathing apparatus to malfunction, a dew point not to exceen -50°F (63 ppm v / v), or 10° lower fication, and distribution of a low-pressure than the coldest temperature expected in the area, is required. If a specific water limit is required, it should be specified as a limiting breathing air and individual breathing devices concentration in ppm (v / v) or dew point. Dew point is expressed in °F at 1 atmosphere pressure absolute, 101 kPa abs. (760 mm Hg). used to provide personnel protection only c Not required for synthesized air whose oxygen and nitrogen components are produced by air liquefaction. when used with supplied air systems. Low pres- d Includes water. sure for breathing air refers to compressed air e Not required for synthesized air when the nitrogen component was previously analyzed and meets National Formulary (NF) specification. pressures up to 250 psig (1725 kPa) delivered to f Not required for synthesized air when the oxygen component was produced by air liquefaction and meets United States Pharmacopeia

}

(USP) specification.

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CONTINUING EDUCATION: Life-Safety Systems lates and water vapor, whose allowable quantities have not been Constant-Flow System Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com established, must also be controlled because of the effects they Also known as a “continuous-flow system,” the constant-flow may have on different devices of the purification system, on the system provides a continuous flow of purified air through perpiping system, and on the end user of the equipment. sonnel respirators to minimize the leakage of contaminants into the respirator and to ventilate the respirator with cool or warm Contaminants Condensed Hydrocarbons Oil is a major contaminant in air depending on conditions. This system could be used in a wide variety of areas, ranging breathing air. It causes breathing discomfort, nausea, and, in from least harmful to most toxic, depending on the type of resextreme cases, pneumonia. It can also create an unpleasant pirator selected. taste and odor and interfere with an individual’s desire to work. In addition, the oxidation of oil in overheated compressors can produce carbon monoxide. A limit of 5 ppm has been established. Some types of reciprocating and rotary-screw compressors put oil into the airstream as a result of their operating characteristics. Accepted practice is to use only oil-free air compressors in order to eliminate the possibility of introducing oil into the airstream. Carbon Monoxide Carbon monoxide is the most toxic of the common contaminants. It enters the breathing-air system through the compressor intake or is produced by the oxidation of heated oil in the compressor. Carbon monoxide easily combines with the hemoglobin in red blood cells, replacing oxygen. The lack of oxygen causes dizziness, loss of motor control, and loss of consciousness. A limit of 10 ppm in the airstream has been established based on NIOSH standards. Carbon Dioxide Carbon dioxide is not considered one of the more dangerous contaminants. Although the lungs have a concentration of approximately 50,000 ppm, a limit of 1,000 ppm has been established for the breathing airstream. Water and Water Vapor Water vapor enters the piping system through the air compressor intake. Since no upper or lower limits have been established by code, the allowable concentration is governed by specific operating requirements of the most demanding device in the system, which is usually the CO converter, or the requirement of being 10°F lower than the lowest possible temperature the piping may experience. After compression, water vapor is detrimental to the media used to remove CO. The dew point of the airstream must be greatly lowered at this point in order to provide the highest efficiency possible for this device. Water vapor is removed to such a low level that breathing air with this level of humidity will prove uncomfortable to users. After purification, too much humidity will fog the faceplate of a full face mask. It will also cause freeze-up in the pipeline if the moisture content of the airstream in the pipe has a dew point that is higher than the ambient temperature of the area where the compressed-air line is installed. Solid Particles Solid particles known as “particulates” can enter the system through the intake. They are released from non-lubricated compressors as a result of friction from carbon and Teflon material used in place of lube oils. No limits on particulates have been established by code. Odor There is no standard for odor measurement. A generally accepted requirement is that there be no detectable odor in the breathing air delivered to the user. This requirement is subjective and will vary with individual users. Types of System There are three basic types of breathing-air system: constant flow, demand flow, and pressure demand. Plumbing Systems & Design

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Demand-Flow System The demand-flow system delivers purified air to personnel respirators only as the individual inhales. Upon exhalation, the flow of air is shut off until the next breath. Demand-flow systems automatically adjust to an individual’s breathing rate. This system requires tight-fitting respirators. Its application is generally limited to less harmful areas because the negative pressure in the respirator during inhalation may permit leakage of external contaminants. This system is designed for economy of air use during relatively short-duration tasks and is usually supplied from cylinders. Pressure-Demand System A pressure-demand system delivers purified air continuously through personnel respirators with increased air flow during inhalation. By continuously providing a flow of air above atmospheric pressure, leakage of external contaminants is minimized. This system also uses tight-fitting respirators, but the positive pressure aspect allows them to be used in more toxic applications. System Components The breathing-air system consists of a compressed-air source, purification devices and filters to remove unwanted contaminants from the source airstream, humidifiers to introduce water vapor into the breathing air, the piping distribution network, respirator outlet manifolds, respirator hose, and the individual respirators used by personnel. Alarms are needed to monitor the quantity of contaminants and other parameters of the system as a whole and to notify personnel if necessary. Compressed-Air Source The source of air for the breathing-air system is an air compressor and/or high-pressure air stored in cylinders. Cylinders use ambient air, which is purified to reduce or eliminate impurities to the required level, and compress it to the desired pressure. A typical schematic detail is shown in Figure 5. Air Compressor The standard for air compressors used to supply breathing air shall comply with the requirement for oilfree medical gas discussed in the “Compressed-Gas Systems” chapter. Medical-gas type compressors are used because these systems as a whole generate far fewer contaminants than other types of system. When a liquid-ring compressor is used, it has the advantage of keeping the temperature of the air leaving the unit low. It is also possible to use any type of compressor for this service, provided the purification system is capable of producing air meeting all the requirements of code. The air-compressor assembly consists of the intake assembly (including the inlet filter), the compressor and receiver, the aftercooler, and the interconnecting water-seal supply and the other ancillary piping. All of these components are discussed in the “Specialty Gases for Laboratories” section. PSDMAGAZINE.ORG

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Figure 5 System with Standby High-Pressure Breathing Air Reserve Simpo PDF Merge and Split Unregistered

Air compressors have a high first cost and are selected if the use of air for breathing is constant and continuous, making the use of cylinders either too costly or too maintenance intensive because of the frequent changing of cylinders. Storage Cylinder When high-pressure cylinders are used either as a source or as an emergency supply of breathing air, they shall be filled with air conforming to breathing-air standards. The regulator should be set to about 50 psi (340 kPa) depending on the pressure required to meet system demands and losses. The cylinders have a low initial cost and are not practical to use if there is continuous demand. Cylinders are best suited to intermittent use for short periods of time or as an emergency escape backup for a compressor. Aftercooler Some components of the purification system require a specific temperature in order to function properly. Depending on the type of compressor selected and the type of purification necessary, the temperature of the air leaving the compressor may have to be reduced. This is done with an aftercooler. Aftercoolers can be supplied with cooling water or use air as the cooling medium. Water, if recirculated, is the preferred method. The manufacturer of both the compressor and purification system should be consulted as to the criteria used and the recommended size of the unit. Purification Devices The contaminants that are problematic for breathing-air systems must be removed. This can be done with separate devices used to remove individual contaminants or with a prepiped assembly of all the necessary purification devices, commonly referred to as a “purification system,” which requires only an inlet and

outlet air connection. For breathing-air systems it is commonly done with a purification system. The individual purification methods used to remove specific contaminants are the same as those discussed in the “Compressed-Gas Systems” chapter. For breathing air, oil and particulates are removed by coalescing and other filters, water is removed by desiccant or refrigerated dryers, and carbon monoxide is removed by chemical conversion to carbon dioxide using a catalytic converter. Carbon Monoxide Converter The purpose of the converter is to oxidize carbon monoxide and convert it into carbon dioxide, which is tolerable in much greater quantities. This is typically accomplished by the use of a catalyst usually consisting of manganese dioxide, copper oxide, cobalt, and silver oxide in various combinations and placed inside a single cartridge. The material is not consumed but does become contaminated. The conversion rate greatly decreases if any oil or moisture is present in the airstream. Therefore, moisture must be removed before air enters the converter. Catalyst replacement is recommended generally once a year since it is not possible to completely control all contaminants that contribute to decreased conversion. Moisture Separator Water and water vapor are removed by two methods, desiccant and refrigerated dryers. The most common desiccant drying medium is activated alumina. For a discussion of air-drying methods, refer to the “Compressed-Gas Systems” systems. Odor Remover Activated, granular charcoal in cartridges is used for the removal of odors. Particulates Remover Particulates are removed by means of in-line filters. Generally accepted practice eliminates particulates 1 µ and larger from the piping system .

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CONTINUING EDUCATION: Life-Safety Systems 4. Level D protection is used where special respiratory or skin Humidifier Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com protection is not required but a rapid increase of contamiWhen water is removed from the compressed airstream prior nant level or degradation of ambient oxygen content is posto catalytic conversion, the dryer produces very dry air. If the sible. breathing-air system is intended to be used for long periods of time, very low humidity will dry the mucous membranes of If the hazard cannot be identified, it must be considered an the eyes and mouth. Therefore, moisture must be added to the immediate danger to life and health (IDLH). This is a condition airstream to maintain recommended levels. Humidifiers, often that exists when the oxygen content falls below 12.5% (95 ppm called “moisturizers,” are devices that inject the proper level of O2) or where the air pressure is less than 8.6 psi (450 mm/Hg), water vapor into an airstream. Some require a water connec- which is the equivalent of 14,000 ft (4270 m). tion. There are five general types of respirator available, as follows: A recommended level of moisture is 50% relative humidity Mouthpiece Respirators Used only with demand type in the compressed airstream. Care must be taken not to route systems, mouthpiece respirators are designed only to deliver the air-distribution piping through areas capable of having tem- breathable air. They offer no protection to the skin, eyes, or face. peratures low enough to cause condensation. If the routing is Their use is limited to areas where there is insufficient oxygen impossible to change, a worker will have shorter periods of time and no other contaminants could affect the eyes and skin. on the respirator. Half-Face-Piece Respirators Half-face-piece respirators cover the nose and mouth and are designed primarily for Combination Respirator Manifold and Pressure Reducer demand and pressure type systems. They are usually tightfitting This is a single component with multiple quick-disconnect outlets providing a convenient place both to reduce the pressure of and provide protection for extended periods of time in atmothe distribution network and to serve as a connection point for spheres that are not harmful to the eyes and skin. Often worn several hoses. A pressure gauge should be installed on the man- with goggles, these respirators are limited to areas of relatively ifold to ensure the outlet pressure is within the limits required low toxicity. Full-Face-Piece Respirators Full-face-piece respirators by the respirator. cover the entire face and are designed for use with constant-flow Respirator Hose and pressure-demand systems. They are tightfitting and suitable The respirator hose is flexible and is used to connect the resfor atmospheres of moderate and high toxicity. They are usually pirator worn by an individual to the central-distribution piping used in conjunction with full protective clothing for such tasks system. Code allows a maximum hose length of 300 ft (93 m) as chemical-tank cleaning where corrosive and toxic gas, mist, Personnel Respirators and liquids may be present. Since the face masks provide proThere are two general categories of respirator used for individual tection to the face and eyes, they are also suitable for other tasks, protection: air purifying and supplied air. such as welding and the inspection of tanks and vessels where The air-purifying type of respirator is portable and has self- there is an oxygen-deficient atmosphere. contained filters that purify the ambient air on a demand basis. Hood-and-Helmet Respirators Hood-and-helmet respiraThe advantages to its use are that it is less restrictive to move- tors cover the entire head and are normally used with a conments and is light in weight. Disadvantages are that it must not stant-flow system. They are loose fitting and suitable only for be used where gas or vapor contamination cannot be detected protection against contaminants such as dust, sand, powders, by odor or taste and in an oxygen-deficient atmosphere. This and grit. Constant flow is necessary to ventilate the headpiece type of respirator is outside the scope of this book, it is men- and to provide sufficient air pressure to prevent contaminants tioned only because of its availability. from entering the headpiece. The type of respirator selected depends on the expected Full-Pressure Suits Full-pressure suits range in design from breathing hazards. In the choice of a respirator, the highest loose-fitting, body-protective clothing to completely sealed, expected degree of hazard, applicable codes and standards, astronaut-like suits that provide total environmental life supmanufacturer recommendations, suitability for the intended port. They are designed to be used only with constant-flow systask and the comfort of the user are all important consider- tems and are suitable for the most toxic and dangerous environations. ments and atmospheres. The EPA Office of Emergency and Remedial Response has Component Selection and Sizing identified four levels of hazard at cleanup sites involving hazardous materials and lists guidelines for the selection of protec- Breathing-Air Source Air Compressor The air-compressor size is based on the hightive equipment for each: 1. Level A calls for maximum available protection, requiring a est flow rate, in cfm (L/min), required by the number and type of respirators intended to be used simultaneously and the minipositive-pressure, self-contained suit, generally with a selfcontained breathing apparatus worn inside the protective mum pressure required by the purification system. suit. The following general flow rates are provided as a prelimi2. Level B protection is required when the highest level of nary estimate for various types of respirator. Since there is a respiratory protection is needed but a lower level of skin wide variation in the pressure and flow rates required for variprotection is acceptable. ous types of respirator, the actual figures used to size the system 3. Level C protection uses a full face piece and air-purifying must be based on the manufacturer’s recommendations for the respiratory protection with chemical resistant, disposal specific respirators selected. garments. This is required when the contaminant is known 1. 4 scfm (113 L/min) for pressure-demand respirators. and the level is relatively constant. Typical of its uses is for 2. 6 scfm (170 L/min) for constant-flow respirators. asbestos removal. 10 Plumbing Systems & Design

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3. Up to 16 scfm (453 L/min) for flooded-hood respirators. The converter is sized based on the flow rate of the system. Simpo PDF Merge and Split Unregistered Version -Coalescing http://www.simpopdf.com Filter/Separator The coalescing filter/separa4. Up to 35 scfm (990 L/min) for flooded suits. tor is a single unit that removes large oil and water drops and 5. Add 15 scfm (425 L/min) of air for suit cooling if used. particulates from the airstream before the air enters the rest of High-Pressure Storage Cylinder High pressure cylinders the system. It is selected on the basis of maximum system presare used either to supply air for normal operation to a limited sure, flow rate, and the expected level of contaminants leaving number of personnel for short periods of time or as an emerthe air compressor, using manufacturer’s recommendations. If gency supply to provide a means of escape from a hazardous an oil-free compressor is used, a simple particulate filter could area if the air compressor fails. The main advantage to using be substituted for the coalescing filter. cylinders is the air in the cylinders is prepurified, and no further Dryers (Moisture Separators) purification of the air is necessary. The number of cylinders is based on the simultaneous use of Desiccant Dryers — The two types of desiccant media dryer most respirators, the cfm (L/min) of each and the duration, in min, commonly used are the single-bed dryer, which is a disposable the respirators are expected to be used, plus a 10% safety factor. cartridge, and the continuous-duty, two-bed dryer. When two-bed dryers are used, a portion of the air from the The total amount of compressed air in the cylinders should not be allowed to decrease too low. A low-pressure alarm should compressor is used for drying one bed while the other is in sersound when pressure falls to 500 psig (3450 kPa) in a cylinder vice. The compressor must be capable of producing enough air normally pressurized to 2400 psig (16 500 kPa) when filled to for both the system and dryer use. The single-bed dryer has a lower first cost but a higher operatcapacity. ing cost. The disposable cartridge often is combined with other Example 9-1 purification devices into a single, prepiped unit. An indicator is Establish the number of cylinders required for an emergency often added to the media so the need for replacement is indisupply of air for 8 people using constant-flow respirators require cated by a color change. 15 min to escape the area. Disposable units are best suited for short durations or occa1. 8 × 6 × 15 = 720 scfm + 72 (10%) = 792 scfm total required sional use, such as for replacement of a main unit during peri2. Next, find the actual capacity of a single cylinder at the ods of routine service. Because of their generally small size, only selected high pressure, generally 2400 psi (16 500 kPa), a limited number of respirators can be supplied from a single and divide the capacity of each cylinder into the total scfm unit. Other considerations are that these disposable units have required to find the number of cylinders required. a limited capacity, in total cfh, they can process. Manufacturers’ 3. If 1 cylinder has 225 scf, 792 ÷ 225 = 3.5. Use 4 cylinders. recommendations must be used in the selection of the size and number of replacement cartridges required for any application. Purification Components The two-bed unit, commonly called a “heatless dryer,” is simiThe air used to fill breathing-air cylinders is purified before being compressed. Breathing air produced by air compressors lar in principle to that discussed in the “Compressed-Gas Sysrequires purification to meet minimum code standards for tems” chapter. Such units are used for continuous duty. The two factors contributing to the breakdown of media are breathing air. Prior to the selection of the purification equipment, several fast-drying cycles and high air velocity. If a desiccant dryer is samples of the air where the compressor intake is to be located selected, the velocity of air through the unit shall conform to should be taken so specific contaminants and their amounts manufacturer’s recommendations. Velocity should be as low can be identified. The ideal situation is to have the tests taken at as is practical to avoid fluidizing the bed. High velocity requires different times of the year and different times of the day. These more cycles for drying, which means wasting more air. If the tests quantify the type and amount of contaminants present at size of the dryer is a concern, more drying cycles means smaller the intake. With this information known, the purification sys- dryer beds. Longer drying cycles reduce component wear. Refrigerated Dryers — Refrigerated dryers are used if there is tems needed to meet code criteria can be chosen. The other no requirement for a nitrous oxide converter and if the 35–39°F requirement is the highest flow rate that can be expected. With dew point produced is 10°F below the lowest ambient air temthese criteria, the appropriate size and types of purifier can be perature where any pipe will be installed. The refrigerated dryer selected. is less efficient than the desiccant dryer. Its advantages are that The most commonly used method of purification is an assemall the air produced by the compressor is available to the system bly of devices called a “purification system” specifically chosen and it has a lower pressure loss. and based on the previously selected criteria. Manufacturers’ When refrigerated dryers are preferred, several purification recommendations are commonly followed in the selection and devices are often combined into a single unit, including the sizing of the assembly. Carbon-Monoxide Converter The requirement for installa- refrigeration unit, filter/separator for oil and water, and a chartion of a carbon-monoxide converter is rare. The need for a con- coal filter for odor removal. This unit produces air that is lower verter is based on tests of the air at the proposed location of the in temperature than the inlet air. If the breathing-air distribution piping is to be routed through compressor intake. Another source of information is the EPA, which has conducted tests in many urban areas throughout the an area of lower temperature, the pressure dew point of the air country. Another indication that installation may be necessary must be reduced to 10°F lower than the lowest temperature is the use of a non-oil-free compressor. Good practice requires expected. Odor Remover Odors are not usually a problem, but their the installation of a converter if there is an outside chance the level of carbon monoxide may rise above the 10 ppm limit set removal is provided for as a safeguard. The activated charcoal cartridges remove odors are selected using manufacturers’ recby code. JULY/AUGUST 2006


CONTINUING EDUCATION: Life-Safety Systems Low-Air-Pressure Monitor The low-air-pressure monitor ommendations based on the maximum calculated flow rate of Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com the breathing-air system. The cartridges must be replaced peri- must sound an alarm when the pressure in the system reaches odically. a predetermined low point. This set point allows the users of the breathing-air system to leave the area immediately while Humidifiers Often called a “moisturizer,” a humidifier is required to increase still being able to breathe from the system. For cylinder storage, the relative humidity of the breathing air to approximately 50% this set point is about 500 psig in the cylinders. For a compresif required. The unit is selected using the increase in moisture sor system, the alarm should sound when the pressure falls to required for the airstream and the flow rate of air. Caution must a point 10 psig below the pressure set to start the compressor. be used so as not to increase the dew point of the compressed This should also switch over to the emergency backup supply air above a temperature 10°F lower than the lowest temperature if one is used. If no backup is used, the pressure set point shall be 5 psig higher than the minimum required by the respirators in any part of the facility the pipe is routed through. being used. Respirator Hose Dew-Point Monitor A dew-point monitor is used to meaThe respirator hose most often used to connect the respirator sure the dew point and sound an alarm if it falls to a low point, worn by an individual to the central-distribution piping system set by a health officer, that might prove harmful to the users. It is is 3⁄8 in. (10 mm) in size. Code allows a maximum hose length of required to alarm if the dew point reaches a point high enough 300 ft (93 m). The most common lengths are between 25 and 50 to freeze in some parts of the system. ft (7.75 and 15.5 m). High-Temperature Air Monitor Some purifiers or purifier components will not function properly if the inlet air temperaSystem Sizing Criteria ture is too high. The set point is commonly 120° F but will vary System Pressure The outlet pressure of the compressor shall among different manufacturers and components. be within the range required by the purification system. TypiFailure-to-Shift Monitor This monitor is placed on descally, the pressure is approximately 100 psi (70.3 kg/cm2). The iccant dryers to initiate an alarm if the unit fails to shift from precise range of pressure and flow rate shall be obtained from the saturated dryer bed to the dry bed when regeneration is the purification system manufacturer selected for the project. required. The pressure in the distribution system should be as high as possible to reduce the size of the distribution-piping network. Code requires the pressure be kept below 125 psi (88 kg/cm2). The distribution-piping pressure range is usually 90 to 110 psig (620 to 760 kPa) available in the system after the purifier. The pressure required at the respirator ranges from approximately 15 psig for pressure-demand respirators to 80 psig for full-flooded suits that require cooling. The actual requirements can be obtained only from the manufacturer of the proposed equipment because of the wide variations possible. Pressureregulating valves shall be installed to reduce the pressure to the range acceptable to the respirator used. Often, this reduction is done at the respirator manifold, if one is used, or, if a single respirator type with a single pressure is used throughout the facility, a single regulator can be installed to reduce the pressure centrally. Pipe Sizing and Materials The most commonly used pipe is type L copper tubing, with wrought copper fittings and brazed joints. For pipe sizing, follow the sizing procedure discussed in the “Compressed-Gas Systems” chapter. The number of simultaneous users must be obtained from the facility. No diversity factor should be used. Alarms and Monitors The following alarms and monitors are often provided: CO Monitor Usually included as a built-in component, this monitor measures the CO content of the airstream and sounds an alarm when the level reaches a predetermined high set point. Oxygen-Deficiency Monitor Used as a precautionary measure in an area where respirators are not normally required, the oxygen monitor measures the oxygen content of the air in a room or other enclosed area and sounds an alarm to alert personnel when the level falls below a predetermined level. Usually, several alarm points are annunciated prior to reaching a level low enough to require the use of respirators. 12 Plumbing Systems & Design

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Now Online! Starting with this issue, the technical article you must read to complete the exam will be located at www.psdmagazine.org. The following exam and application form also may be downloaded from the Web site. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

About This Issue’s Article The July/August 2006 continuing education article is “Life-Safety Systems,” Chapter 8 of Pharmaceutical Facilities Plumbing Systems by Michael Frankel. This chapter describes water-based emergency drench equipment and systems commonly used as a first-aid measure to mitigate the effects of such an accident. Also described are the breathing-air systems that supply air to personnel for escape and protection when they are exposed to either a toxic environment resulting from an accident or normal working conditions that make breathing the ambient air hazardous. You may locate this article at www.psdmagazine.org. Read it, take the following exam, and submit it to the ASPE office to potentially receive 0.1 CEU (comparable to 1.0 PDH).

CE Questions—“Life-Safety Systems” (PSD 134)

PSD 134


1. The recommended supply pipe size to an emergency shower is ________. a. ¾ inch, b. 1 inch, c. 1¼ inches, d. 1½ inches

8. The code-required flow rate from an emergency shower is ___________ gpm. a. 25, b. 30, c. 35, d. 40

2. Since oil is a major contaminant in breathing air systems, the maximum allowed is ___________. a. 5 ppm, b. 5 ppb, c. 10 ppm, d. 10 ppb

9. How many cylinders of air are required for an emergency supply of air for eight people using pressure demand respirators needing 15 minutes to escape the area? a. 2.3 use 3 cylinders b. 3.5 use 4 cylinders c. 4.7 use 5 cylinders d. cannot be determined

3. An emergency shower drench hose is used to _________. a. wash the floor after a chemical spill b. irrigate the body under the clothing prior to removal of the clothing c. provide a means to fill mop bucket d. none of the above 4. A failure-to-shift monitor is ___________. a. used to control multi-stage compressors b. used to initiate an alarm if a desiccant dryer fails to shift from the saturated bed to the dry bed when regeneration is required c. used to coordinate the output signal of the low air pressure monitor and the refrigerated dryer d. not required on modern systems 5. In areas where strong acid or caustic is used, the emergency shower and eyewash equipment should be located within ___________ feet of the potential source of the hazard per ANSI code Z-358.1. a. 5, b. 10, c. 15, d. 20 6. What is the established comfort zone water temperature for emergency drench equipment? a. 70–75°F, b. 75–80°F, c. 80–85°F, d. 85–90°F 7. As defined by “30 CFR 10,” a toxic environment has air that ___________. a. may produce physical discomfort immediately b. may cause chronic poisoning after repeated exposure c. may cause acute adverse physiological symptoms after prolonged exposure d. all of the above 14 Plumbing Systems & Design

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10. Refrigerated dryers are used ___________. a. when money is of no concern b. when order removal is not required c. when system pressure is high enough to accommodate them d. none of the above 11. The minimum diameter of the spray pattern from an emergency shower, measured at 60 inches above the surface on which the user stands, is ___________ inches. a. 18, b. 20, c. 22, d. 24

12. An oxygen content below 12.5 percent and/or a pressure of 8.6 psi should be considered ___________. a. as a Level A hazard as established by the EPA b. as a Level C hazard as established by the EPA c. as a Level E hazard as established by the EPA d. as an immediate danger to life and health

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Signature Expiration date: Continuing education credit will be given for this examination through July 31, 2007. Applications received after that date will not be processed.



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Life-Safety Systems (PSD 134)





Life-Safety Systems (PSD 134) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

JULY/AUGUST 2006



PSD 131

Medical Gas and Vacuum Systems



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Medical Gas and Vacuum Systems


General Health care is in a constant state of change, which forces the plumbing engineer to keep up with new technology to provide innovative approaches to the design of medical-gas systems. In designing medical-gas and vacuum systems, the goal is to provide a safe and sufficient flow at required pressures to the medical-gas outlet or inlet terminals served. System design and layout should allow convenient access by the medical staff to outlet/inlet terminals, valves, and equipment during patient care or emergencies. This section focuses on design parameters and current standards required for the design of nonflammable medical-gas and vacuum systems used in therapeutic and anesthetic care. The plumbing engineer must determine the needs of the health-care staff. Try to work closely with the medical staff to seek answers to the following fundamental design questions at the start of a project: 1. How many outlet/inlets are requested by staff? 2. How many outlet/inlets are required? 3. Based on current conditions, how often is the outlet/inlet used? 4. Based on current conditions, what is the average duration of use for each outlet/inlet? 5. What is the proper usage (diversity) factor to be used?

Medical-Gas System Design Checklist As any hospital facility must be specially designed to meet the applicable local code requirements and the health-care needs of the community it serves, the medical-gas and vacuum piping sys tems must also be designed to meet the specific requirements of each hospital. Following are the essential steps to a well-designed and functional medical-gas piped system, which are recommended to the plumbing engineer: 1. Analyze each specific area of the health-care facility to determine the following items: A. Which piped medical-gas systems are required? B. How many of each different type of medical-gas outlet/inlet terminal are required? C. Where should the outlet/inlet terminals be located for maximum efficiency and convenience? D. Which type and style of outlet/inlet terminal best meet the needs of the medical staff? 2. Anticipate any building expansion and plan in which direction the expansion will take place (vertically or horizontally). Determine how the medical-gas system should be sized and valved in order to accommodate the future expansion. 3. Determine locations for the various medical-gas supply sources.

A. Bulk oxygen (O2). B. High-pressure cylinder manifolds (O2, N2O or N2). C. Vacuum pumps (VAC). D. Medical-air compressors (MA). 4. Prepare the schematic piping layout locating the following: A. Zone valves. B. Isolation valves. C. Master alarms. D. Area alarms. 5. Calculate the anticipated peak demands for each medical-gas system. Appropriately size each particular section so as to avoid exceeding the maximum pressure drops allowed. 6. Size and select the various medical-gas and vacuum supply equipment that will handle the peak demands for each system, including future expansions. If this project is an addition to an existing facility, determine the following: A. What medical gases are currently provided and what are the locations and number of the stations? B. Can the current gas supplier (or the hospital’s purchasing department) furnish the consumption records? C. Are the capacities of the existing medical-gas supply systems adequate to handle the additional demand? D. Are any existing systems valved that could be used for an extension? Are the existing pipe sizes adequate to handle the anticipated additional loads? E. What type of equipment is in use and who is the manufacturer? Is this equipment state-of-the-art? F. Is it feasible to manifold the new and existing equipment? G. What is the physical condition of the existing equipment? H. Is there adequate space available for the new medical-gas supply systems and related equipment at the existing location? I. Is existing equipment scheduled to be replaced? (A maintenance history of the existing equipment may help in this determination.)

Number of Stations The first step is to locate and count the outlet/inlets, often called “stations,” for each respective medical-gas system. This is usually done by consulting a program prepared by the facility planner or architect. This program is a list of all the rooms and areas in the facility and the services that are required in each. If a program has not been prepared, the floor plans for the proposed facility shall be used. There is no code that specifically mandates the exact number of stations that must be provided in various areas or rooms for all health-care facilities. In fact, there is no clear consensus of opinion among medical authorities or design professionals as to how many stations are actually required in the facility areas. Guidelines are

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 2: “Medical Gas and Vacuum Systems.” ©2000, American Society of Plumbing Engineers. 44 Plumbing Systems & Design


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published by the American Institute of Architects Table 1 Outlet Rating Chart for Medical-Vacuum Piping Systems Merge and Split Unregistered Version - http://www.simpopdf.com (AIA), Simpo NationalPDF Fire Protection Association (NFPA), Zone Allowances— Corridors, Free-Air Allowance, cfm Risers, Main Supply Line, and ASPE that recommend the minimum number (L/min) at 1 atmosphere Valves of stations for various services in specific areas. Simultaneous Air to Be The most often-used recommendations in deter Location of Medical-Surgical Vacuum Usage Factor Transported,a Per Room Per Outlet (%) cfm (L/min) mining the number of stations for hospitals are those Outlets Operating rooms: necessary to be accredited by the Joint Commission Major “A” (Radical, open heart; organ for the Accreditation of Hospitals Organization transplant; radical thoracic) 3.5 (100) — 100 3.5 (100) 2.0 (60) — 100 2.0 (60) (JCAHO). Accreditation is required for Medicare and Major “B” (All other major ORs) 1.0 (30) — 100 1.0 (30) Medicaid compensation. The JCAHO publishes a Minor 1.0 (30) — 100 1.0 (30) manual that refers to the AIA guidelines for the mini- Delivery rooms Recovery room (post anesthesia) and mum number of stations for oxygen, medical air, intensive-care units (a minimum of 2 and vacuum that must be installed in order to obtain outlets per bed in each such department): — 3 (85) 50 1.5 (40) accreditation. If this is a factor for the facility, these 1st outlet at each bed 2nd outlet at each bed — 1.0 (30) 50 0.5 (15) requirements are mandatory. Other jurisdictions, 3rd outlet at each bed — 1.0 (30) 10 0.1 (3) such as state or local authorities, may require plans All others at each bed — 1.0 (30) 10 0.1 (3) to be approved by local health or building officials. Emergency rooms — 1.0 (30) 100 1.0 (30) These approvals may require adhering to the state Patient rooms: — 1.0 (30) 50 0.5 (15) or local requirements and/or NFPA 99, Health-Care Surgical Medical — 1.0 (30) 10 0.1 (3) Facilities. — 1.0 (30) 10 0.1 (3) If accreditation or the approval of authorities is Nurseries Treatment & examining rooms — 0.5 (15) 10 0.05 (1) not a factor, the number and area locations of sta- Autopsy — 2.0 (60) 20 0.04 (1) tions are not mandated. The actual count then will Inhalation therapy, central supply & — 1.0 (30) 10 0.1 (3) depend upon requirements determined by each instructional areas individual facility or another member of the design a Free air at 1 atmosphere. team using both past experience and anticipated Table 2 Color Coding for Piped Medical Gases future use, often using the guideline recommendaGas Intended for Medical Use United States Color Canada Color tions as a starting point. Oxygen Green Green on whitea Medical-Gas Flow Rates Carbon dioxide Gray Black on gray Each station must provide a minimum flow rate for the Nitrous oxide Blue Silver on blue proper functioning of connected equipment under Cyclopropane Orange Silver on orange design and emergency conditions. The flow rates and Helium Brown Silver on brown diversity factors vary for individual stations in each Nitrogen Black Silver on black system depending on the total number of outlets and Air Yellow* White and black on black and white the type of care provided. Vacuum White Silver on yellowa The flow rate from the total number of outlets, withGas mixtures (other than Color marking of mixtures shall be a combination of color out regard for any diversity, is called the “total conmixtures of oxygen and nitrogen) corresponding to each component gas. nected load.” If the total connected load were used for Gas mixtures of oxygen and sizing purposes, the result would be a vastly oversized nitrogen system, since not all of the stations in the facility will 19.5 to 23.5% oxygen Yellowa Black and white All other oxygen concentrations Black and green Pink be used at the same time. A diversity, or simultane-

Source: Compressed Gas Association, Inc. ous-use factor, is used to allow for the fact that not all a Historically, white has been used in the United States and yellow has been used in Canada to identify vacuum systems. of the stations will be used at once. It is used to reduce Therefore, it is recommended that white not be used in the United States and yellow not be used in Canada as a marking the system flow rate in conjunction with the total conto identify containers for use with any medical gas. Other countries may have differing specific requirements. nected load for sizing mains and branch piping to all parts of the distribution system. This factor varies for Medical-Gas System Dispensing Equipment different areas throughout any facility. Medical-gas outlet/inlet terminals Most manufacturers of The estimated flow rate and diversity factors for various systems, medical-gas system equipment offer various types of medicalarea stations, and pieces of equipment are found in Table 1. gas outlets. These medical-gas outlets are available in various gas Total demand for medical-gas systems varies as a function of orders (e.g., O2-N2O-Air), center-line spacing, and for exposed and time of day, month, patient-care requirements, and facility type. concealed mountings. Outlet types and configurations must meet The number of stations needed for patient care is subjective and the requirements of the local jurisdictional authority and NFPA cannot be qualified based on physical measurements. Knowing 99. All outlets must be properly identified and confirmed. Care the types of patient care and/or authority requirements will allow should also be taken to accurately coordinate the various pieces of placement of stations in usage groups. These groups can establish medical-gas dispensing equipment with the architect and medical demand and simultaneous-use factors (diversities), which are staff involved in the given project. If the project is a renovation, the used in the calculation for sizing a particular system. All medical- outlet types should match existing equipment. With prefabricated gas piping systems must be clearly identified using an approved patient headwall units, the medical-gas outlets are generally furcolor-coding system similar to that shown in Table 2. nished by the equipment manufacturer, and it is very important that coordination be maintained by the engineer so that unnecesJANUARY/FEBRUARY 2006


CONTINUING EDUCATION: Medical Gas and Vacuum Systems sary duplication of work is avoided. Also, with regard to the over- lets In critical-care areas, which are generally considered by Simpo PDF Merge and Splitthese Unregistered - http://www.simpopdf.com the-bed medical-gas service consoles, consoles areVersion often most individuals to be those locations of the hospital providing a specified in the electrical or equipment section of the specifica- special treatment or service for the patient (such as surgery, recovtion and medical-gas service outlets are specified, furnished, and ery, coronary, or intensive-care units), the designer’s selection and installed under the mechanical contract. placement of the medical-gas service equipment must be done Gas-outlet sequence, center-line spacing, and multiple-gang- very carefully in order to provide efficient work centers around the service outlets are some of the considerations to be taken into patient for the medical staff. account when requesting information from the various equipment Manufacturers of medical-gas service equipment usually promanufacturers. It is more practical, in terms of both the cost of the vide a wide range of equipment that is available for use in these equipment and the installation, to specify and select the manufac- areas. Depending upon the customer’s preference and the availturer’s standard outlet(s). Details and specifications regarding the able budget, the equipment is selected to provide the necessary individual standard outlets are usually available from all manufac- individual gas services and accessories. turers upon request. Table 3 provides a quick reference guide for the engineer to use The existing outlets are compatible with the adapters found on as a basis for selecting the commonly used types of outlet dispensthe hospital’s anesthesia machines, flow meters, vacuum regula- ing equipment. tors, etc. Care should be taken to make sure all future expansions Example 1 in the same facility have compatible equipment. The following illustrative example presents some of the most Patient head-wall systems A recent and growing trend in important critical-care area equipment and options for the selechospital construction is the requirement for patient head-wall tion of the equipment. systems, which incorporate many services for the patient’s care. Surgery medical-gas services to be piped include: These units may include the following: 1. Oxygen. 1. Medical-gas outlets. 2. Nitrous oxide. 2. Electrical-service outlets (including emergency power). 3. Nitrogen. 3. Direct and indirect lighting. 4. Medical compressed air. 4. Nurse-call system. 5. Vacuum. 5. Isolation transformers. 6. Waste anesthetic-gas disposal. 6. Grounding outlets. Providing medical-gas service outlets in the surgery room may 7. Patient-monitoring receptacles. be accomplished in several ways, such as the following: 1. Ceiling outlets Individual medical-gas outlets mounted in the 8. Vacuum slide and IV brackets. ceiling with hose assemblies providing the medical staff with 9. Night lights. connections from the outlets to the administering apparatus. 10. Electrical switches. This method is considered by most to be the most economiBed locator units are also available, which serve to provide cal means of providing an adequate gas service to the surgery power for the more advanced patient beds, telephone, night lights, and standard power. These units Table 3 Types of Dispensing Equipment for Specific Areas also function to protect the walls Medical Gas Outlet Dispensing Equipment from damage as beds are moved Ceilingand adjusted. WallPatient Mounted Rigid Retractable Ceiling Nitrogen Mounted Care Head Outlets with Ceiling Ceiling with Gas Control Head walls currently vary in Hospital Areas Outlets Wall Hose Stops Columns Columns Stacks Cabinets shape, size, type, and cost from a Autopsy rooms • • simple over-the-patient-bed stan Delivery rooms • • dard configuration to elaborate Emergency examination and treatment • • total-wall units. Most manufactur- rooms • • ers of medical-gas equipment offer Emergency operating rooms Induction rooms • medical-gas outlets for all types • • of patient consoles available in Labor rooms Major surgery rooms • • • • • • today’s market. When specifying Minor surgery, cystoscopy • • • head-walls outlets, the plumbing Neonatal intensive care units • • engineer should consider the folNormal nursery rooms • • lowing: Nursery workrooms • 1. Is the service outlet selected O.B. recovery rooms • • compatible with the existing Patient rooms • • outlet component? Pediatric and youth intensive care unit • • • 2. Does the patient head-wall Post-operative recovery rooms • • • manufacturer include the type Premature and pediatric nursery rooms • • • of medical-gas outlets required Pre-op holding rooms • • as part of the product? Radiology rooms • Special types of ceiling- Respiratory care unit • mounted, medical-gas out- Specialized surgeries (cardiac and neuro) • • 46 Plumbing Systems & Design


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areas. The ceiling gas-service outlets are generally located at Medical-Gas Storage Simpo PDF and Unregistered - http://www.simpopdf.com both the head and Merge the foot of the Split operating table in orderVersion to After deciding the medical-gas services to be provided at the facilprovide alternate positioning of the operating table. ity, the engineer should determine the storage capacity and the pipe sizing required and possible locations for the source. Local 2. Surgical ceiling columns Surgical ceiling columns are usucodes and references as well as the administrative authority having ally available in two designs: rigid (a predetermined length jurisdiction should be consulted for each medical-gas system. from the ceiling height above the floor) and retractable. Both Because of the unique characteristics of each medical-gas surgical ceiling columns provide medical-gas services within source, the gases are described separately in this section. Also, an enclosure that projects down from the ceiling. The ceiling an explanation of the techniques currently employed to exhaust columns are usually located at opposite ends of the operating anesthetic gases is provided. table in order to provide convenient access to the medical-gas Oxygen (O ) Several factors must be known when estimating outlets by the anesthesiologist. In addition to the medical-gas 2 the monthly consumption of oxygen in new or existing healthoutlets, these ceiling columns can be equipped with electricare facilities: cal outlets, grounding receptacles, physiological monitor 1. Type of medical care provided. receptacles, and hooks for hanging intravenous-solution bottles. 2. Number of oxygen outlets or Most manufacturers offering surgical ceiling columns allow for 3. Number of patient beds. many variations in room arrangements of medical-gas services 4. Future expansion of facility. and related accessories, depending upon the specific customer’s 5. In existing facilities, approximate consumption. needs and the engineer’s specifications. When specifying this Two methods can be used by the plumbing engineer to estitype of equipment, it is necessary to specify carefully all medicalmate the consumption of oxygen. The more accurate method is to gas service requirements and their desired arrangement(s). Also, obtain a detailed consumption record from the health-care facility the engineer must coordinate all other required services with the or obtain monthly oxygen shipment invoices from the supplier. If electrical engineer and medical staff. inventory records are not available from the health-care facility or 3. Surgical gas tracks Surgical gas tracks are forms of ceiling the supplier, use consumption records from a comparably sized outlet and hose-drop arrangements that allow the movement facility, with good judgment. of the hose drops from one end of the operating table to the The second method is to apply the following rule of thumb to other on sliding tracks mounted on the ceiling. These prodestimate the monthly supply of oxygen. This estimating method ucts are currently available from various manufacturers and should be used with good judgment. Always coordinate estimated all provide the same basic services. The proper selection and demand with the oxygen supplier during the design process. specification of specific types are based on individual cus1. In non-acute-care areas, allow 500 ft3 (14 m3) per bed per tomer preference. Many variations in products and particular month for supply and reserve oxygen storage. product applications are available in critical (intensive) care 2. In acute-care areas, allow 1000 ft3 (28 m3) per bed per month areas. Consultation with appropriate manufacturers for rec for supply and reserve oxygen storage. ommendations is always advisable. Oxygen supply sources are divided into two categories: (1) bulk4. Articulating ceiling-service center Articulated ceiling-seroxygen systems and (2) cylinder-manifold-supply systems. Bulkvice centers are moved by pneumatic drive systems and are oxygen systems should be considered for health-care facilities designed for the convenient dispensing of medical-gas and with an estimated monthly demand above 35,000 ft3 (991 m3) or electrical services in operating rooms. The medical-gas and equal to 70 oxygen outlets. Manifold systems are used in small electrical systems are complete for single-point connection to general hospitals or clinics. each outlet at the mounting support platform. Bulk-oxygen systems When selecting and placing bulk-oxygen High-pressure nitrogen (N2) dispensing equipment Special systems, there are several factors to be considered: Oxygen transconsideration must be given by the plumbing engineer to the port truck size, truck access to bulk-storage tanks, and NFPA 50, placement of the nitrogen outlets. The primary use of nitrogen gas Standard for Bulk Oxygen Systems at Consumer Sites. Bulk-oxygen in hospitals is for driving turbo-surgical instruments. Variations of equipment, construction, installation, and location must comply these turbo-surgical instruments, in both their manufacture and with NFPA 50 recommendations. If liquid oxygen is spilled or their intended use, will require that several different nitrogen-gas leaked, an extreme fire or explosive hazard could occur. NFPA has pressure levels be available. For this reason, it is necessary that design standards to minimize fire exposure to and from surroundthe engineer provide an adjustable pressure-regulating device ing structures. near the nitrogen gas outlet. A nitrogen control panel is usually Bulk-storage systems consist of cryogenic tanks that store liquid located on the wall (in the surgery room) opposite the operating oxygen at low pressures (225 psi [1551.3 kPa] or less). Cryogenic area sterile field. The installation should allow for the access and tanks are ASME unfired, double-walled, vacuum-insulated, presadjustment of pressure settings by a surgical nurse. sure vessels. Liquid oxygen has a boiling point (nbp) of –297.3°F Piping from the nitrogen control panel to a surgical ceiling outlet (–182.9°C) and a liquid density of 71.27 lb/ft3 (1141.8 kg/cm3). will provide a convenient source of nitrogen for surgical tools. This When vaporized into gas, it produces 900 times its liquid volume. will prevent hoses from being located on the floor or between the Furthermore, since the tank is changed less often, process stabil wall outlet and the operating table. Excess hose can be obstructive ity is maximized and the introduction of atmospheric impurities to the surgical team. is reduced. Tank systems are furnished with an integral pressurerelief valve vented to the atmosphere should the liquid oxygen convert to a gas. JANUARY/FEBRUARY 2006


CONTINUING EDUCATION: Medical Gas and Vacuum Systems Figure 1 Typical Bulk Supply System (Schematic)


Most bulk-oxygen storage systems are furnished with vaporizers. Vaporizers are banks of finned-tube heat exchangers that convert the liquid to its gaseous state. The vaporizers come in several styles—including atmospheric, powered (forced-air, steam, and electric), waste-heat, and hybrid—and sizes. The selection of vaporizers should be based on demand, intermittent or continuous usage, energy costs, and temperature zones. Poorly ventilated sites or undersized heat exchangers can cause ice to form on vaporizers during the conversion process. Excessive ice formations can clog and damage the vaporizer. Also, ice could allow extremely cold gas or the cryogenic liquid to enter the piped system; damage the valves, alarms, and medical components; and even injure patients. Figure 1 illustrates a typical bulk-oxygen system schematic. Automatic controls furnished with the tanks regulate the flow of liquid through the vaporizers. When there is a demand for oxygen, the supply system draws liquid from the bottom of the cryogenic storage tank through the vaporizers. The gas moves through a final line regulator. Thus, a constant supply of oxygen at a regulated pressure is provided. In case of mechanical difficulty or the depletion of the liquidoxygen supply, the reserve supply will begin to feed into the distribution system automatically. An alarm signal should alert appropriate hospital personnel when the liquid in the oxygen storage tank reaches a predetermined level. The alarm signals should indicate low liquid levels, reserve in use, and reserve low. Cylinder-manifold supply systems Compressed-oxygen systems are comprised of cylinder manifolds that allow a primary supply source of oxygen cylinders to be in use and an equal number of oxygen cylinders to be connected as a reserve supply. 48 Plumbing Systems & Design JANUARY/FEBRUARY 2006

The controls of the cylinder manifold will automatically shift the flow of the oxygen gas from the service side to the reserve side when the service side is depleted. Manifold systems can be located indoors or outdoors. When manifolds are located indoors, the engineer should observe the following: • Location Preferably, the manifold should be in a dedicated room on an outside wall near a loading dock and have adequate ventilation and service convenience. • Adjacent areas There should be no doors, vents, or other direct communications between the anesthetizing location or the storage location and any combustible agents. If locating near or adjacent to an elevated temperature area is unavoidable, the engineer should specify sufficient insulation to pre vent cylinder overheating; • Fire rating The fire-resistance rating of the room should be at least 1 h. • Ventilation Outside ventilation is required. • Security The room (or area) must be provided with a door or a gate that can be locked and labeled. Oxygen manifolds are sized taking into consideration the following: 1. The size of the cylinders, 244 ft3 (6909 L) H-cylinder (see Table 4 for a sizing chart). 2. The hospital’s usage of oxygen, in ft3 (L) per month.

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reconstituted from oxygen U.S.P. and nitrogen N.F. must comply,

Table 4 Selection Chart for Oxygen Manifolds Simpo PDF Merge and Split Unregistered Versionas- ahttp://www.simpopdf.com minimum, with Grade D in ANSI ZE86.I, Commodity SpecifiHospital Usage Duplex Manifold Size 3 Cu. Ft. (10 L) per month Total Cylinders Cylinders per Side 5,856 (165.8) 6 3 9,760 (276.4) 10 5 13,664 (386.9) 14 7 17,568 (497.5) 18 9 21,472 (608.0) 22 11 25,376 (718.6) 26 13 29,280 (829.1) 30 15 33,154 (938.8) 34 17

Note: Based on use of 244 ft3 (6909.35 L) H-cylinders.

Nitrous oxide (N2O) The common source of nitrous oxide is a cylinder-manifold system. High-pressure manifold systems consist of two banks of cylinders, primary and reserve. (See discussion under “Oxygen,” above.) System demands for nitrous oxide can be more difficult to determine than they are for other medical gases. The number of surgeries scheduled, the types and lengths of surgery, and the administering techniques used by the anesthesiologists cause extreme variations in the amount of nitrous oxide used. Because of this variation, considerations must be given to the size and selection of the nitrous-oxide manifold system. Avoid locating the nitrous-oxide manifold system outdoors in areas with extremely cold climates. Nitrous oxide is supplied liquefied at its vapor pressure of 745 psi (5136.6 kPa) at 70°F (21.1°C). At extremely cold temperatures, the cylinder pressure will drop dramatically, reducing the cylinder pressure to a point where it is impossible to maintain an adequate line pressure. This is due to a lack of heat for vaporization. For nitrous-oxide manifolds located indoors, the same precautions previously listed for oxygen systems must be observed. The following should be considered when selecting and sizing nitrous-oxide manifolds and determining the number of cylinders required: 1. The size of the cylinders: 489 ft3 (13 847 L) K-cylinders (see Table 5). 2. The number of anesthetizing locations or operating rooms. 3. Provide ½ of 1 cylinder per operating room for in-service and reserve supplies. Table 5 Sizing Chart for Nitrous Oxide Cylinder Manifolds Duplex Manifold Size Indoor Outdoor Number of Operating Cylinders per Cylinders per Rooms Total Cylinders Side Total Cylinders Side 4 4 2 4 2 8 8 4 10 5 10 10 5 12 5 12 12 6 14 7 16 16 8 20 10

cation for Air. Medical compressed air can be produced on site from atmospheric air using air compressors designed for medical applications. There are three major types of air compressor in the marketplace today: the centrifugal, reciprocating, and rotary screw. The reciprocating and rotary screw are “positive-displacement” type units, while the centrifugal compressor is a “dynamic” type compressor. The medical air compressor shall be designed to prevent the introduction of contaminants or liquid into the pipeline by one of two methods: Type 1 air compressors eliminate oil anywhere in the compressor. Type 2 air compressors separate the oil-containing section from the compression chamber. Examples of a type 1 compressor are the liquid ring, rotary screw, and permanently sealed bearing compressor. Type 2 compressors have extended heads. A positive-displacement compressor is normally rated in actual cubic feet per minute (acfm). This is the amount of air taken from atmospheric conditions that the unit will deliver at its discharge. Within a broad range, changes in inlet air temperature, pressure, and humidity do not change the acfm rating of either the reciprocating or the rotary screw compressor. The centrifugal compressor’s capacity, however, is affected slightly by the inlet air conditions due to the nature of the compression process. For example, as the air temperature decreases, the capacity of the dynamic compressor will increase. The capacity of a centrifugal compressor is normally defined in inlet cubic feet per minute (icfm) . In an effort to obtain an “apples to apples” comparison of various compressors, many manufacturers specify their capacity requirements in standard cubic feet per minute (scfm). This sometimes causes much confusion because many people do not fully understand how to convert from acfm or icfm to scfm. The design engineer specifying scfm must define a typical inlet air condition at the building site and their set of “standard” conditions (normally 14.7 psia [101.4 kPa], 60°F [15.6°C], and 0% relative humidity). Typically, the warmest normal condition is specified because as the temperature goes up scfm will go down. To convert from acfm to scfm, the following equation is used. Equation 1 scfm = acfm ×

Pi – (Ppi × %RH) × Tstd Pstd – (Pp std × %RHstd) Ti

where Pi = Initial pressure Ppi = Partial initial pressure of water vapor in 100% humid air at the temperature in question RH = Relative humidity Pstd = Pressure under standard conditions Pp std = Partial standard pressure of water vapor in 100% humid air at the temperature in question RHstd= Relative humidity at standard conditions Tstd = Temperature at standard conditions, °F (°C) Ti = Inlet temperature, °F (°C)

Note: Based on use of 489 ft3 (13.85 × 103 L) K-cylinders.

Medical compressed air Medical compressed air may be supplied by two types of system: (1) a high-pressure cylindermanifold system; and (2) a medical air-compressor system. The manifold systems for compressed air are similar in configuration to those for oxygen and nitrous oxide (see discussion under “Oxygen,” above). Air supplied from cylinders or that has been JANUARY/FEBRUARY 2006


CONTINUING EDUCATION: Medical Gas and Vacuum Systems Equation 1a dryers, in-line filters, regulators, dew-point monitors, and valves. Merge Split Unregistered VersionThe - http://www.simpopdf.com This Simpo equationPDF is derived fromand the Perfect Gas law, which is: compressor components are connected by piping that allows equipment isolation, provides pressure relief, and removes conP V P1V1 = 2 2 densate from receivers. Medical-air compressors must draw out T1 T2 side air from above the roof level, remote from any doors, windows, or: P T 1 2 and exhaust or vent openings. Where the outside atmospheric air is V2 = V1 × P × T 2 1 polluted, special filters can be attached to the compressor’s intake where to remove carbon monoxide and other contaminants. Refer to P1 = Initial pressure NFPA 99 for proper location of medical-air intakes. Medical com V1 = Initial volume pressed air must comply with NFPA 99 and/or Canadian Standards T1 = Initial temperature P2 = Final pressure Association’s (CSA’s) definition of air-quality standards. V2 = Final volume Where more than two units are provided for the facility, any two T2 = Final temperature units must be capable of supplying the peak calculated demands. For a reciprocating or rotary-screw compressor, the conversion Provide automatic alternators (duty-cycling controls) to ensure from acfm to scfm is simple. The inlet air conditions and standard even wear in normal usage. Alternator controls incorporate a posiconditions are inserted into the above formula and multiplied tive means of automatically activating the additional unit (or units) by the acfm capacity of the unit. It makes no difference what the should the in-service pump fail to maintain the minimum required design conditions are for that compressor, as these do not figure pressure. Medical compressed air produced by compressors may be into the formula. In the case of a dynamic compressor, the icfm air defined as “outside atmosphere to which no contaminants (in the flow at the given inlet conditions is inserted in place of the acfm form of particulate matter, odors, oil vapors, or other gases) have in the formula. Another design issue that the engineer should be been added by the compressor system.” Not every compressor is aware of is how altitude affects the output of the compressor. At suitable for use as a source for medical compressed air in healthaltitudes above sea level, all medical-air systems have reduced care facilities. Only those compressor units specifically designed flow. In these cases, the required sizing will need to be adjusted and manufactured for medical purposes should be considered as to compensate. To do this, multiply the scfm requirements by the a reliable source of oil-free, moisture-free, and low-temperature correction factor in Table 6. compressed air. Acceptable compressor types include oil-free, oilTable 6 Altitude Correction Factors for Medical-Air Systems less, and liquid-ring compressors. Separation of the oil-containCorrection ing section from the compression chamber by at least two seals is Normal Barometric Factor for SCFM required by the compressor manufacturers. Altitude, ft (m) Pressure, in. Hg (mm Hg) (L/min) Air compressed for medical-breathing purposes are to be used Sea level 29.92 (759.97) 1.0 (28.31) for this purpose only and should not be used for other applica 1,000 (304.8) 28.86 (733.04) 1.01 (28.6) tions or cross-connected with other compressed air systems. 2,000 (609.6) 27.82 (706.63) 1.03 (29.16) Table 7 Minimum Pipe Sizes for Medical Air-Compressor Intake Risers 3,000 (914.4) 26.82 (681.23) 1.05 (29.73) Pipe size, in. Flow rate, cfm 4,000 (1219.2) 25.84 (656.33) 1.06 (30.01) (mm) (L/min) 5,000 (1524) 24.90 (632.46) 1.08 (30.58) 2.5 (63.5) 50 (1416) 6,000 (1828.8) 23.98 (609.09) 1.10 (31.14) 3 (76.2) 70 (1985) 7,000 (2133.6) 23.09 (586.48) 1.12 (31.71) 4 (101.6) 210 (5950) 8,000 (2438.4) 22.23 (564.64) 1.15 (32.56) 5 (127.0) 400 (11330) 9,000 (2743.2) 21.39 (543.3) 1.17 (33.13) 10,000 (3048) 20.58 (522.7) 1.19 (33.69) Table 7 provides the minimum pipe sizes for medical air-comIn other words, to correctly size the medical-air system, you would apply the correction factor listed in the chart above to the peak-calculated load (scfm) at sea level.

pressor intake risers. Consult with the compressor manufacturer on intake recommendations and allowable friction loss for the intake riser before finalizing the pipe size equipment selection. ✺

Example 2 A facility is located at 5000 ft (1524 m) above sea level and the system demand is 29.4 SCFM. Take the 29.4 scfm and multiply it by 1.08 (correction factor from Table 5) to get the adjusted scfm requirement of 31.8 scfm at 5000 ft above sea level. Therefore, a medical-air system of greater capacity is needed at higher altitudes. Another handy formula for compressed-air systems is the following: to convert scfm to L/min multiply by 28.31685. Each compressor must be capable of maintaining 100% of the medical-air peak demand regardless of the standby compressor’s operating status. The basic compressor package consists of filter intakes, duplex compressors, after-coolers, receiving tanks, air



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Continuing Education from Plumbing Systems & Design Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Kenneth G.Wentink, PE, CPD

Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PS&D), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status. ASPE features a technical article in every issue of PS&D, excerpted from its own publications. Each article is followed by a multiple-choice test and a simple reporting form. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of 90% or higher on the test,

you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years. No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PS&D within the past 12 months. However, CEU credit only can be obtained on a total of eight PS&D articles in a 12-month period. Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

CE Questions—“Medical Gas and Vacuum Systems” (PSD 131) 1. When liquid oxygen is vaporized into a gas, it produces ________ times its liquid volume. a. 0 b. 450 c. 900 d. 1,350

7. In acute-care areas, allow ________ cubic feet per bed per month for supply and reserve oxygen storage. a. 250 b. 500 c. 750 d. 1,000

2. Nitrous oxide (N2O) is typically used by whom in the surgery room? a. the attending physician b. the attending physician’s assistant c. the surgical nurse d. the anesthesiologist

8. The exact number of medical-gas outlets required in the various areas or rooms is mandated by ________. a. the various codes that apply to work at the project site b. the American Institute of Architects (AIA) c. the National Fire Protection Association (NFPA) d. none of the above

3. The medical-gas and vacuum piping systems must be designed to ________. a. meet the specific requirements of each hospital b. anticipate any building expansion c. not cross connect to any existing system d. all of the above 4. The primary use of nitrogen gas in hospitals is ______ __. a. driving turbo-surgical instruments b. pressurizing piping systems c. in the laboratory Bunsen burners d. none of the above 5. Medical-gas flow rates ________. a. must include diversification b. must provide for the total connected load c. must provide the minimum required flow for the proper functioning of connected equipment d. must be estimated 6. Providing medical-gas service outlets in the surgery room may be accomplished by locating them in ______. a. the ceiling b. the surgical ceiling columns c. the surgical gas tracks d. any of the above noted areas and others not listed



9. Medical-gas outlet types and configurations must meet the requirements of the local jurisdictional authority and ________. a. ANSI 1416 b. NFPA 99 c. NFPA 50 d. ANSI 1763 10. Several factors must be known when estimating the monthly consumption of oxygen, such as ________. a. the number of patient beds b. the type of medical care provided c. the future expansion plans of the facility d. all of the above 11. What is the SCFM correction factor for a medical-air system located in a facility at an altitude of 7,000 feet above sea level? a. 1.05 b. 1.08 c. 1.12 d. 1.17 12. The goal in designing medical-gas and vacuum systems is ________. a. to provide a safe system b. to provide a sufficient flow of gas or vacuum c. to provide the required pressure d. all of the above

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Medical Gas and Vacuum Systems (PSD 131) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________



Reflecting Pools and Fountains

PSD 133



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CONTINUING EDUCATION Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com

Reflecting Pools and Fountains Introduction Reflecting pools and fountains provide visual and auditory pleasure, add charm to garden areas, and provide a retreat area in which to rest and relax. Fountains generate sound and provide a cooling effect on hot summer days. Fountains may be selfcontained units or pre-engineered kits or they may be custom designed and built. Self-contained fountains, consisting of pools, pumps, valves, lights, and other hardware, are shipped assembled, and the addition of water is all that is necessary to put the fountain into normal operation. No permanent connections to the plumbing system are required. Pre-engineered fountain kits, complete with equipment, need only assembly and hook-up to the water-supply, drainage, and power sources. Plumbing engineers, architects, and landscape architects are all involved in the creation of display fountains and reflecting pools. The architects are concerned with the overall aesthetics, whereas the engineers must be familiar with the available fountain equipment and the technical details of each component if they are to design systems that will achieve the desired display effects. The plumbing engineer should work closely with the architect and the landscape architect to achieve the desired display. In addition, the systems should be designed with provisions for cleaning, water treatment, and maintenance. Custom fountains providing small or large water displays with almost any desired decorative effects are discussed in this chapter. Also included are the technical details of pool design; mechanical equipment, including spray systems; and operation and maintenance. The engineer must also be aware that the fountain is usually represented on a set of architectural drawings as an undefined space or a rendering. It is also usually the last item to be coordinated. What this means is that the engineer usually designs the fountain in its entirety, including the water effect and its influence on the surrounding area. Then, he/she needs to quickly (and accurately) select the nozzles, determine flow rates, select the equipment, try to get space for the equipment, coordinate with the other disciplines involved, then coach contractors, who look upon a fountain as a glorified swimming pool. When all this is done, however, the engineer can look upon a beautiful piece of engineered art that will most likely never be duplicated and can be proud to claim it as his/ her work.

Pool Design General Considerations A number of general items of information should be kept in mind when designing a fountain. For an engineer or designer, the most important issue surrounding any body of water is safety. There is always a risk attached to a water feature. It is not the intent of this chapter to acquaint the engineer with drowning and entrapment issues, but the engineer is encouraged to study the available codes

and standards regarding swimming pools and spas and apply them as necessary. Many jurisdictions regard 18 in. (457.2 mm) of water as the maximum depth allowed without severe access restrictions, such as railings, fences, and gates. From a mechanical, operating perspective, the most important thing is to locate all pumps to ensure flooded suction lines. If at all possible, locate the pumps so that the operating water level of the fountain is above the suction inlet of the pump. This helps to prevent cavitation and to ensure that the pump primes quickly. Painting the pool interior a dark color helps to conceal piping, lighting, cable, junction boxes, and other equipment located in the pool, and, in addition, provides reflective qualities. But the dark color tends to cause an increase in water temperature by absorbing the sun’s heat. This, in turn, creates a requirement for more chlorine. Thin or fine-mist spray effects are difficult to see against light colors, mixed colors, or lace-type backgrounds. A massive display should be used under these conditions. The construction of pools at or below grade level creates a potential problem with leaves and other debris blowing into the pool, therefore, this should be avoided. Reflecting pools and fountains may be installed above or below grade. Above-grade fountains offer the advantage of adding more height to the water display. Multilevel pools provide the possibility of having numerous waterfall displays with only one water source. Aerating nozzles that use a venturi action to entrain air into the water stream can cause a wave action in circular pools. In such cases, surge collars or underwater baffles should be installed to minimize this action. Water will splash horizontally approximately one half the height of the water display except where wind is a problem. Since wind can push water long distances, it is important to locate nozzles so that the splash and wind effect will not create undue problems. It may be advisable to provide a wind control to lower the height of the display or to shut off the system when there is too much wind. Water hitting water creates a lot of noise. There are times and locations when this is desirable. When the noise is too loud, however, it can be reduced by locating various types of planting around a pool. Multilevel Pools Multilevel and multiple pools involve special considerations, which, if taken into account, do not present any difficulty. If these considerations are not taken into account, however, disaster can result. The amount of flow over a waterfall is determined by the height of the water flowing over the weir. This height over the weir is the same as the height of the pool behind the weir. When the pumps stop, this water will all come over the weir and spill into the pool below. The water in the air (i.e., the waterfall) will also come to rest in the lower pool. The lower pool must be sized

Reprinted from American Society of Plumbing Engineers Data Book Volume 3: Special Plumbing Systems, Chapter 5: “Reflecting Pools and Fountains.” © 2000, American Society of Plumbing Engineers. 62 Plumbing Systems & Design

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to accommodate this extra water. For the water in the air, the actually measure the depth over a weir. If the client desires an Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com depth over the weir times the height of the water is sufficiently unbroken sheet of water over the weir into the pool, a rule of accurate to calculate the volume. thumb is about ¼ in. (6.35 mm) of water over the weir per 4 ft of Multilevel pools should have some method of draining the vertical drop. upper pools. A small drain line with a screw plug at the upper The four most common types of weir are the rounded edge; pool can be used. The drain line should be a maximum of 1¼ in. the upward-tapered weir; the downward-tapered weir; and the (31.75 mm) to restrict the discharge rate into the lowest pool. downward-tapered, metal-edge weir. The rounded-edge weir For multiple pools with different elevations, a common refer- is used when it is desired to have the water run down the wall ence must be established to drain the basins. An example would surface. The upward-tapered weir requires more water than the be waterfalls at several different elevations with basins at sev- other types and should not be used for waterfalls exceeding 5 ft in eral different elevations served by a single pump system. If the height. The downward-tapered weir is very effective in creating pumps were turned off, the water in the basins would all drain smooth sheets for waterfalls up to 15 ft in height. The downward- to the lowest basin through the common suction header. To pre- tapered, metal-edge weir achieves the same effect as the downvent this, either check valves must be installed in all suction and ward-tapered weir with the added advantage of being easier to discharge lines or all basins must drain to a surge pit. The surge level. pit provides a common reference for the pumps and allows The waterfall or weir is normally supplied from a trough each basin to drain independently of the others. The surge pit behind the weir edge. The trough can be supplied with water method is also much easier to balance than the method with by many methods as long as the surface disturbance is kept to check valves. (See Figure 1.) a minimum. A header can be installed with holes drilled along the length of the header to supply water equally along the length of Figure 1 Multilevel Pools with a Surge Pit the trough. Hydrophilic well piping, precut with slots along the length of the pipe, makes a very smooth supply method. Oversized inlets (to lower the water velocity) in the bottom of the trough with diverter plates can also be used. Weir lips must be level. This is difficult to achieve with poured concrete, therefore, a metal or plastic lip should be provided. If the spill lip is in the shape of an overhang, a drip lip in the shape of a ¼ in. (6.35 mm) deep rectangular slot should be provided under the slot. This will prevent the water from running down the wall. Filtration turnover The filtration turnover rate is determined by the For multiple pools at the same elevation, an equalizer line volume of the pool and the desired number of hours per comshould be run between the pools. No matter how accurate the plete water change. The filtration turnover can vary from 4 to calculations and installation, two identical pools will have vary- 12 h per complete water change. This needs to be determined ing flow rates. The equalizer line should not tie into any other by the engineer. For areas with blowing dust and debris, a line except a valved drain. The equalizer should be sized so that faster water change is needed. For cleaner areas, such as those it is as large as the largest line coming into the pools. If each pool indoors, a slower water change can be used. The filtration flow receives the discharge through a 4-in. (100-mm) line, the equal- rate is determined by dividing the pool water volume, in gallons izer should be a 4-in. (100-mm) line. (liters), by the turnover time, in minutes. Example 1 Preliminary Display Selection and Determination of An 8000-gal pool divided by (12 h x 60 min) equals 11.1 gpm Flow Rates flow rate. Spray jets and nozzles The flow rates for spray jets and nozzles (A 30 283-L pool divided by [12 h x 60 min] equals 45.42 L/min should be determined by the manufacturer’s data. Most manuflow rate.) facturers publish catalogs showing the various types of jet in operation. The client should be given the opportunity to select Therefore, a filtration system sized for a flow rate of 12 gpm the jets from a subjective standpoint; the selection should then (45.42 L/min) would be adequate. be reviewed by the engineer for practicality. Weirs Weirs are normally sized by the length of the weir and the depth of the water flowing over the weir edge. The engineer may have to assist the client in determining the effect desired. It is useful to have the client see an existing water feature then

Inlet/Outlet and Device Location By convention, an “inlet” is defined as a device allowing water to flow into the pool. An “outlet” is defined as a device allowing water to leave the pool. MAY/JUNE 2006


CONTINUING EDUCATION: Reflecting Pools and Fountains Main drains Main drains are provided for pump suction and Mechanical space or vault The pumping equipment can be Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com draining the pool. Main drains should be located at the lowest located in the building, in an underground equipment vault, or point of the pool. There should be at least one main drain for outdoors above ground in a protected area. The determination the lowest basin. Main drains should be located so that there is as to whether or not to provide a vault depends on the following not more than 20 ft between drains or more than 15 ft from the factors: (1) the distance from the pool to the mechanical space sidewall of the pool. The main drains should be sized to accom- in the building vs. the distance from the pool to an underground modate the full flow of the system. Main-drain gratings should vault; (2) the difference in cost for piping, electrical wiring, and be sized at no greater than 1.5 fps through the grating. See the conduit between the two locations; (3) the cost of the mechanimanufacturer’s listings for the approved flow rate through anti- cal space vs. the cost of a vault; and (4) whether or not mechanivortex gratings. cal space is available. Main drains used for pump suction must have some method If the equipment is installed in an area remote from the founof preventing entrapment: either they must be the anti-vortex tain, it is advisable to have a remote-control panel located within type or they must be view of the fountain. installed in pairs at Figure 2 Main Drains Provide adequate space for all fountain equipment, including least 4 ft apart to preelectrical panels. Observe all code-mandated clearance requirevent suction entrapments. Allow some method of removing motors and pumps that ment. Although reflectwill not require the removal of parts of the building. This could ing pools and fountains be an overhead crane rail or merely an eye bolt attached to the are not intended to be structure over each motor for lifting. occupied by humans, A floor drain is required near the equipment. Specify a floor people do accidendrain with a backwater valve if there is any possibility of water tally (and on purpose) backing up through the drain, especially in a vault. If a floor fall into them. Pairdrain cannot flow by gravity to the sewer, a sump pit and pump ing drains and using is required. If the equipment is installed in a vault, a batteryanti-vortex drains operated, backup sump pump may be desirable. minimizes the risk of In a vault, provide an electric receptacle; a light; a hose bibb; suction entrapment and disembowelment. If paired drains are a ventilating blower; intake and exhaust vents; an access ladder; used, they must be connected to a common suction line without and a lockable, spring-loaded access hatch big enough for all any intervening valves. (See Figure 2.) equipment to pass through. A heavy manhole cover is not Main drains are used to empty the pool for cleaning and to recommended because the maintenance personnel become drain storm water when the pool is empty. A drain line is run to annoyed with lifting the cover and tend to forget their maintethe nearest storm drain line and a valve is installed in this line. nance duties. In some cases, a 3-ft deep vault with an access Skimmers Skimmers are necessary in all pools to collect hatch covering the entire vault is adequate. windblown debris and dust. Even indoor pools can collect an Fountain Systems and Components amazing amount of floating debris that must be cleaned out The fountain system consists of the following major systems: periodically. Skimmers normally consist of a skimmer body that 1. Display system. is cast into the pool wall, a floating weir, and a strainer basket. The floating weir draws a thin layer of water into the skimmer. 2. Piping system. With a thin layer, the water’s velocity is higher and its influence 3. Water-treatment system. extends farther out into the pool. Skimmer strainer baskets need A. Mechanical-filtration system. to be cleaned out periodically, and access to the strainer defines B. Chemical-treatment system. the type of skimmer used. Top-access skimmers, while easiest to 4. Makeup-water system. maintain, are very visible. Since architects prefer to hide every 5. Overflow and drainage system. component possible, front-loading skimmers are preferred. In 6. Lighting system. addition, front-loading skimmers are less prone to vandalism. Skimmers should be located so that there is 1 skimmer pro- 7. Other miscellaneous systems. The reflecting pool may or may not have a display system, vided for each 500 ft2 (46.45 m2) of lower basin, with a minimum of 1 skimmer. The skimmer system should be sized to accom- depending on the desired effect. Each of these systems often overlaps or relies on another modate the full filtration flow. A 2-in. (50.8-mm) skimmer can accept about 30 gpm (113.56 L/min), but skimmers can be system to function correctly. For instance, if the filtration system ganged together to increase their capacity. A majority of the is not working properly, the spray heads will load up with debris skimmers should be located such that the prevailing winds and and not function correctly. If the water is not kept at the proper level with an autofill, the lighting system may overheat. current blow the debris toward them. Filtration return inlets Filtration return inlets come from the Display System filters and return clean water to the pool. Return inlets should be There are two distinct display types: static and dynamic. Static placed at least 12 in. (304.8 mm) below water level to minimize displays have a constant or nearly constant volumetric flow rate surface disturbance. If the pool is too shallow, increase the inlet at all times. Examples include a waterfall weir and constantpipe size to reduce the velocity into the pool. Each pool should height jets. Dynamic displays vary the flow through the system. have a minimum of 2 inlets, with a sizing criteria of 1 inlet per Examples are dancing fountains, where the fountain appears to 600 ft2 (0.093 m2) of basin. Inlets should be sited to direct flow react to music or lights, and waterfalls and rivers that are part toward the skimmers. 64 Plumbing Systems & Design

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of a simulated storm scenario. For either type of display, the System and Component Selection and Design Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com typical system consists of the following components: suction Criteria outlets and suction piping, pump(s), return piping, and disFilter Systems charge device(s). The display system for each type of effect, e.g., Types of filter There are many types of filter on the market nozzles, weirs, whirlpools, and waves, should have a different today. Some of these are specialty filters for water treatment, pump system dedicated to it. RO systems and the like. For fountains, swimming pool and spa Piping System filters best fit the application. Mechanical filtration is required Two separate types of piping systems are defined for any foun- to remove suspended particulates down to about 50 µ. In this tain. These are the display systems and the filter system. The range, cartridge filters and high-rate, pressure sand filters are piping for these systems can normally share suction outlets but the best choice for fountains. should remain separate from there until returning to the pool. An There is a division in filter sizes that occurs around the 120 example of a poor design is a fountain system where the display gpm (454.25 L/min) flow rate. Above that rate are the commerwater and the filter water are combined such that a single pump cial filters used on larger pools and fountains and below are the draws from the pool and pumps through the filter then back to residential filters used on smaller pools and fountains. Many the nozzle. When the filter is clean, this system will work fine. As manufacturers do not make a distinction regarding quality at soon as the filter gets dirty, however, the flow from the nozzle will the different levels, but some do. Check with the distributors gradually drop until the filter is backwashed. Then the cycle will and pool contractors as to which filters cause the least trouble. begin again. When sizing filters, it is good practice to use more than one filter when the flow rate is above 120 gpm (454.25 L/min). For examWater-Treatment System ple, a system that requires 280 gpm (1059.92 L/min) of filtration The water-treatment system consists of two separate processes. would do better with two filters sized at 140 gpm (529.96 L/min) First, mechanical filtration removes the solids and some of the each than one filter sized at 280 gpm (1059.92 L/min). The reason suspended organics from the water. Second, the chemical filtrais cleaning time. Whether the filter selected is a cartridge, sand, tion disinfects and balances the water to provide clean, sparor diatomaceous earth (DE), it will have to be cleaned at some kling clear, odor-free water that is pleasing to the eye and not time. With multiple filters, the filtration process continues while detrimental to the pool and equipment. one filter is being cleaned. In the case of sand filters, the filter type Makeup-Water System of choice for most large systems, the backwash flow rate is lower, It is essential to maintain the proper water level in the pool. necessitating a smaller backwash pit and sewer line. The reasons are threefold. First, certain spray nozzles require With multiple filters, use multiple pumps. Although the pumps that the water level vary no more than ½ in. (12.7 mm) in are not to be piped individually to each filter, a pump can be order to achieve the desired display. A variation in the water shut down while a filter is serviced. This will prevent overrunlevel causes the nozzle display to become erratic and to differ ning the other filters while one filter is down. from the original design. Second, underwater lights must be Cartridge filters Cartridge filters are lower in first cost than submerged to a specific depth to both protect the lights and to the other types of filters and are relatively easy to maintain. The remove heat. Third, a substantial water-level drop could cause filter consists of a body constructed of plastic or stainless steel the suction line to entrain air, resulting in pump cavitation and that contains a polyester element. The cartridge filter element is possible damage. cleaned by removing the filter top and pulling out the element. It can then be hosed clean and reinstalled in the body. These filOverflow and Drainage System The fountain must be equipped with an overflow system ters are available in sizes ranging from 150 gpm down to 5 gpm. to handle storm water and the possible malfunction of the The small-size filters are of the inline type made for filtering spas makeup-water system. In addition, mundane reasons, such as and are excellent for small fountains. Cartridge filters must be removed from the body to be cleaned draining the pool for winter and cleaning, mandate that a drain and require some space to be hosed down. This is a considersystem be installed. ation when the fountain is indoors and requires that the carWater-Heating System tridges be taken away to be cleaned. A second set of cartridges If a fountain is to be kept in operation during the winter months will be necessary for a swap. and it is possible for the water to freeze, an aquastat-controlled Cartridges should be sized at 0.375 gpm/ft2 maximum flow pool heater should be provided. The heater should be sized to rate. maintain pool water at about 35 to 40°F (1.67 to 4.44°C). High-rate, pressure sand filters A pressure sand filter consists of a body constructed of plastic, fiberglass, or stainless steel Lighting System Underwater lights are used to provide illumination for the vari- that contains sand to filter the water. The term “high rate” comes ous displays. The number of lights depends on the overall size from the flow rate per square foot of sand bed. If the flow rate of the pool, the depth of the water, the height and width of the is above about 10 gpm (37.85 L/min), the filter is classified as water display, and possible interference from ambient lighting. “high rate.” There are sand filters that are considered “low” or “slow” rate, but they are seldom specified today. Water enters Lights can be white or another color as desired. the filter at the top and is pumped down through the sand to an underdrain manifold with slots narrow enough so that the water will pass but the sand will not. The water is piped to the sand filter through a series of valves (see Figure 3) or a multiport valve. A multiport valve is a single-handle control with four ports MAY/JUNE 2006


CONTINUING EDUCATION: Reflecting Pools and Fountains Figure 3 Fountain Components Simpo PDF Merge

tions allow effluent to flow to the

and Split Unregistered Version - http://www.simpopdf.com storm sewer, others require it to go to the sanitary sewer. Provision must be made to handle the large flow rates that are customary with a sand-filter backwash. Although the backwash only lasts 5 min at maximum, an enormous amount of water can be used in that time. Backwash rates are generally 20 gpm/ft2 of filter area. A high-rate, pressure sand filter is generally sized at 12 to 15 gpm/ ft2 of filter area, although the filter may be rated up to 20 gpm/ft2. Sizing filters To size a filter, first determine the filtration rate through the pool. Once this is established, divide the filtration rate by 0.375 for cartridge filters or 12 to 15 for sand filters. This will determine the required filter area. For filtration rates over 120 gpm (454.25 L/min), dual filters should be considered, with the flow divided equally between them. Filters should never be sized at their maximum allowed flow rate. This will cause higher pressure drops through the filter over the filter run and will substantially increase the energy used by the pump.

that can be configured to either filter, backwash, rinse, shutoff, bypass, or drain. They are limited to filters with 3-in. (80-mm) or smaller connections. Either the valve series or the multiport valve may be automated. As the filter accumulates debris, the differential pressure across the filter will increase. When the differential pressure has increased to a specific point, normally about 15 psi, the filter has reached the limit of its effective filter run and requires cleaning. Cleaning is accomplished by backwashing. Backwashing a sand filter is exactly what it sounds like. Backwashing reverses the flow so that the pump now forces water through the underdrain manifold with enough flow to lift the sand bed and stir it around. The debris is floated out of the sand and flows out the inlet pipe to a drain. A backwash sight glass should be installed to allow the operator to see when the effluent is clear. Provisions must be made with the project plumbing engineer if a sand filter is to be used. Many jurisdictions require that a sand filter be backwashed into a sand trap to prevent sand from entering the sewer system. Some jurisdictions require that a sand filter backwash as an indirect waste into a pit. The ultimate destination of the backwash effluent must also be determined. Some jurisdic66 Plumbing Systems & Design

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Pumps Display pumps Display pumps can be the dry type, the self-priming dry type, or the submersible type. When it is necessary to locate the pump above water level, a self-priming pump should be used. If the size and cost of a self-priming pump preclude its use, a foot valve or check valve may be installed in the suction line. Submersible pumps are more expensive than dry-type pumps and may require additional water depth in the pool. This can be accomplished by providing a pump pit in the water and installing a fiberglass grating over the pit. The grate offers protection from vandals and also hides the pumps from view. The advantage of using a submersible pump is that it can eliminate the need for long runs of pump suction and discharge piping, thereby saving on horsepower. Since there is less piping and corresponding friction loss, the required pump head is lower. In some cases, this can mean a substantial difference in horsepower. The National Electric Code does not allow submersible pumps over 230 V to be installed in fountains. Dry-type pumps are installed in a vault adjacent to the pool or a mechanical equipment room within the building. The preferred installation is one where the pump-suction inlet is located below the pool’s operating water level. If this is not allowed, a self-priming pump may be used. In most projects, an end-suction, close-coupled, centrifugal pump is used, but there are PSDMAGAZINE.ORG

some projects where a horizontal, split-case, centrifugal pump filter. There can be a substantial difference between these two Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com is necessary. This can occur where the flow rate is high and the conditions in pump flow, and a variable flow-control device required pump head is low. In all cases, the pump selection might be considered for evening out the flow rates. should be made using the manufacturer’s pump curves. Mul- Pump strainers and suction screens As a general rule, suction tiple pumps in parallel are preferred to one large pump. Redun- strainers protect the pumps and discharge strainers protect the dancy, wind control, and opportunities for different displays nozzles. Display pumps are not as likely to pick up waterborne are excellent reasons for multiple pumps. Some fountains have debris as are filter pumps, which are connected to skimmers displays that require high-pressure, low-flow nozzles; low-pres- and main drains. Provisions can be made for display pumps to sure, high-flow nozzles; and waterfall discharges. Where there have gratings over their suction outlets in the fountain. are multiple types of display, a separate pumping system should Basket strainers on the pump suction protect the pump be used for each type. from waterborne debris, which could get caught in the impelDisplay pumps are sized according to the hydraulic calcu- ler. Although display pumps can be protected somewhat from lations for friction loss and flow rate. Pumps can be cast iron, debris large enough to damage the pump, filter pumps should bronze or plastic. Pump materials should be suitable for contact always have basket strainers. with fresh water. Since vaults and mechanical spaces are freY-type strainers are mostly used to protect nozzles with small quently tight, it should be possible to remove the pumps’ motors openings. They are installed on the discharge side of display and impellers without disconnecting the piping. Pumps should pumps to intercept waterborne debris before it jams inside an be equipped with suction basket strainers with removable bas- actuator or orifice. The strainer should be equipped with a valve kets, suction and discharge gauge taps, isolation and balancing and hose connection to allow for easy blowdown. valves, eccentric and concentric reducers as required, and flexSuction diffusers are installed on the suction inlet to the pump ible connectors. Proper pump piping practices, as described and allow for rapid changes in the direction of piping close to elsewhere in the Data Book, should be followed. the pump. The diffuser slows the water down and straightens To size the display pump the following steps should be fol- it so that it enters the pump with less turbulence. Suction diflowed: fusers are also equipped with screens but they are very difficult to remove for cleaning and should probably not be used when 1. Determine the static head required between the lowest other methods are available. water level and the highest water level. This is important for multilevel fountains. Piping and Valves 2. Determine the head required at the discharge point. ManuMost piping for fountains is made of Schedule 40 PVC plastic. facturers provide charts that give the gpm and pressure Easy handling, light weight, and low friction losses make it the required at the nozzle. If the discharge is for a waterfall piping of choice in most fountains. Although PVC seems to be effect with the discharge point submerged, use 10 ft of head. the perfect choice, there are some caveats pertaining to its use. Piping installed through pool walls and floors and into the pool 3. Calculate the friction loss in the piping, fittings, and valves. should be copper or brass. PVC piping exposed to sunlight will 4. Add the results to obtain the required pump head. become brittle, unless it is specifically made to withstand the 5. Determine the total gpm as required for the nozzles, using effects of ultraviolet rays. Pump suction and discharge piping the manufacturer’s charts (or the gpm for a weir, as calcuinstalled underground or within a building can be PVC where lated using the weir length and depth). allowed by the local authorities. Be aware that smooth holes 6. Select the pump using the manufacturer’s pump curves. have been found in plastic piping installed underground. The If the exact flow rate and head cannot be obtained, select University of Illinois and the University of Florida both deterthe next larger size pump. In almost all cases, the pump mined that the holes were caused by termites. They do not eat selected should have a flat pump curve. Select the motor the PVC; they chew through it when it gets in the way of their that will provide a nonoverloading condition for the entire continued foraging for food. Also, be aware that most codes do length of the pump curve. Wide-open conditions are not allow plastic piping to be installed in a plenum. Ductile iron, common in water effects. galvanized steel pipe, or stainless-steel pipe can be used if large Filter pumps Filter pumps may be of the same type as the dis- pipe sizes are required and PVC cannot be used. Carbon-steel play pumps. (See discussion above.) There are few reasons why piping should never be used in a fountain due to the highly oxygenated water running through the piping. all the pumps cannot be of the same type. All buried piping should be treated as a water-service applicaFilter pumps are sized to match the gpm (L/min) required for a proper filtration rate and the head required to give that rate with tion. Specifically, piping needs to be bedded in sand or clean, a dirty filter. Components in the filter system that contribute to rock-free backfill. All changes of direction in piping 3 in. (76.2 head loss include: skimmers and main drains (piped in paral- mm) and larger need to be restrained with poured concrete thrust lel so that the longest run must be determined), valves, basket blocks. Starts and stops in fountain systems can cause severe strainers, face piping (the piping connecting the pump to the water hammer and resultant failure in unrestrained systems. All piping penetrations into the pool wall should be water filter), return piping, and return inlets. Elevation changes need to be accounted for and added or subtracted. Generally, since stopped in some fashion. A common method is to use a “puddle return inlets are below the water level, there is no net elevation flange” attached to the pipe itself. For penetrating walls into mechanical rooms, a mechanical pipe seal can be used. (See change. It is important that the pump be sized to give the proper flow Figure 4.) Unions or flanges should be used at the final connection to rate with a dirty filter, but it is also important that the engineer calculate the operating point on the pump curve with a clean all equipment so that the equipment can be easily removed for MAY/JUNE 2006


CONTINUING EDUCATION: Reflecting Pools and Fountains pump, should be properly braced within the mechanical room.

Figure 4 WallMerge Penetrations Simpo PDF and Split Unregistered VersionFire-protection - http://www.simpopdf.com bracing methods may be used. Return piping to multiple inlets (nozzles, etc.) must be hydraulically balanced. Filter return piping terminates in either adjustable or nonadjustable return fittings. Return fittings can be wall or floor mounted and should be adjusted to direct flow to the main drain and skimmers. Dead spots should not be allowed in a pool. Hydraulic balancing Suction and return headers should be hydraulically balanced as closely as possible to ensure even flow throughout the fountain. (See Figure 5.) For applications where the fountain can be encircled by a header, this provides an excellent balancing tool. Nozzle patterns and return inlet headers can be sized using the following equation: Equation 1 qn = 2.45C(D2)(2ghn)

repairs. Drainage lines from the overflow and drain lines should be either PVC or cast iron, as required by local code. Water makeup and fill lines should be copper tubing. Different metal pipes carrying water or installed underground must not come into contact with each other (dielectric isolation). All piping systems should be pressure tested immediately after installation, and the test should be left on until the piping is ready to be connected to the inlet and outlet devices and equipment. This way, a glance at a pressure gauge can indicate immediately if a pipe has been broken during another phase of the construction. The test pressure should be limited to 50 psi (344.74 kPa), since the fountain piping systems are operated at relatively low pressures. If the system requires higher pressure, the pressure test should be made at a pressure that is 25 psi (172.37 kPa) higher than the operating pressure. Make sure that plastic piping is tested within the pressures recommended by the manufacturer. Prior to connecting the devices and equipment, piping systems should be flushed and cleaned. Caps should be left on until ready to make the final connection to prevent debris from entering the piping. More than one pump has been damaged or had reduced flow due to debris that was in the pipe before the pump was connected. Suction-line piping Size the suction line at a velocity not to exceed 6 fps for copper piping and 10 fps (3.05 m/s) for plastic piping. Provide a suction inlet designed so that the drain will not trap a person in the pool. This is accomplished by having dual drains spaced at least 4 ft apart or dual drains located in different planes (such as a bottom drain and a sidewall drain) or by using anti-vortex drains. Some means of preventing vortexing should be used to prevent cavitation of the pumps. If a minimum of 18 in. (457.2 mm) of water cannot be provided over a suction drain, size the drain for ½ of the manufacturer’s recommended maximum flow and add more drains as necessary. Suction-line piping should be installed without vertical loops, which can become air bound. In addition, it is critical that suction piping pass a 25 psi (172.37 kPa) pressure test because a void as small as a pinhole can prevent a self-priming pump from pumping. Return piping Return piping should be sized at 6 fps maximum for copper piping and 10 fps maximum for plastic piping. Return piping, especially piping close to the discharge of the 68 Plumbing Systems & Design

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where qn = Discharge from orifice n, gpm (L/min) 2.45 = Conversion factor used to express the discharge in gal/ min (L/min) when the diameter is expressed in inches (mm) and the velocity is expressed in fps (m/s). Figure 5 Hydraulic Balancing

PSDMAGAZINE.ORG

C = Orifice discharge coefficient (usually = 0.61 for holes throttling. Since adjusting the fountain is very subjective, almost Simpo PDF Merge and Split Unregistered Versionevery - http://www.simpopdf.com drilled in the field) valve in the system could be involved in the final adjust D = Diameter of orifice, in. (mm) ments. This limits the selection to ball-and-globe valves for the g = Acceleration due to gravity, 32.2 ft/s2 (9.81 m/s2) smaller pipe and butterfly valves for the larger pipe. Lug-type, hn = Head on orifice n, ft. (m) butterfly valves are normally used in applications where equipment needs to be disconnected while still under water pressure. The head on orifice n is equal to: A pump room that is much lower than the fountain will be best Equation 2 served by lug valves at the equipment connections so that the 1 2 equipment can be serviced without draining the fountain. hn = (2.45CD q 2 2 n ) 2g Check valves There are several types of check valve, but 2 = kqn most are of two types: gravity and spring loaded. The gravity, or = k(mq1)2 swing-check, valve must be installed in a prescribed manner. The gravity check should be installed where water pressure will 2 = m h1 help provide a positive closure. Where a check valve must be where installed on a horizontal line, a spring check should be installed. k = Constant A foot valve is a special type of check valve that is installed in h1 = Head on orifice 1, ft (m) the pump-suction line. The purpose of a foot valve is to prevent m = Mass flow rate the suction line from draining back into the pool and causing The head loss between orifice 1 and n, which corresponds to the the pump to lose prime. A valved line from the makeup system should be installed between the pump and the foot valve to aid head loss in the distribution pipe between orifice 1 and n, is: in priming. It would be prudent also to install a drain in that secEquation 3 tion of pipe. ∆h(1–n) = h1 – hn Pressure-regulating valves Dynamic fountains are designed Now it can be shown that the head loss between the first orifice using pressure-regulating valves. The regulating valve maintains and the last orifice in a distribution pipe with multiple, evenly a selected downstream pressure regardless of the changes in spaced orifices is approximately equal to one-third of the head the upstream pressure. Therefore, when the spray height of one loss that would occur if the total flow were to pass through the set of nozzles is raised or lowered, the regulating valve keeps a same length of distribution piping without orifices. Thus, second set of nozzles at the same spray height. Actuator-control valves In addition, actuator-controlled, Equation 4 motorized, or pneumatic valves can be controlled using a 4 to hfdp = 1⁄3 hfp 20-milliamp (mA) electrical signal. The valve can be set to be = ∆h(1–n) fully closed at 4 mA and fully open at 20 mA. At any point in where between, the valve will be open an amount corresponding to the hfdp = Actual head loss through distribution pipe, ft (m) position of the point within this range. For example, at 6 mA, the hfp = Head loss through pipe without orifices, ft (m) valve will be slightly open and at 15 mA it will be almost fully The head loss through the pipe can be computed using the open. A computer can be programmed to provide signals to Hazen-Williams equation: open and close the valves in any pattern desired. Materials A sample schedule of piping materials is shown in Equation 5 Table 1. hfp = 10.5 (L1–n) Q 1.85D – 4.87 C Discharge Devices where Many return methods are used to return the water into the pool. hfp = Head loss through the pipe from orifice 1 to orifice n, ft The designer must choose which method either creates the least (m) disturbance to the desired water effect or creates the desired L1–n = Length of pipe between orifice 1 and n, ft (m) water effect. Q = Pipe discharge, gpm (L/min) Weir pools Common methods of return into upper weir pools C = Hazen-Williams coefficient (150 for plastic pipe) are: diverter plates (often anti-vortex drains used on the return D = Inside diameter of pipe, in. (mm) side), well screens, and double tees. (See Figure 6.) The difference in discharge between orifice 1 and n for a given Spray jets Numerous types of nozzle are manufactured. The distribution pipe and orifice size can now be determined using designer should select the type of that will provide the desired Equations 5-1 through 5-5. If the computed value of m is too low (<0.98), Table 1 Sample Schedule of Materials Indoor/ Abv/Blw Size, in. the size of the distribution pipe can System Outdoor Grade (mm) Pipe Material Fittings Joints be increased. The percent difference Static display piping Either Either ½–24 Sch. 40 PVC Socket Solvent weld in flow between 1 and n will be [(1 (12.5–600) – n) × 100]. A good value would be less Dynamic display piping Either Either ½–16 Sch. 80 PVC Socket Solvent weld (12.5–400) than 2%. Filtration piping Either Either ½–24 Sch. 40 PVC Socket Solvent weld Valves (12.5–600) Shutoff valves Most valves for Makeup water Either Either ½ –4 Type L copper Wrot copper Solder (12.5–100) fountains are of a type that allows Makeup water Either Either 6+ (150+) Type 302 Type 302 Mechanical stainless steel stainless steel groove

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CONTINUING EDUCATION: Reflecting Pools and Fountains for most manufacturer’s jets with a zone of 1-2 in. wherein the

Figure 6 Discharge Devices and Split Unregistered Version - http://www.simpopdf.com Simpo PDF Merge jet will function. These jets are slightly less expensive than the

independent type but require that the level be maintained very accurately. Using jets in a pool that empties over a weir is a very good application of this jet. Using jets to surround a geyser that erupts every few seconds is not a good application, as the water will surge a great deal. In the latter case, a water-level independent jet would be the answer.

spray effect. This can only be done by referring to the data listed in the manufacturer’s catalogs. Nozzles are available to provide solid or aerated columns of water, pyramid-like columns of water, aerated mounds of water, mushroom shapes, floating dandelion effects, fan-shaped sprays, finger-like fan sprays, belllike shapes, twirling jets, and numerous other effects. All aerating jets of various types fall into two categories: waterlevel dependent and water-level independent. The water-level dependent type of jet relies on the water level in the pool being constant. This constant level allows the jet to aspirate air into the water to give a pleasing, frothing effect. There is a range of depths 70 Plumbing Systems & Design

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Controls Remote control Display pumps and filter pumps should be controlled from a point within view of the fountain. This can be achieved with a remote, hard-wired control panel and key switches or a radio signal. Radio remote-control units that control several separate electrical loads by means of a hand-held transmitter and a manual switching panel are available. These enable a doorman or concierge to quickly shut down the fountain in the event of a problem, such as someone jumping into the fountain. Pump starters All pumps should have starters with overload protection to protect their motors. A disconnect switch must be installed within view of the pump. The engineer should verify that these items are provided for under the scope of electrical work. Wind controls Wind controls reduce the height of a fountain display or shut off the display pump. A time-delay relay keeps the pump off for at least 3 min to avoid the problem of pump cycling. Three methods are used to reduce the height of the fountain display: 1. The wind control opens or closes a solenoid or motorized valve, thereby bypassing water from the nozzles back into the pool and reducing the spray height of the nozzles. The valve and bypass line must not be undersized, or the required flow will not be bypassed. 2. A pressure-regulating valve can be installed in the discharge line of the display pump, and a reduced-pressure setting is used to lower the spray height. This method is somewhat more expensive than the bypass-control valve. 3. If the display pumps consist of two or more pumps in parallel, shutting down a pump will reduce the height by slightly less than the proportional amount produced by the shut down pump. Reduced friction in the discharge line will slightly increase the discharge of the remaining pump. With all these methods, hydraulic calculations are required to determine that the capacities and friction losses are adequate to achieve the desired effect. A two-stage wind control is often used, in which the first stage reduces the height of the display and the second stage turns the system off completely. Time switches Various types of time switches are available, from electric motor operator to electronic. Time switches can be used to operate the pumps at the desired times. In addition, cycle timers can be used to turn solenoid valves on and off at preset intervals of 5 s or more. Pressure and flow switches Pressure and flow switches are used to shut pumps off in the event that the pressure or flow drops too low in the pump discharge. They are also used to signal water-treatment systems of flow/no flow conditions. Start/stop switches are equipped with time-delay relays to allow the pump to be started and also to keep the pump off for a programmable delay to prevent pump cycling. PSDMAGAZINE.ORG

Total Btu/h heat loss = [203 × surface area of the pool in ft2 Lighting Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com (m2)] + [34 × sidewall area in ft2 (m2)] Lights are available in low-voltage as well as normal line voltage. Some jurisdictions, such as the City of New York, require only • 20 mph wind velocity low-voltage lighting and approval of all lights and transformers Total Btu/h heat loss = [176 × surface area of the pool in ft2 used in the jurisdiction. Most lights can be obtained with col(m2)] + [33 × sidewall area in ft2 (m2)] ored lenses if desired. Rock guards are required. Maintain the water level over the lights as required by the manufacturer. The • 15 mph wind velocity 2 National Electrical Code (NEC) must be followed when install- Total Btu/h heat loss = [145 × surface area of the pool in ft 2 2 2 (m )] + [32 × sidewall area in ft (m )] ing underwater lights, transformers, and submersible pumps. All electrical systems that supply power to equipment or lights It is also necessary to include the heat loss from the piping. in the pool must have ground-fault interrupter circuit breakers. Select a heater with an output equal to the Btu/h heat loss. In Fountain lights should be installed directly under the water many large buildings, the heating medium can be the heating hot display to illuminate the general pool area as well as the water water or steam. The heater is controlled by a temperature condisplay. The number of lights and the wattage depend on the trol with the sensing bulb located in the inlet pipe to the heater. overall size of the pool, the height and width of the water dis- The control will turn on the heater if the incoming water from the play, and possible interference from ambient lighting. pool is below 35°F (1.67°C) and shut it off if the temperature is Free-standing lights are wired through a bronze, underwater above 37°F (2.78°C). A flow switch in the inlet to the heater will junction box. The box must be listed by a nationally recognized prevent operation of the heater if there is insufficient or no flow. testing agency and approved for underwater use. The cable from The heater should be located on a bypass line, as shown in Figure the light is fed through a compression seal that is connected 7. The piping within 3 ft of the heater should be Type L copper to the junction box. When the architect wants to conceal the tubing. cable, the cable is fed through a compression seal to an adjacent Water-Treatment System brass conduit to a remote junction box. The cable must be long A properly engineered water-treatment system will allow the enough to reach the remote junction box without splices. operator to maintain a sparkling clear, odor- and algae-free pool. Niche lights that are installed in pool walls have conduit Certain water-treatment methods should be engineered into directly connected to the niche and extended to a remotely the system and certain water-treatment methods can be adminlocated switch box. The cable must be long enough to reach the istered by the operator. Water-treatment parameters include: remote junction box without splices. 1. Disinfectant residual—measured in parts per million (ppm). Lights are usually controlled by either astronomical time switches or regular time switches and a photocell. It is advisable 2. Oxidation reduction potential (ORP)—a measure of the cleanliness of the water. Measured in millivolts (mV). to design the control system so that maintenance personnel are not required to adjust the light timers for daylight savings time 3. pH—a measure of the acidity or causticity of the water. and changing sunset times. In general, selecting colors for the lights should be done with care Figure 7 Piping Schematics because of the subjective nature with which each person views the fountain. If blue, red, amber, and other dark colors are used, the lights should have a higher wattage. Water Heating Equipment If a fountain is to be kept in operation during the winter months and it is possible for the water to freeze, a pool water heater should be provided. The pool heater can be a steam heat exchanger, a hot-water heat exchanger, an electric water heater, or a gas-fired water heater. The heater should be sized to maintain the pool water at a minimum of 35°F (1.67°C). Overall heat loss due to surface evaporation, radiation, conduction, and convection for concrete pools where the water temperature is 35°F (1.67°C) and the air temperature is 10°F (–12.2°C) can be obtained as follows: • 25 mph wind velocity MAY/JUNE 2006


CONTINUING EDUCATION: Reflecting Pools and Fountains 4. Alkalinity—a measure of the resistance of the water to tion point should be downstream of the filter. Solid or dry chloSimpo PDF Merge and Split Unregistered Versionrine - http://www.simpopdf.com comes in many forms: solid pellets, granular, or powder. It change in pH, a dimensionless number. is administered using an erosion feeder that is installed in paral5. Total dissolved solids—a measure of the total dissolved lel with the filter and works on the differential pressure across solids in the water, measured in ppm. the filter. 6. Calcium Saturation Index (CSI) or Langelier’s Index—a Caution: Two types of dry chlorine, sodium hypochlorite dimensionless number. and calcium hypochlorite, are both currently used. If these two 7. Cyanuric acid level—Cyanuric acid is used to prevent the compounds are mixed together, a violent explosion can result. dissipation of chlorine by sunlight. It is also toxic at higher Chlorine use varies from 1 to 5 oz/day/1000 gal (0.03 to 0.15 L/ levels. Measured in ppm. day/3785.4 L), depending on the temperature of the water and Engineered systems include: the amount of sunlight. Both warm water and sunlight dissipate 1. Mechanical filtration—sand or cartridge filters, which chlorine rapidly. remove particulates from the water. Ozone is an excellent method of disinfection for water but 2. Disinfection systems—including chlorine and bromine feed- does have limitations. The ozone gas should be applied in a contact tank and the off gas from the tank should be directed to an ers and ozone. Provide control of organics and algae. unoccupied area. In addition, ozone does not leave a residual 3. pH control systems—gaseous CO2 contact tanks and acid/ in the water. A small chlorine feeder should be added to pools base feeders. receiving a high organic load, such as outdoor pools. As a final 4. Oxidation reduction potential (ORP) monitors—provide an note, certain manufacturers will not warranty their products for overall measure of the cleanliness of the water. use in an ozone-treated pool. Operator-administered treatments include: Makeup-Water System 1. Water chemistry—Although some chemistries can be done The fountain should be provided with both a manual and electronically, most must be done by the operator and the an automatic fill system piped in parallel (see Figure 8). The data recorded. manual fill line should be at least 1½ to 2 in. (40 to 50 mm) and 2. Shock or hyperchlorination—used to destroy chloramines the automatic fill line be ¾ in. (20 mm) for small and medium formed when chlorine destroys organic compounds in the fountains and as large as 4 in. (100 mm) for large fountains. A water. Chloramines give pools that distinctive chlorine good rule is to determine the makeup-water rate for cooling smell. A massive dose of chlorine (10 ppm) will destroy the towers in the area. The information should be in gpm (L/min) chloramines. of makeup water per gpm (L/min) of condenser water. This will 3. Dechlorination—After shock treatments, the water is often translate directly to gpm (L/min) of makeup water per gpm (L/ dechlorinated with sodium thiosulfate. min) of effect water. For reflecting pools, the local water authority should have information regarding evaporation rates from 4. pH adjustment—Different chlorine compounds will either swimming pools. When designing the makeup-water system, it raise or lower the pH. Gaseous chlorine (rarely used) will lower the pH and soda ash will need to be added. Powdered may be advantageous to connect the makeup-water line to the filter-pump suction line. If this is done, make sure that there are or liquid chlorine will raise the pH and muriatic acid will no valves between the makeup-water inlet and the pool. This is have to be added. Although proper water chemistry is important from a disinfec- to ensure that the filter system does not become pressurized to tion standpoint, resulting in an algae-free pool, water balance is domestic-water line pressure. Most pool equipment is not built equally important. The Calcium Saturation Index or Langlier’s to withstand the higher pressure. Index is a measure of the corrosiveness of the water. If the CSI is below 0, the water is corrosive and will start to corrode the pool walls, fittings, and equipment. If the CSI is above 0, the water is saturated and will begin to plate out calcium deposits on the pool wall, fittings and equipment. Disinfection in reflecting pools is necessary to control algae and to destroy organics in the water. Common methods of disinfection are chlorine, bromine, and ozone. Chlorine can be used indoors or out with equal success. If used outdoors, the chlorine should be combined with cyanuric acid as a stabilizer. The cyanuric acid will enable the chlorine to last much longer in direct sunlight. Bromine is not recommended for outdoor pools because there is currently no way to stabilize it and it dissipates rapidly. Chlorine comes in three forms: gaseous, liquid, and solid. Gaseous chlorine is the most efficient method of delivery but can be very dangerous when mishandled. Liquid chlorine is the preferred method when dealing with multiple bodies of water or a single body of water in excess of 75,000 gal (283 905 L). A chemical proportioning pump and 50-gal (189.27-L) chlorine solution tank is used to administer the disinfectant. The injec72 Plumbing Systems & Design

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Figure 8 Makeup-Water Devices

In all cases, backflow preventers are required on makeup-water piping to float valves. They are also required on solenoid-operated, makeup lines unless the inlet pipe is at least 2 pipe diameters or more above the pool wall. Verify all methods of backflow prevention with the local authority having jurisdiction. Multilevel pools require that a water-level sensor (not a float valve) be located in the lowest pool and the makeup inlet be located in the highest pool. Low-water cutoff sensors are required in the lowest pool and, if the underwater lights do not have individual low-water cutoffs, then every pool level must have a low-water cutoff. PSDMAGAZINE.ORG

Makeup-Water Devices Figure 9 Electronic Makeup-Water Device Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Stilling wells or chambers Stilling wells or chambers are an important part of any makeup-water system. With a stilling well, the level in the well is an accurate representation of the level in the pool. The advantage to the stilling well is that it remains relatively calm inside the well and does not reflect the surface disturbances that may occur in the pool itself. A stilling well can also incorporate an overflow drain. Mechanical methods Mechanical water makeup is the cheapest method and is least prone to maintenance problems. In this method, a float valve installed in the wall of the pool provides automatic makeup. The top of the pool water must be at least 5 in. above the water level for the float box to fit in the pool wall. A method of remotely maintaining the water level is to install a float valve in an open tank or connected to the pool by a pipe and rooted to a remote location. There should be no connection to this pipe except for a valved drain. With the pipe open at either end, the water level in the tank will be the same as the water level in the pool. The problem encountered with this be 2 in. If the makeup-water line is larger than 1 in., increase the size of the overflow drain to prevent flooding. Sizing for an application is finding a location for the tank. Another method, commonly used on large pools, uses a pilot- outdoor pool should be based on the area of the pool, in ft2 (m2), operated makeup valve. With this method, a small float valve is as required by the local plumbing code for storm drainage. The preferred location for an overflow drain is in the pool installed in a stilling well and the pilot water for the larger valve is routed through it. When the level drops, the pilot float valve opens wall, because it is less obtrusive there. There are times though and water is allowed to open the larger valve. The advantage to this when the pool wall is insufficient for the installation of an overmethod is that a small stilling chamber can be located near the flow drain. In such cases, a removable overflow standpipe can pool while the larger valve can be located near the pumps in the be provided. A dome or screen should be placed on top of the standpipe. The overflow drain also acts as the main drain when mechanical room. Electrical method Where the above methods cannot be the standpipe is removed. Overflow standpipes are subject to used, water makeup can be provided by using electrical sensors vandalism and should be located so that they are not easily that open or close a solenoid valve on the makeup-water line. A accessible to the public. Another method is to install an overmanual fill valve is ordinarily installed in a bypass around the flow pipe on a bypass around a main drain valve. The overflow solenoid valve. The sensors use low voltage or induced voltage pipe invert must be slightly higher than the high water level and that precludes any electrical danger. Sensors that utilize a reed have an air opening to prevent siphonage. switch, activated by a permanent magnet, are also available. The Emergency drains Emergency drains are needed to drain sensors can be mounted in the wall of the pool, accessible from the pool if the outside temperature drops below freezing. This is the front. (See Figure 9.) They can also be located in the top of achieved by providing an aquastat that controls a solenoid valve the wall with the sensors hanging down into a 1¼-in. (32-mm) located in the drain line. The aquastat should be set to open the brass pipe that has an air vent and a horizontal leg extending solenoid valve if the temperature drops too low. The solenoid into the pool water. Where it is not feasible to mount the sensors valve must have a manual override in the event of a power failure in the pool wall, they can be located anywhere in the pool water and must not require differential pressure to open the valve. An by mounting the sensor box on top of a brass conduit wherever Ongontz valve is another emergency drain valve that mechaniit enters the pool. The sensor will generate a small amount of cally starts to open when the temperature drops to 38°F (3.33°C) current from the sensor tip, through the water and into the brass and fully opens at 34°F (1.11°C). In the above cases, electrical pipe. If water is not present, the current flow stops and the con- sensors, as described above under “Makeup-Water Devices,” trol panel opens the solenoid valve. Brass piping must be used should be provided to shut off the electrical power to the pumps as it provides the electrical ground path. Electrical wiring has and lights. The makeup-water valve should be wired to close if to be extended to the sensors in the pool area as well as to the the emergency drain valve is open. It may also be advisable to have an alarm ring to indicate that the emergency drain valve control panel and the solenoid valve. Dual sensors are available that will provide for water makeup has opened. ✺ and low-water cutoff (so that pumps will be shut off in the event References of low water level). They can also shut off the underwater lights, 1. American National Standards Institute/National Spa and which can be damaged by operation without adequate water Pool Institute. 1991. Standard for public swimming pools, cover. ANSI/NSPI-1 1991. Alexandria, VA: National Spa and Pool Overflow and Drainage System Institute. Overflow drains Overflow drains are required for two rea- 2. Kowalsky, L. 1990. Pool/spa operators handbook. San Antosons: to provide a means to remove water if the makeup-water nio, TX: National Swimming Pool Foundation. valve malfunctions and to provide a means to remove storm 3. Tchobanoglous, George, and Franklin L. Burton. 1991. water and maintain a fixed water level so that nozzles will work Wastewater engineering: Treatment, disposal, and reuse. 3d properly. The size of an overflow drain for an indoor pool should ed. New York: McGraw-Hill. MAY/JUNE 2006



Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PS&D), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status. ASPE features a technical article in every issue of PS&D, excerpted from its own publications. Each article is followed by a multiplechoice test and a simple reporting form. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of 90% or higher on the test, you will be notified that you have logged 0.1 CEU, which can be

applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years. No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PS&D within the past 12 months. However, CEU credit only can be obtained on a total of eight PS&D articles in a 12-month period. Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

CE Questions—“Reflecting Pools and Fountains” (PSD 133) 1. The filtration turnover rate in a reflecting pool or fountain is determined by _______. a. the local code b. the architect c. the engineer d. the color of the water desired 2. Surge collars are used to minimize _______ in circular pools. a. discoloration b. plant growth c. evaporation d. waves 3. The water treatment system should maintain _______. a. sparkling clean water b. odor-free water c. an algae-free pool d. all of the above 4. When a fountain is to be operated in freezing conditions, the water should be heated to maintain _______ degrees Fahrenheit minimum. a. 10 b. 35 c. 40 d. all of the above 5. The University of Illinois and the University of Florida have determined that the smooth holes found in underground PVC pipe are caused by _______. a. exposure to ultraviolet rays b. exposure to sunlight c. termites d. high velocity 6. The headers indicated in Fig. 5 may have their orifices balanced using _______. a. equations 1 through 5 b. the average percentage indicated c. good engineering practice d. looped piping around the fountain


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7. All pumps serving the pool and/or fountain should be located to ensure _______. a. they are higher than the pool or fountain for maintenance purposes b. they are lower than the pool or fountain to maintain a flooded suction line c. that they can be viewed by the public d. none of the above 8. The most common types of weirs are _______. a. metal edge b. upward tapered c. rounded edge d. all of the above 9. Oxidation reduction potential (ORP) is _______. a. controlled by the pH b. a measure of the total dissolved solids in water c. controlled by the operator d. a measure of the cleanliness of the water 10. Reflecting pools and fountains provide _______. a. a place to grow water plants b. a retreat area in which to rest and relax c. a place to fish d. a place for frogs to play 11. Hydraulic balancing of the suction and return headers is required _______. a. to ensure even flow throughout the fountain b. by local codes c. to keep sound levels low d. all of the above 12. When using a sand filter, what flow rate and above, in gallons per minute, will classify it as a high-rate filter? a. 2 gpm b. 4 gpm c. 8 gpm d. 10 gpm

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Signature Expiration date: Continuing education credit will be given for this examination through May 31, 2007. Applications received after that date will not be processed.



Expiration date

Signature

Reflecting Pools and Fountains (PSD 133)





Reflecting Pools and Fountains (PSD 133) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

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PSD 139

Private Sewage Disposal Systems Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson

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Private Sewage Disposal Systems


With the ever-increasing cost of land located in proximity to urban centers, more and more construction is being implemented in outlying areas. Sanitary sewers are not usually available in these remote locations and it becomes necessary for the plumbing engineer to design private sewage systems to handle the wastes from buildings. Before the rapid escalation of land values, most private sanitary disposal systems were used almost exclusively for private residences. It is estimated that 15 million such systems are presently in use in the United States. Of greater significance, roughly 25% of all new home construction now employs the septic tank–soil absorption sewage disposal system. Where the concentration of population is not sufficient to economically justify the installation of public sewer systems, installation of a septic tank in conjunction with a subsurface soil absorption field has proven to be an exceptionally satisfactory method of sewage disposal. When properly designed, installed, operated, and maintained, it compares very favorably with the most sophisticated municipal sewage treatment plants. In 1946, the U.S. Public Health Service, in cooperation with other federal agencies involved in housing, embarked upon a five-year study to establish criteria for the design, installation, and maintenance of the septic tank. Most of the information in this chapter is freely drawn from that study and a later report issued in 1967.

Sewage System Criteria The proper disposal of sewage is a major factor affecting the health of the public. When improper or inadequate disposal of sewage occurs, many diseases, such as dysentery, infectious hepatitis, typhoid, paratyphoid, and various types of diarrhea are transmitted through contamination of food and water. To avoid such hazards, any system of sewage disposal must meet the following criteria: • It must not contaminate any drinking water supply. • It must not be accessible to insects, rodents, or other possible carriers that might come in contact with food or drinking water. • It must not be accessible to children. • It must not violate laws or rules and regulations governing water pollution or sewage disposal. • It must not pollute or contaminate the waters of any bathing beach, shellfish breeding ground, or any stream used for public or private water supply or for recreational purposes. • It must not become malodorous or unsightly in appearance. All these criteria are admirably fulfilled by a public sewage disposal system. Every effort should be made to utilize such facilities if at all possible. When public sewers are not available, some other satisfactory method must be employed.

Any method of sewage disposal is merely an attempt to complete the hydrologic cycle, or as it is now popularly called, the ecological cycle. Contaminated water (wastes) of undesirable quality is received and, after processing, returned at an acceptable level of quality. The systems to be discussed are those that return the waste water to the soil and ultimately to the ground water (water table). There are presently two systems that return waste water to the soil. They are the cesspool and the septic tank–soil absorption systems.

Cesspools A cesspool is nothing more than a covered pit with an openjointed or perforated lining into which raw sewage is discharged. The liquid portion of the sewage is disposed by seepage or leaching into the porous soil surrounding the cesspool. The solids (sludge) are retained in the pit. A cesspool finds its greatest application in receiving the effluent from one-family homes and it is not recommended even for this use. The raw sewage tends to seal the openings in the pit lining as well as the surrounding soil, thus necessitating frequent visits from the “honey dippers” (cesspool cleaning services). Cloggage may become so severe that complete abandonment of the existing cesspool and the construction of a new pit is often necessary. A cesspool should never be recommended as a substitute for a septic tank with a soil absorption field. A seepage pit (discussed in another portion of this chapter) should never be confused with a cesspool. Although the construction is the same for both, a seepage pit receives the effluent from a septic tank (where the solids have been liquified), whereas a cesspool receives raw sewage.

Septic Tanks A septic tank is a liquid-tight structure, with inlet and outlet connections, which receives raw sewage. It is basically a sewage settling tank in which raw sewage is retained for a specified period of time, usually 24 hr. The primary purpose of the septic tank is to act as a settling tank and to break up solids so that the resulting effluent will not clog the pores of the soil in the leaching field. Very little purification is accomplished in the tank; the actual treatment and digestion of harmful waste materials takes place in the ground after discharge from the tank. Three functions are performed by a septic tank to produce an effluent suitable for acceptance by a subsoil absorption system of sewage disposal: (1) removal of solids, (2) biological treatment, and (3) sludge and scum storage. Removal of Solids Clogging of the soil varies directly with the amount of suspended solids in the liquid. The rate of flow entering the septic tank is reduced within the tank so that solids sink to the bottom or rise to the surface of the liquid in the tank. These solids are retained and the clarified effluent is discharged.

Reprinted from Engineered Plumbing Design II, Chapter 21: “Private Sewage Disposal Systems,” by A. Calvin Laws, PE, CPD. © American Society of Plumbing Engineers. Plumbing Systems & Design

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Solids and liquid in the tank are exposed to bacterial and Simpo PDF Merge and Split Unregistered Version natural processes, which decompose them. The bacteria present in the wastes are of the anaerobic type, which thrives in the absence of oxygen. Decomposition of the sewage under anaerobic conditions is termed “septic” and it is from this the tank derives its name. After such biological action, the effluent causes less clogging of the soil than untreated sewage containing the same quantity of suspended solids. Sludge and Scum Storage Sludge is an accumulation of solids at the bottom of the tank. Scum is a partially submerged floating mat of solids that forms at the surface of the liquid in the tank. The sludge is digested and compacted into a smaller volume. The same action occurs with the scum but to a lesser degree. Regardless of the efficiency of the operation of the septic tank, a residual of inert solid material will always remain. Adequate space must be provided in the tank to store this residue during the intervals between cleanings. Sludge and scum will flow out of the tank with the effluent and clog the disposal field in a very short period of time if pumping out of the residue is not performed when required. Septic tanks are eminently effective in performing their purpose when adequately designed, constructed, operated, and maintained. They do not accomplish a high degree of bacteria removal. Although the sewage undergoes some treatment in passing through the tank, infectious agents present in the sewage are not removed. The effluent of a septic tank cannot be considered safe. In many respects, the discharged liquid is more objectionable than the influent because it is septic and malodorous. This should not be construed in any way as detracting from the value of the tank because its primary purpose is simply to condition the raw sewage so that it will not clog the disposal field. Continued treatment and the removal of pathogens are accomplished by percolation through the soil. Disease-producing bacteria will die out after a time in the unfavorable environment of the soil. Bacteria are also removed by physical forces during filtration through the soil. This combination of factors achieves the eventual purification of the septic tank effluent. Septic Tank Location The location of the septic tank should be chosen so as not to cause contamination of any well, spring, or other source of water supply. Underground contamination can travel in any direction for considerable distances unless effectively filtered. Tanks should never be closer than 50 ft to any source of water supply and, where possible, greater distances are preferable. They should be located where the largest possible area will be available for the disposal field and should never be located in swampy areas subject to flooding. Ease of maintenance and accessibility for cleaning are important factors to be considered. When it is anticipated that public sewers will be available in the future, provisions should be made for the eventual connection of the house sewer to such a public source. Tank Capacity Studies have proven that liberal tank capacity is not only desirable from a functional viewpoint but is good economical design practice. The liquid capacities recommended in Table 1 make allowances for all household appliances including garbage grinders.

Table 1 Liquid Capacity of Tank (gal)

- http://www.simpopdf.com (provides for use of garbage grinders, automatic clothes washers, and other household appliances)

Recommended Equivalent Number of Minimum Tank Capacity per Bedrooms Capacity Bedroom 2 or less 750 375 3 900 300 4a 1000 250 a For each additional bedroom, add 250 gal.

Tank Material Septic tanks must be watertight and constructed of materials not subject to excessive corrosion or decay. Acceptable materials are concrete, coated metal, vitrified clay, heavyweight concrete blocks, or hard-burned bricks. Properly cured precast and cast-in-place, reinforced concrete are believed to be acceptable everywhere. Local codes should be checked as to the acceptability of the other materials. Steel tanks conforming to U.S. Department of Commerce Standard 177-62 are generally acceptable. Precast tanks should have a minimum wall thickness of 3 in. and should be adequately reinforced to facilitate handling. When precast slabs are used as covers, they should be watertight, at least 3 in. thick and adequately reinforced. All concrete surfaces should be coated with a bitumastic paint or similar compound to minimize corrosion. Tank Access Access should be provided to each compartment of the tank for cleaning and inspection by means of a removable cover or a 20in. minimum size manhole. When the top of the tank is more than 18 in. below grade, manholes and inspection holes should be extended to approximately 8 in. below grade. They can be extended to grade if a seal is provided to prevent the escape of odors. Tank Inlet The invert elevation of the inlet should be at least 3 in. above the liquid level in the tank. This will allow for momentary surges during discharge from the house sewer into the tank and also prevent the backup and stranding of solids in the piping entering the tank. A vented inlet tee or baffle should be provided to direct the influent downward. The outlet of the tee should terminate at least 6 in. below the liquid level but in no case should it be lower than the bottom of the outlet fitting or device. Tank Outlet The outlet fitting or device should penetrate the liquid level just far enough to provide a balance between the sludge and scum storage volumes. This will assure usage of the maximum available tank capacity. A properly operating tank divides itself into three distinct layers: scum at the top, a middle layer free of solids (clear space), and sludge at the bottom layer. While the outlet tee or device retains the scum in the tank, it also limits the amount of sludge that can be retained without passing some of the sludge out with effluent. Data collected from field observation of sludge accumulations indicate that the outlet device should extend to a distance below the liquid level equal to 40% of the liquid depth. For horizontal cylindrical tanks the percentage should be 35. The outlet device or tee should extend up to within 1 in. of the top of the tank for venting purposes. The space between the top of the tank and MAY/JUNE 2007


CONTINUING EDUCATION: Private Sewage Disposal Systems the baffle permits gas to pass through the tank into the building and such additions are not recommended. Some products Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com sanitary system and eventually to atmosphere where it will not that claim to “clean” septic tanks contain sodium hydroxide or cause a nuisance. potassium hydroxide as the active agent. Such compounds may result in sludge bulking and a sharp increase in alkalinity, which Tank Shape may interfere with digestion. The effluent may severely damage Available data indicate that for tanks of a given capacity and the soil structure of the disposal field and cause accelerated depth, the shape of a septic tank is unimportant and that shalclogging even though some immediate temporary relief may be low tanks function equally as well as deep ones. It is recomexperienced shortly after application of the product. mended, however, that the minimum plan dimension be 2 ft On the other hand, ordinary household chemicals in general and the liquid depth range from 30 to 60 in. use around the home will not have a harmful effect on the operScum Storage Space ation of a septic tank. Small amounts of chorine bleach or small Space is required above the level of the liquid in the tank for the quantities of lye or caustic are not objectionable. If tanks are accumulated scum, which floats on top of the liquid. Although sized as recommended herein, the dilution of the lye or causthere is some variation, approximately 30% of the total amount tics in the tank will be enough to minimize any harmful effects. of scum will accumulate above the liquid level and 70% will be Soaps, detergents, bleaches, drain cleaners, etc., will have no submerged. In addition to the scum storage space, 1 in. should appreciable adverse effect on the system. However, since both be provided at the top of the tank for free passage of gas through the soil and the organisms might be susceptible to large doses the tank back to the inlet and building drainage system. of chemicals, moderation is recommended. For tanks with vertical walls, the distance between the top of Toilet paper substitutes, paper towels, newspaper, wrapping the tank and the liquid level should be approximately 20% of the paper, rags, and sticks should not be introduced into the septic liquid depth. For horizontal cylindrical tanks, the liquid depth tank. They may not decompose and are likely to lead to clogging should be 79% of the diameter of the tank. This will provide an of the disposal field. open area at the top of the tank equal to 15% of the total crossBackwash from a household water-softening unit has no sectional area of the tank. adverse effect on the operation of a septic tank, but may cause a slight shortening of life of the disposal field installed in a strucCompartments Although a number of arrangements are possible, compart- tured clay type soil. ments refer to the number of units in series. They can be sepa- Septic Tanks for Nonresidential Buildings rate units connected together or sections enclosed in one con- Table 1 gives the liquid capacity of tanks on the basis of the tinuous shell with watertight partitions separating the individual number of bedrooms. When designing a septic tank for other compartments. types of buildings, Table 2 may be used to estimate the quantity A single-compartment tank gives acceptable performance, of sewage flow. The quantities listed are merely the best averbut available research data indicate that a two-compartment ages presently available and should be modified in localities or tank with the first compartment equal to ½ to 2∕3 of the total establishments where available information indicates a need to volume provides better suspended solids removal. Tanks with do so. three or more equal compartments perform about on an equal basis with a single-compartment tank of the same total capacity. The use of a more than two-compart- Figure 1 Precast Septic Tank ment tank is therefore not recommended. All the requirements of construction stated previously for a single-compartment tank apply to the two-compartment tank. Each compartment should be provided with an access manhole and venting between compartments for the free passage of gas. Figure 1 illustrates all the salient features of a typical two-compartment septic tank. Cleaning of Tanks Before too much sludge or scum is allowed to accumulate, septic tanks should be cleaned to prevent the passage of sludge or scum into the disposal field. Tanks should be inspected at least once a year and cleaned when necessary. Cleaning is usually accomplished by pumping the contents of the tank into a tank truck. A small residual of sludge should be left in the tank for “seeding” purposes. Tanks should never be washed or disinfected after cleaning. Chemical Additives The operation of a septic tank is not improved in any way whatsoever by the addition of chemicals; Plumbing Systems & Design

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The retention period of the sewage in a septic tank should be Subsurface Soil Absorption System Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com 24 hr. Table 2 gives the gallons per person per day (24 hr). The Criteria for Design required liquid capacity of the tank can then be determined by The first step in the design of a subsurface soil absorption multiplying the values given in the table by the estimated popusewage disposal system is to determine whether the soil is suitlation. able for the absorption of the septic tank effluent. If it is, the next Tables 3 and 4 give daily gallonages in terms of fixtures for step is to determine the area required for the disposal field. The country clubs and public parks, respectively. soil must have an acceptable percolation rate and should have adequate clearance from ground water. In general, two criteria must be met: Table 2 Quantities of Sewage Flows Type of Establishment Airports (per passenger) Apartments—multiple family (per resident) Bathhouses and swimming pools Camps: Campground with central comfort stations With flush toilets, no showers Construction camps (semi-permanent) Day camps (no meals served) Resort camps (night and day) with limited plumbing Luxury camps Cottages and small dwellings with seasonal occupancy Country clubs (per resident member) Country clubs (per non-resident member present) Dwellings: Boarding houses additional for non-resident boarders Luxury residences and estates Multiple-family dwellings (apartments) Rooming houses Single-family dwellings Factories (gallons/person/shift, exclusive of industrial wastes) Hospitals (per bed space) Hotels with private baths (2 persons per room) Hotels without private baths Institutions other than hospitals (per bed space) Laundries, self service (gal/wash, i.e., per customer) Mobile home parks (per space) Motels with bath, toilet, and kitchen wastes (per bed space) Motels (per bed space) Picnic parks (toilet wastes only) (per picknicker) Picnic parks with bathrooms, showers, and flush toilets Restaurants (toilet and kitchen wastes per patron) Restaurants (kitchen wastes per meal served) Restaurants, additional for bars and cocktail lounges Schools: Boarding Day, without gyms, cafeterias, or showers Day, with gyms, cafeterias, and showers Day, with cafeterias, but without gyms or showers Service stations (per vehicle served) Swimming pools and bathhouses Theaters: Movie (per auditorium seat) Drive-in (per car space) Travel trailer parks Without individual water and sewer hookups (per space) With individual water and sewer hookups (per space) Workers: Construction (at semi-permanent camps) Day, at schools and offices (per shift)

Table 3 Sewage Flow from Country Clubs Gallons per Day Type of Fixture per Fixture Showers 500 Baths 300 Lavatories 100 Toilets 150 Urinals 100 Sinks 50

Gallons Per Person Per Day (unless otherwise noted) 5 60 10 35 25 50 15 50 100 50 100 25 50 10 150 60 40 75 35 250 60 50 125 50 250 50 40 5 10 10 3 2 100 15 25 20 10 10 5 5 50 100 50 15

Table 4 Sewage Flow at Public Parks (during hours when park is open) Gallons per Day Type of Fixture per Fixture Flush toilets 36 Urinals 10 Showers 100 Faucets 15

1. The percolation rate should be within the range shown in Table 5 or Table 6. 2. The maximum elevation of the groundwater table should be at least 4 ft below the bottom of the trench or seepage pit. Rock formation or other impervious strata should be at a depth of more than 4 ft below the bottom of the trench or seepage pit.

Table 5 Absorption Area Requirements for Individual Residencesa (provides for garbage grinder and automatic clothes washing machines)

Percolation Rate (time required for water to fall 1 in.), in minutes 1 or less 2 3 4 5 10 15 30c, e 45c, e 60c, e, f

Required Absorption Area, in ft2/bedroomb, standard trenchc, seepage bedsc, and seepage pitsd 70 85 100 115 125 165 190 250 300 330

a It is desirable to provide sufficient land area for an entire new absorption system if needed in the future. b In every case, sufficient land area should be provided for the number of bedrooms (minimum of two) that can be reasonably anticipated, including the unfinished space available for conversion as additional bedrooms. c Absorption area is figured as trench bottom area and includes a statistical allowance for vertical side wall area. d Absorption area for seepage pits is figured as effective side wall area beneath the inlet. e Unsuitable for seepage pits if over 30. f Unsuitable for absorption systems if over 60

Table 6 Allowable Rate of Sewage Application to a Soil Absorption System Percolation Rate Maximum Rate of Sewage Application (time for water to fall (gal/ft2/day)a for Absorption Trenchesb, 1 in.), in minutes Seepage Beds, and Seepage Pitsc 1 or less 5.0 2 3.5 3 2.9 4 2.5 5 2.2 10 1.6 15 1.3 30d 0.9 45d 0.8 60d, e 0.6 a Not including effluents from septic tanks that receive wastes from garbage grinders and automatic washing machines. b Absorption area is figured as trench bottom area, and includes a statistical allowance for vertical sidewall area. c Absorption area for seepage pits is effective sidewall area. d Over 30 unsuitable for seepage pits. e Over 60 unsuitable for absorption systems. MAY/JUNE 2007


CONTINUING EDUCATION: Private Sewage Disposal Systems If these two primary conditions cannot be met, the site is Simpo PDF Merge and Split Unregistered Version unsuitable for a soil absorption system and some other seepage disposal system must be employed. Percolation Tests Percolation tests help to determine the acceptability of the site and establish the size of the disposal system. The length of time required for percolation tests varies for different types of soil. The safest method is to make tests in holes that have been kept filled with water for at least 4 hrs and preferably overnight. Percolation rates should be determined on the basis of test data obtained after the soil has had the opportunity to become wetted or saturated. Enough tests should be made in separate holes to assure the validity of results. The percolation test as developed at the Robert A. Taft Sanitary Engineering Center has proven to be one of the best in the country and is given here in its entirety: Procedure for Percolation Tests 1. Number and Location of Tests. Six or more tests shall be made in separate test holes spaced uniformly over the proposed absorption field site. 2. Type of Test Hole. Dig or bore a hole, with horizontal dimensions of from 4 to 12 in. and vertical sides to the depth of the proposed absorption trench. In order to save time, labor, and volume of water required per test, the holes can be bored with a 4-in. auger. 3. Preparation of a Test Hole. Carefully scratch the bottom and sides of the hole with a knife blade or sharp-pointed instrument, in order to remove any smeared soil surfaces and to provide a natural soil interface into which water may percolate. Remove all loose material from the hole. Add 2 in. of coarse sand or fine gravel to protect the bottom from scouring and sediment. 4. Saturation and Swelling of the Soil. It is important to distinguish between saturation and swelling. Saturation means that the void spaces between soil particles are full of water. This can be accomplished in a short period of time. Swelling is caused by intrusion of water into the individual soil particle. This is a slow process, especially in clay-type soil, and is the reason for requiring a prolonged soaking period. In the conduct of the test, carefully fill the hole with clear water to a minimum depth of 12 in. over the gravel. In most soils, it is necessary to refill the hole by supplying a surplus reservoir of water, possibly by means of an automatic syphon, to keep water in the hole for at least 4 hrs and preferably overnight. Determine the percolation rate 24 hrs after water is first added to the hole. This procedure is to ensure that the soil is given ample opportunity to swell and to approach the condition it will be in during the wettest season of the year. Thus, the test will give comparable results in the same soil, whether made in a dry or wet season. In sandy soils, containing little or no clay, the swelling is not essential, and the test may be made as described under item 5C, after the water from one filling of the hole has completely seeped away. 5. Percolation Rate Measurement. With the exception of sandy soils, percolation rate measurements shall be made on the day following the procedure described under item 4, above. Plumbing Systems & Design

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A. If water remains in the test hole after the overnight

- http://www.simpopdf.com swelling period, adjust the depth to approximately 6 in. over the gravel. From a fixed reference point, measure the drop in water level over a 30-min. period. This drop is used to calculate the percolation rate. B. If no water remains in the hole after the overnight swelling period, add clear water to bring the depth of water in the hole to approximately 6 in. over the gravel. From a fixed reference point, measure the drop in water level at approximately 30-min intervals for 4 hrs, refilling 6 in. over the gravel as necessary. The drop that occurs during the final 30-min period is used to calculate the percolation rate. The drops during prior periods provide information for possible modification of the procedure to suit local circumstances. C. In sandy soils (or other soils in which the first 6 in. of water seeps away in less than 30 min, after the overnight swelling period), the time interval between measurements shall be taken as 10 min and the test run for 1 hr. The drop that occurs during the final 10 min is used to calculate the percolation rate.

Absorption Area For locations where the percolation rates and soil characteristics prove to be satisfactory, the next step is to determine the required absorption area from Table 5 for residences or from Table 6 for other types of buildings. As noted in the tables, soil in which the percolation rate is slower than 1 in. in 30 min is not suitable for seepage pits and a rate slower than 1 in. in 60 min is not satisfactory for any type of soil absorption system. There are three types of soil absorption systems: 1. Absorption trenches 2. Seepage beds 3. Seepage pits. The selection of the system will be affected by the location Table 7 Minimum Distance Between Components of Sewage Disposal System Horizontal Distance (ft) Component of Well or Water Supply Stream Dwelling Property System Suction Line Line (pressure) Line Building sewer 50 10a 50 — — Septic tank 50 10 50 5 10 Disposal field 100 25 50 20 5 and seepage bed Seepage pit 100 50 50 20 10 Cesspoolb 100 50 50 20 15 a Where the water supply line must cross the sewer line, the bottom of the water service within 10 ft of the point of crossing shall be at least 12 in. above the top of the sewer line. The sewer line shall be of cast iron with leaded or mechanical joints at least 10 ft on either side of the crossing. b Not recommended as a substitute for a septic tank. To be used only when found necessary and approved by the health authority.

of the system in the area under consideration. A safe distance must be maintained between the site and the source of any water supply. No specific distance can be absolutely safe in all localities because of the many variables involved in the underground travel of pollution. Table 7 can be used as a guide for establishing minimum distances between various components of a sewage disposal system. Seepage pits should never be installed in areas of shallow wells or where there are limestone formations and sinkholes PSDMAGAZINE.ORG

with connection to underground channels through Figure 2 Section through Typical Absorption Trench Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com which pollution could travel to water sources. Absorption Trenches The drain pipe for a soil absorption field may be 12-in. lengths of 4-in. agricultural drain tile, 2–3 ft lengths of open-joint vitrified clay sewer pipe, or perforated nonmetallic pipe. Individual laterals should not exceed 100 ft in length and the trench bottom and piping should be level. Use of more and shorter laterals is recommended because if a breakdown should occur in any one lateral, most of the field would still be operative. The space between laterals should be at least twice the depth of gravel to prevent overtaxing the percolative capacity of the adjacent soil. The depth of the absorption trenches should be at least 24 in. to provide the minimum required gravel depth and earth cover. Additional depth may be required for ground contour adjustment, for extra aggregate specified under the pipe, or for other design purposes. The minimum distance of 4 ft between the bottom of the trench and the water table is essential to minimize groundwater contamination. Freezing is an extremely rare occurrence in a well-constructed system that is kept in continuous operation. It is of course extremely important that the pipe be completely surrounded by the gravel to provide for free movement of the waste water. The required absorption area is based upon the results of the percolation tests and may be selected from Table 5 or 6.

Example 1 For a three-bedroom house and a percolation rate of 1 in. in 15 min, the necessary absorption area will be 3 bedrooms × 190 ft2 per bedroom (Table 5) = 570 ft2. For 2-ft-wide trenches with 6 in. of gravel below the drain pipe the total length of trench will be: 570 ÷ 2 = 285 ft. If this length is divided into three portions (3 laterals), the length of each lateral will be 285 ÷ 3 = 95 ft. If this length is too long for the site, the number of laterals must be increased. Using 5 laterals, the length of each lateral will be 57 ft. If the trenches are separated by 6 ft, the width of the field will be 2-ft-wide trenches × 5 trenches = 10 ft plus 6 ft between trenches × 4 spaces = 24 ft. The total field will then be 57 ft in length by 34 ft. in width for a total area of 1938 ft2 plus the additional land required to keep the field an acceptable distance from property lines, wells, etc. Construction Careful construction is extremely important in achieving a satisfactory soil absorption system. Care must be exercised so as not to seal the surfaces on the bottom and sides of the trenches. Trenches should not be excavated when the soil is wet enough to smear or compact easily. Open trenches should always be protected from surface runoff to prevent entrance of silt and debris. All smeared or compacted surfaces should be raked to a depth of 1 in. and loose material removed before placing gravel in the trench. The pipe should be completely surrounded by clean, graded gravel ranging in size from ½ to 2½ in. Cinders, broken shells, or similar materials are unsuitable as they are too fine and will lead to premature clogging of the soil. The gravel should extend at least 2 in. above the top of the pipe, at least 6 in. below the bottom of the pipe and fill the entire width of the trench. The top

of the gravel should be covered with untreated building paper or a 2-in. layer of hay, straw, or similar pervious material to prevent the earth backfill from clogging the gravel. If an impervious covering is used, it will interfere with evapotranspiration at the surface. This is an important factor in the operation of a disposal field and, although evapotranspiration is not generally taken advantage of in the calculations, it provides an added factor of safety. If tile pipe is used, the upper half of the joint openings should be covered. Drain tile connectors, collars, clips or other spacers with covers for the upper half of the joints may be used to assure uniform spacing, proper alignment, and protection of the joints. They are available in galvanized iron, copper, and plastic. The problem of root penetration can be avoided by the use of a liberal quantity of gravel around the pipe. There should be at least 12 in. of gravel beneath the pipe when a trench is within 10 ft of large trees or dense shrubbery. Backfilling of the trench should be hand tamped and the trench should be overfilled at least 4 to 6 in. This will prevent settlement to a point lower than the surface of the adjacent ground where storm water could collect and cause premature saturation of the absorption field and possible complete washout of the trench. Machine tamping or hydraulic backfilling should never be permitted. Figure 2 illustrates a typical absorption trench. Seepage Beds The use of seepage beds in lieu of standard trenches has been around for over twenty-five years. Common design practice for soil absorption fields is for trenches with widths varying from 12 to 36 in. When trenches are wider than 3 ft they are called seepage beds. Typically rectangular in shape, seepage beds are compact and used when less land is available for system design. Dry climates prove to be a better environment for use than climates having wet, humid conditions. Keep in mind, seepage beds do not have the sidewall area to provide oxygen to the center of a bed and long-term performance depends on the condition of the sidewall area. Slopes greater than 5% are not suitable for this absorption system application. Care must be taken during conMAY/JUNE 2007


CONTINUING EDUCATION: Private Sewage Disposal Systems struction so as not to destroy soil structure by compacting the equal distribution. Rather, they probably act as diversion Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com soil in the bottom of the bed. Additionally, the Federal Builddevices sending most of the liquid to part of the system. ing Administration has sponsored studies indicating that seepBecause of the above findings, it is recommended that distriage beds are a satisfactory method for disposing of the effluent bution boxes be eliminated in all disposal field systems where from septic tanks in soils that are satisfactory for soil absorp- they are not specifically required by local codes. tion systems. The studies have demonstrated that the empirical Seepage Pits relationship between percolation tests and the bottom area of Where absorption fields are impractical, seepage pits may be trenches is applicable for the design of seepage beds. applicable. The capacity of a seepage pit should be computed The three main elements of a seepage bed are the same as those on the basis of percolation tests made in each vertical stratum of trenches: penetrated. The weighted average of the results should be used 1. The absorption surface to obtain the design figure. Soil strata in which percolation rates 2. The gravel layer are in excess of 30 min/in. should not be included in computing 3. The distribution system. the absorption area. The advantages of seepage beds are (1) a wide bed makes more efficient use of land than a series of long narrow trenches with Effective Area of Seepage Pit wasted land between the trenches and (2) efficient use can be The effective area of a seepage pit is the vertical wall area of the made of a variety of modern earth-moving equipment already pervious ground below the inlet. The area of the bottom of the pit is not considered in calculating the effective area nor is any at the site, which will result in lower costs for the system. impervious vertical areas. Table 8 is a compilation of vertical Design Criteria for Seepage Beds surface area for various pit diameters and depths. The bottom of The following criteria should be adhered to in the design of the pit must always be at least 4 ft above groundwater table. seepage beds: 1. The amount of bottom absorption area Table 8 Vertical Wall Areas of Seepage Effective Strata Depth Below Flow Line (below inlet) shall be the same as for trenches, shown in Table 5 or 6. Diameter of seepage pit (feet) 1 foot 2 feet 3 feet 4 feet 5 feet 6 feet 7 feet 8 feet 9 feet 10 feet 2. Percolation tests should be performed as 3 9.4 19 28 38 47 57 66 75 85 94 previously outlined. 4 12.6 26 38 50 63 75 88 101 113 126 3. The bed should have a minimum depth 5 15.7 31 47 63 79 94 110 126 141 157 6 18.8 38 57 75 94 113 132 151 170 188 of 24 in. to provide a minimum earth 7 22.0 44 66 88 110 132 154 176 198 220 backfill cover of 12 in. 8 25.1 50 75 101 126 151 176 201 226 251 4. The bed should have a minimum of 12 9 28.3 57 85 113 141 170 198 226 251 283 10 31.4 63 94 126 157 188 220 251 283 314 in. depth of gravel extending at least 2 in. 11 34.6 69 101 138 173 207 212 276 311 346 above and 6 in. below the pipe. 12 37.7 75 113 151 188 226 264 302 339 377 5. The bottom of the bed and the distribuExample: A pit of 5-foot diameter and 6-foot depth below the inlet has an effective area of 94 square feet. A pit of 5-foot diameter and tion tile or perforated pipe should be 16-foot depth has an area of 94 + 157, or 251 square feet. level. 6. The drain lines for distributing the effluWhen more than one pit is required to obtain the necessary ent from the septic tank should be spaced no greater than 6 absorption area, the distance between the walls of adjacent pits ft apart and no greater than 3 ft from the bed sidewalls. should be equal to three times the diameter of the largest pit. Distribution Boxes For pits 20 ft or greater in depth the minimum spacing between Although many codes specifically require the use of a distribu- walls should be 20 ft. tion box in a soil absorption system, research and field tests Construction of Seepage Pit have conclusively demonstrated that they offer practically no All loose material should be removed from the excavated advantages and can be a source of serious problems in many pit. The pit should be backfilled with clean gravel to a depth installations. As a result of its study of distribution boxes, the of 1 ft above the pit bottom to provide a sound foundation for Public Health Service set forth the following conclusions in the the pit lining. Material for the lining may be clay or concrete report to the Federal Housing Administration: brick, block, or rings. Rings should have weepholes or notches 1. Distribution boxes can be eliminated from septic tankto provide for seepage. Brick and block should be laid dry with soil absorption systems in favor of some other method of staggered joints. Brick should be laid flat to form a 4-in. wall. distribution without inducing increased failure of disposal The outside diameter of the lining should be 12 in. less than the fields. In fact, evidence indicates that distribution boxes as diameter of the pit to provide a 6-in. annular space between presently used may be harmful to the system. the lining and pit wall. This annular space should be filled with 2. Data indicate that on level ground, equal distribution is clean, coarse gravel to the top of the lining. not necessary if the system is designed so that an overload Flat concrete covers are recommended. They should be suptrench can drain back to the other trenches before failure ported by undisturbed earth and extend at least 12 in. beyond occurs. the excavation. The cover should not bear on the lining for sup3. On sloping ground a method of distribution is needed to port. A 9-in. capped opening in the pit cover is convenient for pit prevent excessive buildup of head and failure of any one inspection. All concrete surfaces should be coated with a bitutrench before the capacity of the entire system is utilized. mastic paint or similar product to minimize corrosion. It is doubtful that distribution boxes as presently used give Plumbing Systems & Design

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All connecting piping should be laid on a firm bed of undisSimpo PDF Merge and Split Unregistered Version turbed soil throughout their length and at a minimum grade of 2% (¼ in./ft). The pit inlet pipe should extend at least 1 ft into the pit with a tee or ell to direct the flow downward to prevent washing and eroding of the sidewalls. When more than one pit is utilized they should be connected in series. ✺


MAY/JUNE 2007



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The May/June 2007 continuing education article is “Private Sewage Disposal Systems,” Chapter 13 of Engineered Plumbing Design II by A. Cal Laws, PE, CPD. With the ever-increasing cost of land located in proximity to urban centers, more and more construction is being implemented in outlying areas. Sanitary sewers are not usually available in these remote locations and it becomes necessary for the plumbing engineer to design private sewage systems to handle the wastes from buildings. Where the concentration of population is not sufficient to economically justify the installation of public sewer systems, installation of a septic tank in conjunction with a subsurface soil absorption field has proven to be an exceptionally satisfactory method of sewage disposal. This chapter explains the different types of private sewage disposal systems for residential and commercial applications as well as criteria for their design and construction. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Private Sewage Disposal Systems” (PSD 139) 1. The retention period of sewage in a septic tank should be _________. a. 12 hours, b. 24 hours, c. 36 hours, d. 48 hours 2. The first step in the design of a subsurface soil absorption sewage disposal system is _________. a. ascertain the code requirements b. determine the area required for the disposal field c. determine whether the soil is suitable for the absorption of the septic effluent d. calculate the fixture unit load to be served 3. The recommended septic tank capacity for a fivebedroom home is _________. a. 750, b. 900, c. 1,000, d. 1,250 4. The minimum distance between a cesspool and a water supply line, as noted in Table 7, is _________. a. 100 feet b. 20 feet c. 15 feet d. not recommended as a substitute for a septic tank 5. What approximate percentage of new home construction employs a septic tank/soil absorption sewage disposal system? a. 15 percent b. 20 percent c. 25 percent d. 30 percent 6. Distribution boxes _________. a. are required by many codes b. should be used only when specifically required by code c. offer practically no advantages d. all of the above


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PSD 139


7. The absorption area to be provided for an individual residence containing three bedrooms with a percolation rate of three minutes is recommended to be _________. a. 100 square feet b. 200 square feet c. 300 square feet d. 600 square feet

8. A covered pit with an open-jointed or perforated lining into which raw sewage is discharged is called a ________. a. septic tank b. cesspool c. seepage pit d. none of the above 9. The drain lines for distributing the effluent from the septic tank should be spaced no grater than _________ apart. a. 3 feet, b. 6 feet, c. 9 feet, d. a and b 10. The quantity of sewage flow from a single-family dwelling per person is _________ gallons per day. a. 50 b. 75 c. 100 d. 125

11. The primary purpose of a septic tank is to _________. a. distribute raw sewage to the leaching field b. chemically treat raw sewage c. vent odors to atmosphere d. act as a settling tank 12. Sewage pit connecting piping _________. a. should be laid at a minimum grade of 2 percent b. must be 6 inches in diameter minimum c. must be a least 5 feet deep d. none of the above

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Plumbing Systems & Design Continuing Education Application Form This form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who ear a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required). 1. Photocopy this form or download it from www.psdmagazine.org. 2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space. 3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form. 4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656) or fax (773-695-9007). Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________ I am applying for the following continuing education credits:




Signature Expiration date: Continuing education credit will be given for this examination through May 31, 2008. Applications received after that date will not be processed.



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Private Sewage Disposal Systems (PSD 139) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

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Sanitary Drainage Systems

PSD 142



NOVEMBER 2007

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Sanitary Drainage Systems


INTRODUCTION The purpose of the sanitary drainage system is to remove effluent discharged from plumbing fixtures and other equipment to an approved point of disposal. A sanitary drainage system generally consists of horizontal branches, vertical stacks, a building drain inside the building, and a building sewer from the building wall to the point of disposal. To economically design a sanitary drainage system, use the smallest pipes according to the code that can rapidly carry away the soiled water from individual fixtures without clogging the pipes, leaving solids in the piping, generating excessive pneumatic pressures at points where the fixture drains connect to the stack (which might cause the reduction of trap water seals and force sewer gases back through inhabitable areas), and creating undue noise. Since vents and venting systems are described in Chapter 3 of this volume, the following discussion centers only on the design of drain and waste systems.

CODES AND STANDARDS Plumbing codes establish a minimum acceptable standard for the design and installation of systems, including sanitary drainage. There are various model codes, but some states and large cities have adopted plumbing codes other than the ones usually associated with the region. Because of this non-standardization, the actual plumbing code used for each specific project must be obtained from a responsible code official. There are a variety of different codes used to lay out and size interior sanitary drainage system. Some codes have been adopted by major cities such as New York, Chicago, Los Angles, and others. The information pertaining to sanitary design for any specific project appears in the approved local plumbing code and must be the primary method used for the accepted methods and sizing. The tables and charts appearing in this chapter are used only to illustrate and augment discussions of sizing methods, sizing procedures, and design methods and should not be used for actual design purposes.

FLOW IN STACKS, BUILDING DRAINS, AND FIXTURE DRAINS Flow in Stacks A stack is considered a main vertical pipe that carries away discharge from within a facility of water closets and urinals (soil stack) or other clear water waste from equipment and nonsanitary fixtures (waste stack). Flow in the drain empties into the vertical stack fitting, which may be a long-turn tee-wye or a short-turn or sanitary tee. Each of these fittings permits flow from the drain to enter the stack with a component directed vertically downward. Depending on the rate of flow out of the drain into the stack, the diameter of the stack, the type of stack fitting, and the flow down the stack from higher levels, if any, the discharge from the fixture drain may or may not fill the cross section of the stack at the level of entry. In any event, as soon as

the water enters the stack, the force of gravity rapidly accelerates it downward, and before it falls very far, it assumes the form of a sheet around the wall of the stack, leaving the center of the pipe open for the flow of air. This sheet of water continues to accelerate until the frictional force exerted by the wall of the stack on the falling sheet of water equals the force of gravity. From that point on—if the distance the water falls is great enough and provided that no flow enters the stack at lower levels to interfere with the sheet—the sheet remains unchanged in thickness and velocity until it reaches the bottom of the stack. The ultimate vertical velocity the sheet attains is called the “terminal velocity.” The distance the sheet must fall to attain this terminal velocity is called the “terminal length.” Following are the formulae developed for calculating the terminal velocity and terminal length: Equation 1

()

Q 2/5 VT = 3.0 d LT = 0.052VT2 where V T = Terminal velocity in stack, fps (m/s) LT = Terminal length below point of flow entry, ft (m) Q = Quantity rate of flow, gpm (L/s) d = Diameter of stack, in. (mm) Terminal velocity is approximately 10 to 15 fps (3.05 to 4.57 m/s), and this velocity is attained within 10 to 15 ft (3.05 to 4.57 m) of fall from the point of entry. At the center of the stack is a core of air that is dragged along with the water by friction and for which a supply source must be provided if excessive pressures in the stack are to be avoided. The usual means of supplying this air are through the stack vent or vent stack. The entrained air in the stack causes a pressure reduction inside the stack, which is caused by the frictional effect of the falling sheet of water dragging the core of air along with it. If the sheet of water falling down the stack passes a stack fitting through which the discharge from a fixture is entering the stack, the water from the branch mixes with or deflects the rapidly moving sheet of water. An excess pressure in the drain from which the water is entering the stack is required to deflect the sheet of water flowing downward or mix the branch water with it. The result is a backpressure created in the branch, which increases with the flow rate and flow velocity down the stack and with the rate of flow out of the drain. The importance of this research is that it conclusively abolishes the myth that water falling from a great height will destroy the fittings at the base of a stack. The velocity at the base of a 100-story stack is only slightly and insignificantly greater than the velocity at the base of a three-story stack. The concern is the weight of the stack, which must be supported by clamps at each floor level.

Reprinted from Plumbing Engineering Design Handbook, Volume 2: Plumbing Systems, Chapter 1: “Sanitary Drainage Systems.” © American Society of Plumbing Engineers. 2 Plumbing Systems & Design

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sure reduction is negligible; it amounts to only a small fraction Flow in Building Drains Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com When the sheet of water reaches the bend at the base of the of an inch (a millimeter) of water. What causes appreciable presstack, it turns at approximately right angles into the building sure reductions is the partial or complete blocking of the stack drain. Flow enters the horizontal drain at a relatively high veloc- by water flowing into the stack from a horizontal branch. A small increase in pneumatic pressure will occur in the ity compared to the velocity of flow in a horizontal drain under uniform flow conditions. The slope of the building drain is not building drain even if there is no complete blocking of the airadequate to maintain the velocity that existed in the vertical flow by a hydraulic jump or by submergence of the outlet and sheet when it reached the base of the stack and must flow hori- the building sewer. This is due to the decrease in cross-sectional zontally. The velocity of the water flowing along the building area available for airflow when the water flowing in the drain drain and sewer decreases slowly then increases suddenly as has adapted itself to the slope and diameter of the drain. the depth of flow increases and completely fills the cross section FIXTURE DISCHARGE CHARACTERISTICS of the drain. This phenomenon is called a “hydraulic jump.” The discharge characteristic curves—flow rates as a function of The critical distance at which the hydraulic jump may occur time—for most water closet bowls have the same general shape, varies from immediately at the stack fitting to 10 times the diambut some show a much lower peak and a longer period of diseter of the stack downstream. Less hydraulic jump occurs if the charge. The discharge characteristics for various types of water horizontal drain is larger than the stack. After the hydraulic closet bowls, particularly low-flow water closets, have a sigjump occurs and water fills the drain, the pipe tends to flow full nificant impact on estimating the capacity of a sanitary drainuntil the friction resistance of the pipe retards the flow to that of age system. Other plumbing fixtures, such as sinks, lavatories, uniform flow conditions. and bathtubs, may produce similar surging flows in drainage systems, but they do not have as marked of an effect as water Flow in Fixture Drains Determination of the required drain size is a relatively simple closets. Drainage Loads Single-family dwellings contain certain matter, since the fixture drain must be adequate only to carry the discharge from the fixture to which it is attached. Because of plumbing fixtures—one or more bathroom groups, each consistthe problem of self-siphonage, however, it is advisable to select ing of a water closet, a lavatory, and a bathtub or shower stall; a the diameter of the drain so that the drain flows little more than kitchen sink, dishwasher, and washing machine; and, possibly, half full under the maximum discharge conditions likely to be a set of laundry trays. Large buildings also have other fixtures, such as slop sinks and drinking water coolers. The important imposed by the fixture. For example, a lavatory drain capable of carrying the flow dis- characteristic of these fixtures is that they are not used continucharged from a lavatory may still flow full over part or all of its ously. Rather, they are used with irregular frequencies that vary length. There are several reasons for this. The vertical compo- greatly during the day. In addition, the various fixtures have nent of the flow out of the trap into the drain tends to make the quite different discharge characteristics regarding both the averwater attach itself to the upper elements of the drain, and a slug age rate of flow per use and the duration of a single discharge. of water is formed, filling the drain at that point. If there is not Consequently, the probability of all the fixtures in the building sufficient air aspirated through the overflow, the pipe will flow operating simultaneously is small. Assigning drainage fixture full for part of its length, with the average velocity of flow being unit (dfu) values to fixtures to represent their load-producing less than the normal velocity for the rate of flow in the drain at effect on the plumbing system was originally proposed in 1923 by Dr. Roy B. Hunter. The fixture unit values were designed for a given slope. If the fixture considered is a water closet, the surge of water application in conjunction with the probability of simultaneous from the closet will continue almost without change even use of fixtures to establish the maximum permissible drainage along a very long drain until it reaches the stack. Thus, it can be loads expressed in fixture units rather than in gallons per minute assumed, for all practical purposes, that the surge caused by the (gpm, L/s) of drainage flow. Table 1 gives the recommended fixdischarge of a water closet through a fixture drain reaches the ture unit values. The plumbing engineer must conform to local stack or horizontal branch with practically the same velocity it code requirements. had when it left the fixture.

PNEUMATIC PRESSURES IN A SANITARY DRAINAGE SYSTEM Because of the pressure conditions in a stack and a building drain, the wastewater does not fill the cross section anywhere, so the air can flow freely along with the water. The water flowing down the wall of the stack drags air with it by friction and carries it through the building drain to the street sewer. The air is then vented through the main street sewer system so dangerous pressures do not build up. The generally accepted pressure is plus or minus 1 inch of water column. If air is to enter the top of the stack to replace the air being carried along with the water, there must be a pressure reduction inside the stack. Because of the head loss necessary to accelerate the air and to provide for the energy loss at the entrance, however, this pres-

Table 1 Residential Drainage Fixture Unit (dfu) Loads Fixture Drainage Fixture Units (dfu) Bathtub Clothes washer Dishwasher Floor drain Laundry tray Lavatory, single Lavatory, in sets of 2 or 3 Shower (each head) Sink (including dishwasher and garbage disposer) Water closet (1.6-gpf gravity tank) Water closet (1.6-gpf flushometer tank) Water closet (1.6-gpf flushometer valve) NOVEMBER 2007

IPC 2 3 2 3 2 1 2 2 3 4 5 4

UPC 3 3 2 * 2 1 2 2 3 4 5 4

* Trap loadings 1¼" 1 dfu 1½" 3 dfu 2“ 4 dfu 3" 6 dfu 4" 8 dfu


CONTINUING EDUCATION: Sanitary Drainage Systems A dfu is a quantity of load-producing discharge in relation to tures. For example, the 500 fu is the maximum loading for a 4-in. Simpo PDF Merge and Split Unregistered Version(100-mm) - http://www.simpopdf.com that of a lavatory. stack, thus 147 gpm (9.3 L/s) is equivalent to 500 fu. Dr. Hunter conceived the idea of assigning a fixture unit value This is the total load from all branches. to represent the degree to which a fixture loads a system when It should be noted that there is a restriction of the amount used at the maximum assumed flow and frequency. The pur- of flow permitted to enter a stack from any branch when the pose of the fixture unit concept is to make it possible to calcu- stack is more than three branch intervals. If an attempt is made late the design load of the system directly when the system is a to introduce too large a flow into the stack at any one level, the combination of different kinds of fixtures, each having a unique inflow will fill the stack at that level and will even back up the loading characteristic. Current or recently conducted studies of water above the elevation of inflow, which will cause violent drainage loads on drainage systems may change these values. pressure fluctuations in the stack—resulting in the siphoning of These include studies of (1) reduced flow from water-saving fix- trap seals—and may also cause sluggish flow in the horizontal tures; (2) models of stack, branch, and house drain flows; and branch. This problem was solved in a study of stack capacities (3) actual fixture use. made by Wyly and Eaton at the National Bureau of Standards for the Housing and Home Finance Agency in 1950. STACK CAPACITIES The water flowing out of the branch can enter the stack only by The criterion of flow capacities in drainage stacks is based on mixing with the stream flowing down the stack or by deflecting the limitation of the water-occupied cross section to a speciit. Such a deflection of the high-velocity stream coming down fied fraction (rs) of the cross section of the stack where terminal the stack can be accomplished only if there is a large enough velocity exists, as suggested by earlier investigations. hydrostatic pressure in the branch, since a force of some kind is Flow capacity can be expressed in terms of the stack diameter required to deflect the downward flowing stream and therefore and the water cross section: change its momentum. This hydrostatic pressure is built up by Equation 2 the backing up of the water in the branch until the head thus Q = 27.8 × rs5/3 × D8/3 created suffices to change the momentum of the stream already in the stack to allow the flow from the branch to enter the stack. where The magnitude of the maximum hydrostatic pressure that Q = Capacity, gpm (L/s) should be permitted in the branch as a result of the backing up rs = Ratio of cross-sectional area of the sheet of water to of the spent water is based on the consideration that this backup cross-sectional area of the stack should not be sufficiently great to cause the water to back up D = Diameter of the stack, in. (mm) into a shower stall or to cause sluggish flow. It is half the diamValues of flow rates based on r = ¼, 7⁄24, and 1⁄3 are tabulated in eter of the horizontal branch at its connection to the stack. That Table 2. is, it is the head measured at the axis of the pipe that will cause the branch to flow full near the exit. Table 2 Capacities of Stacks When a long-turn tee-wye is used to connect the branch to Flow, gpm (L/s) Pipe Size, the stack, the water has a greater vertical velocity when it enters in. (mm) r = 1⁄4 r = 7⁄24 r = 1⁄3 2 (50) 17.5 (1.1) 23.0 (1.45) 28 (1.77) the stack than it does when a sanitary tee is used, and the back 3 (80) 52 (3.28) 70 (4.41) 85 (5.36) pressures should be smaller in this case for the same flows down 4 (100) 112 (7.07) 145 (9.14) 180 (11.35) the stack and in the branch. 5 (125) 205 (12.93) 261 (16.5) 324 (20.44) Table 3 shows the maximum permissible fu loads for sanitary 6 (150) 330 (20.82) 424 (26.8) 530 (33.43) stacks. The procedure for sizing a multistory stack (greater than 8 (200) 710 (44.8) 913 (57.6) 1,140 (72) three floors) is to first size the horizontal branches connected to 10 (250) 1,300 (82.0) 1,655 (104.4) 2,068 (130.5) the stack. This is done by totaling the fixture units connected to 12 (300) 2,082 (131.4) 2,692 (170) 3,365 (212.3) Whether or not Equation 2 can be used safely to predict stack capacities remains to be confirmed and accepted. However, it provides a definite law of variation of stack capacity with diameter. If this law can be shown to hold for the lower part of the range of stack diameters, it should be valid for the larger diameters. It should be remembered that both F.M. Dawson and Dr. Hunter, in entirely independent investigations, came to the conclusion that slugs of water, with their accompanying violent pressure fluctuations, did not occur until the stack flowed ¼ to 1 ⁄3 full. Most model codes have based their stack loading tables on a value of r = ¼ or 7⁄24. The recommended maximum permissible flow in a stack is 7⁄24 of the total cross-sectional area of the stack. By substituting r = 7⁄24 into Equation 2, the corresponding maximum permissible flow for the various sizes of pipe in gpm (L/s) can be determined. Table 1‑3 lists the maximum permissible fixture units (fu) to be conveyed by stacks of various sizes. The table was created by taking into account the probability of simultaneous use of fix4 Plumbing Systems & Design

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Table 3 Horizontal Fixture Branches and Stacks Maximum Number of Drainage Fixture Units (dfu) that May Be Connected

Diameter of pipe, in. (mm)

1½ 2 2½ 3 4 5 6 8 10 12 15

(40) (50) (65) (80) (100) (125) (150) (200) (250) (300) (380)

Any Horizontal Fixture Brancha

3 6 12 20b 160 360 620 1,400 2,500 3,900 7,000

1 Stack of 3 or Fewer Branch Intervals

4 10 20 48b 240 540 960 2,200 3,800 6,000

Stacks with More than 3 Branch Intervals Total at Total for 1 Branch Stack Interval

8 24 42 72b 500 1,100 1,900 3,600 5,600 8,400

2 6 9 20b 90 200 350 600 1,000 1,500

a Does not include branches of the building drain. b No more than two water closets or bathroom groups within each branch interval or more than six water closets or bathroom groups on the stack.

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each branch and size in accordance with Figure 1 Procedure for Sizing an Offset Stack Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com column 2 in Table 3. Next, total all the fixture units connected to the stack and determine the size from the same table, under column 4. Immediately check the next column, “Total at One Branch Interval,” and determine if this maximum is exceeded by any of the branches. If it is exceeded, the size of the stack as originally determined must be increased at least one size, or the loading of the branches must be redesigned so maximum conditions are satisfied. Take, for example, a 4-in. (100-mm) stack more than three stories in height. The maximum loading for a 4-in. (100-mm) branch is 160 fu, as shown in column 2 of Table 3. This load is limited by column 5 of the same table, which permits only 90 fu to be introduced into a 4-in. (100-mm) stack in any onebranch interval. The stack would have to be increased in size to accommodate any branch load exceeding 90 fu. To illustrate clearly the requirements of a stack with an offset of more than 45° from the vertical, Figure 1 shows the sizing of a stack in a 12-story building where there is one offset between the fifth and sixth floors and another offset below the street floor. Sizing is computed as follows: Step 1. Compute the fixture units connected to the stack. In this case, assume 1,200 fixture units are connected to the stack from the street floor through the top floor. Step 2. Size the portion of the stack above the fifth-floor offset. There are 400 fixture units from the top floor down through the sixth floor. According to Table 3, column 4, 400 fixture units require a 4-in. (100-mm) stack. Step 3. Size the offset on the fifth floor. An offset is sized and sloped like a building drain. Step 4. Size the lower portion of the stack from the fifth floor down through the street floor. The lower portion of the stack must be large enough to serve all fixture units connected to it, from the top floor down (in this case 1,200 fixture units). According to Table 3, 1,200 fixture units require a 6-in. (150-mm) stack. Step 5. Size and slope the offset below the street floor the same as a building drain. The fixture on the sixth floor should be connected to the stack at least 2 ft (0.6 m) above the offset. If this is not possible, then connect them separately to the stack at least 2 ft (0.6 m) below the offset. If this is not possible either, run the fixture drain down to the fifth or fourth floor and connect to the stack at that point.

CAPACITIES OF SLOPING DRAINS The characteristics of sewage are the same as plain water. Capacities of horizontal or sloping drains are complicated by surging flow. The determination of drain size is based on highly fluctuating or surging flow conditions in the horizontal branches carrying the discharge of fixtures to the soil or waste stack. After falling down the vertical stack, the water is assumed to enter the building drain with peaks of the surges leveled off somewhat but still in a surging condition. In a large building covering considerable ground area there are probably several primary branches and certainly at least one secondary branch. After the water enters the building drain, the surge continues to level off, becoming more and more nearly uniform, particularly after the hydraulic jump has occurred. If the secondary branch is long enough, and if the drain serves a large number of fixtures, the flow may become substantially uniform before it reaches the street sewer. NOVEMBER 2007


CONTINUING EDUCATION: Sanitary Drainage Systems Equation 5b Steady, Uniform Flow Conditions in Sloping Drains Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Although the equations of steady, uniform flow in sloping drains Q = A × 1.486 × R2/3 × S1/2 n should not be used to determine the capacities of sloping drains This is the formula used by many plumbing engineers to deal in which surging flow exists, flow computations based on these formulas afford a rough check on values obtained by the more with sloping drain problems. The significant hydraulic paramcomplicated methods that are applicable to surging flow. Hence, eters used in the above equation are listed in Table 4. It should be noted that the units in the above equations should three of the commonly used formulas for flow in pipes will be considered: (1) Hazen and Williams, (2) Darcy-Weisbach, and be converted to the proper units whenever utilizing Equations 5a or 5b. (3) Manning. Hazen and Williams formula This formula is Table 4 Values of R, R2/3, AF, and AH usually written as follows: AF (Cross-Sectional AH (Cross-Sectional Equation 3 Pipe Size, Area for2 Full2 Flow), Area for Half-full 2/3 D 0.63 0.54 in. (mm) R = ⁄4, ft (mm) R , ft (mm) ft (m ) Flow), ft2 (m2) V = 1.318 × C × R × S 1½ (40) 0.0335 (1.02) 0.1040 (3.17) 0.01412 (0.0013) 0.00706 (0.00065) where 2 (50) 0.0417 (1.27) 0.1200 (3.66) 0.02180 (0.0020) 0.01090 (0.0009) V = Mean velocity of flow, fps (m/s) 2½ (65) 0.0521 (1.59) 0.1396 (4.24) 0.03408 (0.0031) 0.01704 (0.0015) C = Hazen and Williams coefficient 3 (80) 0.0625 (1.90) 0.1570 (4.78) 0.04910 (0.0046) 0.02455 (0.0023) R = Hydraulic radius of pipe, ft (m) 4 (100) 0.0833 (2.54) 0.1910 (5.82) 0.08730 (0.0081) 0.04365 (0.0040) S = Slope of pressure gradient 5 (125) 0.1040 (3.17) 0.2210 (6.74) 0.13640 (0.0127) 0.06820 (0.0063) 6 (150) 0.1250 (3.81) 0.2500 (7.62) 0.19640 (0.0182) 0.09820 (0.0091) The exponents of R and S in Equation 3 have been 8 (200) 0.1670 (5.09) 0.3030 (9.23) 0.34920 (0.0324) 0.17460 (0.0162) selected to make the coefficient C as nearly constant 10 (250) 0.2080 (6.33) 0.3510 (10.70) 0.54540 (0.0506) 0.27270 (0.0253) as possible for different pipe diameters and for dif12 (300) 0.2500 (7.62) 0.3970 (12.10) 0.78540 (0.0730) 0.39270 (0.0364) ferent velocities of flow. Thus, C is approximately 15 (380) 0.3125 (9.53) 0.4610 (14.05) 1.22700 (0.0379) 0.61350 (0.0570) constant for a given pipe roughness. Darcy-Weisbach formula In this formula the dimensionless Slope of Horizontal Drainage Piping friction coefficient f varies with the diameter of the pipe, the Horizontal drains are designated to flow at half-full capacity velocity of flow, the kinematic viscosity of the fluid flowing, and under uniform flow conditions to minimize the generation of the roughness of the walls. It is usually written as follows: pneumatic pressure fluctuations. A minimum slope of ¼ in./ ft (6.4 mm/m) should be provided for pipe 3 in. (80 mm) and Equation 4 2 smaller, 1⁄8 in./ft (3.2 mm/m) for 4-6-in. (100-150-mm) pipe, f L V hf = D 2g and 1⁄16 in./ft (1.6 mm/m) for pipe 8 in. (200 mm) and larger. where These slopes are not a hard and fast rule and might be less hf = Pressure drop or friction loss, ft (m) under unusual conditions. The signer must confirm required f = Friction coefficient slopes with the local code authority. These minimum slopes L = Length of pipe, ft (m) are required to maintain a velocity of flow greater than 2 fps D = Diameter of pipe, ft (m) for scouring action. Table 5 gives the approximate velocities for V = Mean velocity of flow, fps (m/s) given flow, slopes, and diameters of horizontal drains based on g = Acceleration of gravity, 32.2 fps2 (9.8 m/s2) the Manning formula for half-full pipe and n = 0.015. A flow velocity of 2 fps will prevent the solids within a pipe Manning formula The Manning formula, which is similar to the Hazen and Williams formula, is meant for open-channel from settling out and forming a system stoppage. Table 6 has been prepared to give the size of a pipe in conjunction with flow flow and is usually written as follows: rate to maintain a self-cleansing velocity of 2 fps. Equation 5 Load or Drainage Piping 0.67 0.50 V = 1.486 × R2/3 × S1/2 = 1.486 n n × R × S The recommended loads for building drains and sewers are tabIn this formula, n is the Manning coefficient and varies with ulated in Table 7. This table shows the maximum number of fixture units that may be connected to any portion of the building the roughness of the pipe and the pipe diameter. The quantity of flow is equal to the cross-sectional area of flow drain or building sewer for given slopes and diameters of pipes. times the velocity of flow obtained from the above three equa- For example, an offset below the lowest branch with 1,300 fu at ¼ in./ft (6.4 mm/m) slope requires an 8-in. (200-mm) pipe. tions. This can be expressed as: For devices that provide continuous or semi-continuous flow Equation 5a into the drainage system, such as sump pumps, ejectors, and airQ = AV conditioning equipment, a value of 2 fu can be assigned for each gpm (L/s) of flow. For example, a sump pump with a discharge where rate of 200 gpm (12.6 L/s) is equivalent to 200 × 2 = 400 fu. Q = Quantity rate of flow, cfs (m3/s) A = Cross-sectional area of flow, ft2 (m2) COMPONENTS OF SANITARY DRAINAGE SYSTEMS V = Velocity of flow, fps (m/s) By substituting the value of V from Manning’s formula, the Sumps and Ejectors quantity of flow in variously sized drains of the same material The distinction between sump and ejector pumps is more terminology than actual fact. A sump pump is designed to transport can be calculated as clear, non-sanitary wastewater with some turbidity and sus-

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Table 5 Approximate Discharge Rates and Velocities in Sloping Drains, n = 0.015a Actual Inside Half-full Flow Discharge Rate and Velocity Actual Inside 1 1 1 1 ⁄16 in./ft (1.6 mm/m) Slope ⁄8 in./ft (3.2 mm/m) Slope ⁄4 in./ft (6.4 mm/m) Slope ⁄2 in./ft (12.7 mm/m) Slope Diameter of Pipe, Disch., Velocity, fps Disch., Velocity, fps Disch., Velocity, fps Disch., Velocity, fps in. (mm) gpm (L/s) (mm/s) gpm (L/s) (mm/s) gpm (L/s) (mm/s) gpm (L/s) (mm/s) 1¼ (31.8) 3.40 (0.21) 1.78 (45.5) 13⁄8 (34.9) 3.13 (0.20) 1.34 (0.41) 4.44 (0.28) 1.90 (48.3) 1½ (38.9) 3.91 (0.247) 1.42 (0.43) 5.53 (0.35) 2.01 (51.1) 15⁄8 (41.28) 4.81 (0.30) 1.50 (0.46) 6.80 (0.38) 2.12 (53.9) 2 (50.8) 8.42 (0.53) 1.72 (0.52) 11.9 (0.75) 2.43 (61.8) 2½ (63.5) 10.8 (0.68) 1.41 (0.43) 15.3 (0.97) 1.99 (0.61) 21.6 (1.36) 2.82 (71.7) 3 (76.3) 17.6 (1.11) 1.59 (0.49) 24.8 (1.56) 2.25 (0.69) 35.1 (2.21) 3.19 (81.1) 4 (101.6) 26.70 (1.68) 1.36 (34.6) 37.8 (2.38) 1.93 (0.59) 53.4 (3.37) 2.73 (0.83) 75.5 (4.76) 3.86 (98.2) 5 (127) 48.3 (3.05) 1.58 (40.2) 68.3 (4.30) 2.23 (0.68) 96.6 (6.10) 3.16 (0.96) 137 (8.64) 4.47 (113.7) 6 (152.4) 78.5 (4.83) 1.78 (45.3) 111 (7.00) 2.52 (0.77) 157 (10) 3.57 (1.09) 222 (14.0) 5.04 (128.2) 8 (203.2) 170 (10.73) 2.17 (55.2) 240 (15.14) 3.07 (0.94) 340 (21.5) 4.34 (1.32) 480 (30.3) 6.13 (155.9) 10 (256) 308 (19.43) 2.52 (64.1) 436 (27.50) 3.56 (1.09) 616 (38.9) 5.04 (1.54) 872 (55.0) 7.12 (181.0) 12 (304.8) 500 (31.55) 2.83 (72.0) 707 (44.60) 4.01 (1.22) 999 (63.0) 5.67 (1.73) 1413 (89.15) 8.02 (204.0)


n = Manning coefficient, which varies with the roughness of the pipe. For full flow: Multiply discharge by 2.00. For full flow: Multiply velocity by 1.00. For smoother pipe: Multiply discharge and velocity by 0.015 and divide by n of another pipe. a

Table 6 Slopes Of Cast Iron Soil Pipe Sanitary Sewers Required To Obtain Self-cleansing Velocities Of 2.0 And 2.5 Ft./sec. (Rased On Mannings Formula With N = .012) 1/4 Full 1/2 Full 3/4 Full Full Pipe Velocity Slope Flow Slope Flow Slope Flow Slope Flow Size (in.) (ft./sec.) (ft./ft.) (Gal./min.) (ft./ft.) (Gal./min.) (ft./ft.) (Gal./min.) (ft./ft.) (Gal./min.) 2.0 2.0 0.0313 4.67 0.0186 9.34 0.0148 14.09 0.0186 18.76 2.5 0.0489 5.04 0.0291 11.67 0.0231 17.62 0.0291 23.45 3.0 2.0 0.0178 10.71 0.0107 21.46 0.0085 32.23 0,0107 42.91 2.5 0.0278 13.47 0.0167 26.62 0.0133 40.29 0.0167 53.64 4.0 2.0 0.0122 19.03 0.0073 38.06 0.0058 57.01 0.0073 76.04 2.5 0.0191 23.79 0.0114 47.58 0.0091 71.26 0.0114 95.05 5.0 2.0 0.0090 29.89 0.0054 59.79 0.0043 89.59 0.0054 119.49 2.5 0.0141 37.37 0.0085 74.74 0.0067 111.99 0.0085 149.36 6.0 2.0 0.0071 43.18 0.0042 86.36 0.0034 129.54 0.0042 172.72 2.5 0.0111 53.98 0.0066 101.95 0.0053 161.93 0.0066 215.90 8.0 2.0 0.0048 77.20 0.0029 154.32 0.0023 231.52 0.0029 308.64 2.5 0.0075 96.50 0.0045 192.90 0.0036 289.40 0.0045 385.79 10.0 2.0 0.0036 120.92 0.0021 241.85 0.0017 362.77 0.0021 483.69 2.5 0.0056 151.15 0.0033 302.31 0.0026 453.46 0.0033 604.61 12.0 2.0 0.0028 174.52 0.0017 349.03 0.0013 523.55 0.0017 678.07 2.5 0.0044 218.15 0.0026 436.29 0.0021 654.44 0.0026 612.58 15.0 2.0 0.0021 275.42 0.0012 550.84 0.0010 826.26 0.0012 1101.68 2.5 0.0032 344.28 0.0019 688.55 0.0015 1032.83 0.0019 1377.10 pended solids no larger than sand grains. An ejector pump is designed to transport sanitary waste and larger solids suspended in the effluent. All effluent is a liquid with solids suspended in it but has the same hydraulic characteristics as water. Building drains that cannot flow directly into a sewer by gravity must be discharged into a covered basin from which fluid is lifted into the building’s gravity drainage system by automatic pump equipment or by any equally efficient method approved by the administrative authority. An ejector basin must be of airtight construction and must be vented. It is airtight to prevent the escape of foul odors generated by sanitary waste from the subdrainage system. Since it is airtight, a vent is required to relieve the air in the basin as wastes discharge into it and also to supply air to the basin while the contents are being discharged to the sanitary gravity drainage system. A duplex pump system shall be used. If one pump breaks down, the control system will alert the second pump to start. The system will remain in operation and no damage will be caused by the cessation of system operation. When a

Table 7 Building Drains and Sewersa Maximum Permissible Fixture Units for Sanitary Building Drains and Runouts From Stacks Diameter Slope, in./ft (mm/m) of Pipe, in. (mm) 1⁄16 (1.6) 1⁄8 (3.2) 1⁄4 (6.4) 1⁄2 (12.7) 2 (50) 21 26 2½ (65) 24 31 3 (80) 20 42b 50b 4 (100) 180 216 250 5 (125) 390 480 575 6 (150) 700 840 1,000 8 (200) 1400 1600 1,920 2,300 10 (250) 2500 2900 3,500 4,200 12 (300) 2900 4600 5,600 6,700 15 (380) 7000 8300 10,000 12,000 On-site sewers that serve more than one building may be sized according to the current standards and specifications of the administrative authority for public sewers. b No more than two water closets or two bathroom groups, except in single-family dwellings, where no more than three water closets or three bathroom groups may be installed. Check the local codes in the area served for exact requirements or restrictions. a

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CONTINUING EDUCATION: Sanitary Drainage Systems duplex unit is used, each pump should be sized for 100 percent 2. At every change of direction greater than 45°. Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com flow, and it is good practice to have the operation of the pumps 3. A maximum distance between cleanouts of 50 ft (15.1 m) alternate automatically. should be maintained for piping 4 in. (100 mm) and smaller, A sump basin need not be airtight or vented because of the and of 75 ft (22.9 m) for larger piping. Underground sanitary lack of objectionable odors. Incoming water is collected in the sewer piping larger than 10 in. (250 mm) in diameter should sump before it is pumped to the gravity drain pipe. Heavybe provided with cleanouts at every change of direction and flow drains require large sumps to retain greater-than-usual every 150 ft (45.7 m). amounts of water, thereby creating more head pressure on the pipe inlet. Most manufacturers make their basins with bottom, 4. At the base of all stacks. side, or angle inlets and with inside caulk, no-hub, push-on, 5. To comply with applicable codes. Optional locations include: spigot, or screwed connections. Outlet connections are made to accept pressure-type pipe joints. No-hub pipe and fittings are 1. At the roof stack terminal. not acceptable on pumped discharge piping due to the pressure 2. At the end of horizontal fixture branches or waste lines. limitations of the pipe joints. Sump and ejector systems normally use a wet pit and will have 3. At fixture traps. (Fixture traps can be pre-manufactured with cleanout plugs, although some codes prohibit the installathe pumps either above slab or submerged. They are controlled tion of this kind of trap.) with a float switch or electronic, with control switches mounted inside the basin. Typical ejector installations are illustrated in Figure 2. Typical ejector installations are illustrated in Figure 3. Cleanouts The cleanout provides access to horizontal and vertical lines to facilitate inspection and provide a means of removing obstructions such as solid objects, greasy wastes, and hair. Cleanouts, in general, must be gas- and water-tight, provide quick and easy plug removal, allow ample space for the operation of cleaning tools, have a means of adjustment to finished surfaces, be attractive in appearance, and be designed to support whatever traffic is directed over them. Some cleanouts are designed with a neoprene seal plug, which prevents “freezing” or binding to the ferrule. All plugs are machined with a straight or running thread and a flared shoulder for the neoprene gasket, permitting quick and certain removal when necessary. A maximum opening is provided for tool access. Recessed covers are available to accommodate carpet, tile, terrazzo, and other surfaces finishes and are adjustable to the exact floor level established by the adjustable housing or by the set screws. Waste lines are normally laid beneath the floor slabs at a distance sufficient to provide adequate backfill over the joints. Cleanouts are then brought up to floor-level grade by pipe extension pieces. Where the sewer line is at some distance below grade and not easily accessible through extensions, small pits or manholes with access covers must be installed. When cleanouts are installed in traffic areas, the traffic load must be considered when the materials of construction are selected. The size of the cleanout within a building should be the same size as the piping, up to 4 in. (100 mm). For larger size interior piping, 4-in. (100-mm) cleanouts are adequate for their intended purpose; however, 6-in. (150-mm) cleanouts are recommended to allow for a larger variety of access needs such as for sewer video equipment. Cleanouts should be provided at the following locations:

Figure 2 Typical Ejector Pump Installation

1. Five ft 0 in. (1.5 m) outside or inside the building at the point of exit. 8 Plumbing Systems & Design

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intended for use primarily in locations where the flow reaches Floor Drains and Floor Sinks Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com A large-diameter drain with a deep sump connected to a large- high rates, such as malls, wash-down areas, and certain indusdiameter pipe passes more water faster than a smaller drain. trial applications. Table 8, which shows minimum ratios of open However, economics do not allow the designer arbitrarily to grate area based on pipe diameter, is offered as a guide for the select the largest available drain when a smaller, less-expen- selection of drains where the drain pipe diameter is known. The only drawback to using the open-area-pipe-diametersive unit will do a satisfactory job. High-capacity drains are ratio method is that all drain manufacturers do not list the total Table 8 Recommended Grate Open Areas for Various open areas of grates in their catalogs. This information usually Floor Drains With Outlet Pipe Sizes can be obtained upon request, however. Recommended Minimum Grate For the sizing of floor drains for most indoor applications, the Open Area for Floor Drains capacity of a drain is not extremely critical because the drain’s Transverse Area Minimum Inside Nominal Pipe of Pipe, in.2a Area, in.2 primary function is to handle minor spillage or fixture overflow. Size, in. (mm) (× 10 mm2) (× 10 mm2) The exceptions are, of course, cases where equipment discharges 1½ (40) 2.04 (1.3) 2.04 (1.3) to the drain, where automatic fire sprinklers may deluge an area 2 (50) 3.14 (2.0) 3.14 (2.0) with large amounts of water, and where flushing of the floor is 3 (80) 7.06 (4.6) 7.06 (4.6) 4 (100) 12.60 (8.1) 12.06 (8.1) required for sanitation. 5 (125) 19.60 (12.7) 19.60 (12.7) Generally located floor drains or drains installed to anticipate 6 (150) 28.30 (18.3) 28.30 (18.3) a failure may not receive sufficient water flow to keep the pro8 (200) 50.25 (32.4) 50.24 (32.4) tective water seal or plumbing trap from evaporating. If it does a Based on extra-heavy soil pipe, nominal internal diameter. evaporate, sewer gases will enter the space. Automatic or manual trap primers should be installed Figure 3 Typical Submerged Sump Pump Installation to maintain a proper trap seal. (A small amount of vegetable oil will dramatically reduce the evaporation rate of infrequently used floor drains and floor sinks.) Figure 4 shows the basic components of a floor drain. Grates / Strainers The selection of grates is based on use and the amount of flow. Light-traffic areas may have a nickelbronze-finished grate, while mechanical areas may have a large, heavy-duty, ductile iron grate. The wearing of spike-heeled shoes prompted the replacement of grates with a heel-proof, ¼-in.-square (6.4-mm) grate design in public toilet rooms, corridors, passageways, promenade decks, patios, stores, theaters, and markets. Though this type of grating has less drainage capacity than the previous one, its safety feature makes it well worth the change. Grates or strainers should be secured with stainless-steel screws in nickel-bronze tops. Vandal-proof fasteners are available from most manufacturers. Vandal-proofing floor drain grates is advisable. If there is public access to the roof, consideration must be given to protecting the vent openings from vandals. In school gymnasium shower rooms, where the blocking of flat-top shower drains with paper towels can cause flooding, dome grates in the corners of the room or angle grates against the walls can be specified in addition to the regular shower drains. Shower-room gutters and curbs have become undesirable because of code requirements and the obvious dangers involved. Therefore, the passageways from shower areas into locker areas need extendedlength drains to prevent runoff water from entering the locker areas. Where grates are not secured and are subject to vehicular traffic, it is recommended that non-tilting and /or tractor-type grates be installed. When a grate NOVEMBER 2007


CONTINUING EDUCATION: Sanitary Drainage Systems Figure 4 Basic Floor-Drain Components:


(A) Removable Grate; (B) Rust-Resistant Bolts; (C) Integral, One-Piece, Flashing Ring; (D) Cast Drain Body with Sump; (E) Sediment Bucket (optional). starts to follow a wheel or is hit on one edge and starts to tilt, the skirt catches the side of the drain body and the grate slides back into its original position. Ramp-drain gratings should be slightly convex because rapidly flowing ramp water has a tendency to flow across the grate. A better solution to this problem is to place flat-top grates on a level surface at the bottom of the ramp, rather than on the ramp slope. A technique in casting grates is the reversal of pattern draft, which removes the razor-sharp edges created when grates are buffed. See Figure 5. The prevalent buffing technique is called scuff-buff because it gives the grate a slightly used appearance. The use of slots in grates is becoming obsolete because of the slicing edges they create, which cause excess wear and tear on the wheels of hand-trucks and other vehicles. Square openings are more desirable because they shorten this edge and provide greater drainage capacity than round holes. Flashing Ring This component makes an effective seal, which prevents water from passing around the drain to the area below.

Figure 5 Pattern Draft for Floor Gratings

Sediment Bucket A sediment bucket is an additional internal strainer designed to collect debris that gets by the regular strainer. It is required wherever the drain can receive solids, trash, or grit that could plug piping, such as the following locations: 1. Toilet rooms in commercial buildings should be equipped with floor drains with sediment buckets to facilitate cleaning. 2. Floor drains with sediment buckets must be provided in mechanical equipment rooms, where pumps, boilers, water chillers, heat exchangers, and HVAC equipment regularly discharge and /or must be periodically drained for maintenance and repairs. HVAC equipment requires the drainage of condensate from cooling coils using indirect drains. 3. Boilers require drains with sediment buckets. Strategically located floor drains are also required in buildings with wet fire-protection sprinkler systems to drain water in case sprinkler heads are activated. The maximum temperature of liquids discharged should be 140°F (60°C). Floor drains shall connect to a trap so constructed that it can be readily cleaned and sized to serve efficiently the purpose for which it is intended. A deep-seal-type trap or an approved automatic priming device should be provided. The trap shall be accessible either from the floor-drain inlet or by a separate cleanout within the drain. Figure 6 illustrates several types of drains that meet these conditions. Figure 6 Types of Floor Drain

(a)

(b) (a) Sharp Edge, (b) Reverse Pattern 10 Plumbing Systems & Design

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(A) Typical Drain with Integral Trap that May Be Cleaned Through Removable Strainer at Floor Level; (B) Floor Drain with Combination Cleanout and Backwater Valve, for Use Where Possibility of Backflow Exists; (C) Drain with Combined Cleanout, Backwater Valve, and Sediment Bucket. PSDMAGAZINE.ORG

discharged through a tailpiece and are typically protected from Accessories Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com A variety of accessories are available to make the basic drain back-siphonage by the vacuum breaker mounted at the tailpiece adaptable to various types of structures. The designer must entrance. Fixture wastewater type. These devices are mounted on the know the construction of the building, particularly the floor and trap of frequently used fixtures. A tapping at the overflow line deck structures, to specify the appropriate drain. will allow small amounts of wastewater to enter an adjacent, Backwater Valves infrequently used drain as the trap surges during use. A backwater valve can be installed on a building sewer/house Automatic trap primers can be obtained as pre-engineered drain when the drain is lower than the sewer line, when unusual devices, which have widely accepted approval. All direct consewer surcharges may occur due to combined storm water and nections between the sewer system and the potable water sanitary sewer systems, or when old municipal sewers incur high system must be protected from potential contamination. The rates of infiltration. A backwater valve reacts similarly to a check above-referenced primers can be manufactured, or fitted with, valve. The device consists of a mechanical flapper or disc, which devices that are approved to prevent cross-contamination. requires a certain amount of maintenance; therefore, attention must be given during the placement of these devices to a free Supports area and access for maintenance. Sediment can accumulate The location of pipe supports is usually specified by code. They on the flapper valve seat, preventing the flapper from closing are located to maintain a slope that is as uniform as possible tightly. Also, many valves employ a spring or mechanical device and will not change with time. In this regard, the rigidity of pipe to exert a positive pressure on the flapper device, which requires and joints and the possibility of creep and bedding settlement occasional lubrication. Most manufacturers of backwater valves are primary considerations. When building settlement may be provide an access cover plate for maintenance, which may also significant, special hanging arrangements may be necessary. Underground piping should be continuously and firmly supbe used as a building sewer cleanout. Figure 7 illustrates various types of backwater valves that may ported, but blocking below metal pipe is usually acceptable. Consult the manufacturer for recommendations for piping be installed where there is a possibility of backflow. materials not covered in the code and for special problems. Figure 7 Various Types of Backwater Valve Hangers should be designed adequately. To protect from damage by building occupants, allow at least a 250-lb (113.4-kg) safety factor when designing hangers. See Data Book, Volume 4, Chapter 6 for further information. Seismic restraint must also be considered. Figure 8 Combination Floor Drain and Indirect Waste Receptor

Oil Interceptors In commercial establishments such as service stations, garages, auto repair shops, dry cleaners, laundries, industrial plants, and process industries having machine shops, metal-treating process rooms, chemical process or mixing rooms, etc., there is always the problem of flammable or volatile liquids entering the drainage system, which can contaminate the sewer line and cause a serious fire or explosive condition. Oil interceptors are designed to separate and collect oils and other light-density, volatile liquids, which would otherwise be discharged into the drainage system. An oil interceptor is required wherever lubricating oil, cutting oil, kerosene, gasoline, diesel fuel, aircraft fuel, naphtha, paraffin, trisodium phosphate, or other light-density and volatile liquids are present in or around the drainage system. The interceptor is furnished with a sediment bucket, which collects debris, small parts, chips, particles, and other sediment that are frequently present in industrial waste from these types of facilities and could clog the drainage system. A gasketed, removable cover permits access for cleaning the interceptor. To eliminate pressure buildup inside the interceptor, a connection on each side of the body allows venting of the interceptor. Oil interceptors are sized in accordance with the maximum anticipated gpm (L/s) flow rate of wastewater that could be

MATERIALS Piping Materials recommended for soil and waste piping, installed aboveground within buildings, are copper alloy, copper, cast iron (hub-and-spigot or hubless), galvanized steel, or PVC plastic pipe. Underground building drains should be cast-iron soil pipe, hard-temper copper tube, ABS or PVC, PVDF, DWV pattern Schedule 40 plastic pipe with compression joints or couplings, NOVEMBER 2007


CONTINUING EDUCATION: Sanitary Drainage Systems installed with a minimum cover of 12 in. (300 mm). Corrosive Simpo PDF Merge and Split Unregistered Version wastes require suitably acid-resistant materials such as highsilicon cast iron, borosilicate glass, polypropylene, etc. (Note: Some blood analyzers discharge sodium azide, which forms a very dangerous, explosive compound with copper pipes. Either other piping must be used or the sodium azide must be kept out of the system.) The materials used for pipe fittings must be compatible with the materials utilized for piping. Fittings should slope in the direction of flow and have smooth interior surfaces without ledges, shoulders, or reductions that may obstruct the flow in piping. Drains specified with cast-iron or PVC bodies should be suitable for most installations. Where extra corrosion resistance is 3. required, high-silica cast iron, polypropylene, borosilicate glass, stainless steel, galvanized iron, or other acid-resisting material should be selected. Where a sediment bucket is used, it should be bronze or galvanized or stainless steel. Enameled sediment buckets are impractical because they chip when cleaned. In the selection of materials for top surfaces, such as grates, 4. where floor drains are visible in finished areas, appearance is a prime consideration. As cast iron will rust and galvanizing and chrome plating will eventually be worn off by traffic, the preferred material is solid, cast nickel-bronze, which maintains its attractive appearance. In a swimming pool, however, chlorine necessitates the use of chlorine-resistant materials. For large grates that will be subject to hand-truck or forklift traffic, a ductile iron grate with or without a nickel-bronze veneer is recommended. Polished brass or bronze for floor service has the disadvantage of discoloring unless there is constant traffic over it. Cast aluminum has also been found inadequate for certain floorservice applications due to excessive oxidation and its inability to withstand abrasion.

Figure 10 Spigot-Outlet Drain Body

http://www.simpopdf.com

hub or bell of the downstream pipe or fitting. See Figure 1‑10. Push-seal gasketed outlet. This type utilizes a neoprene gasket similar to standard ASTM C564 neoprene gaskets approved for hub-and-spigot, cast-iron soil pipe. A ribbed neoprene gasket is applied to the accepting pipe, thus allowing the drain outlet to be pushed onto the pipe. No-hub. This type utilizes a spigot (with no bead on the end) that is stubbed into a neoprene coupling with a stainless-steel bolting band (or other type of clamping device), which, in turn, accepts a downstream piece of pipe or headless fitting. See Figure 11. Figure 11 No-Hub-Outlet Drain Body

Joining Methods Drain and cleanout outlets are manufactured in five basic types: 1. Inside caulk. In this arrangement, the pipe extends up into the drain body and oakum is packed around the pipe tightly against the inside of the outlet. Molten lead is then poured into this ring and later stamped or caulked to correct for lead shrinkage. Current installation methods use a flexible gasket for a caulking material. See Figure 9. Figure 9 Inside-Caulk Drain Body

5. IPS or threaded. This type is a tapered female thread in the drain outlet designed to accept the tapered male thread of a downstream piece of pipe or fitting. See Figure 12. Figure 12 IPS or Threaded – Outlet Drain Body

2. Spigot outlet. This type utilizes the caulking method as outlined above, except that the spigot outlet is caulked into the 12 Plumbing Systems & Design

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Noise Transmission Simpo PDF Merge and Split Unregistered Version Avoiding direct metal-to-metal connections may reduce noise transmission along pipes. Using heavier materials generally 4. reduces noise transmission through pipe walls. Isolating piping with resilient materials, such as rugs, belts, plastic, or insulation may reduce noise transmission to the building. See Table 9 for relative noise-insulation absorption v alues. Table 9 Relative Properties of Selected Plumbing Materials for Drainage Systems Noise Corrosion Materials Absorption Resistancea ABS Fair Good Cast iron Excellent Good b Clay Excellent c Concrete Faird Copper Fair Good b Glass borosilicate Excellent Polypropylene Fair Excellent PVC Fair Excellent c Silicon iron Excellent Steel, galvanized Good Fair T his refers to domestic sewage. Consult manufacturer for resistance to particular chemicals. b Since these materials are used only aboveground for chemical waste systems, this is not applicable. c This material is usually allowed only belowground. d Susceptible to corrosion from hydrogen sulfide gas. a

Building sewer installation The installation of building sewers is very critical to the operation of the sewer. Inadequate bedding in poor soils may allow the sewer to settle, causing dips and low points in the sewer. The settlement of sewers interrupts flow, diminishes minimum cleansing velocity, reduces capacity, and creates a point where solids can drop out of suspension and collect. The following are some guidelines for installing building sewers: 1. Compacted fill. Where natural soil or compacted fill exists, the trench must be excavated in alignment with the proposed pitch and grade of the sewer. Depressions need to be cut out along the trench line to accept the additional diameter at the piping joint or bell hub. A layer of sand or pea gravel is placed as a bed in the excavated trench because it is easily compacted under the pipe, allowing more accurate alignment of the pipe pitch. The pipe settles into the bed and is firmly supported over its entire length. 2. Shallow fill. Where shallow amounts of fill exist, the trench can be over-excavated to accept a bed of sand, crushed stone, or similar material that is easily compacted. Bedding should be installed in lifts (layers), with each lift compacted to ensure optimum compaction of the bedding. The bed must be compacted in alignment with the proposed pitch and grade of the sewer. It is recommended that pipe joints or bell hub depressions be hand-prepared due to the coarse crushed stone. The soil-bearing weight determines trench widths and bedding thickness. 3. Deep fill. Where deep amounts of fill exist, the engineer should consult a geotechnical engineer, who will perform soil borings to determine the depths at which soils with proper bearing capacities exist. Solutions include compact-

ing existing fill by physical means or removing existing fill

http://www.simpopdf.com and replacing it with crushed stone structural fill.

Backfilling. Backfilling of the trench is just as critical as the compaction of the trench bed and the strength of existing soils. Improper backfill placement can dislodge pipe and cause uneven sewer settlement, with physical depressions in the surface. The type of backfill material and compaction requirements need to be reviewed to coordinate with the type of permanent surface. Landscaped areas are more forgiving of improper backfill placement than hard surface areas such as concrete or bituminous paving.

Care must be taken when using mechanical means to compact soils above piping. Mechanical compaction of the first layer above the pipe by vibrating or tamping devices should be done with caution. Compacting the soil in 6-in. (150-mm) layers is recommended for a good backfill. Proper sewer bedding and trench backfill will result in an installation that can be counted upon for long, trouble-free service.

Sanitation All drains should be cleaned periodically, particularly those in markets, hospitals, food-processing areas, animal shelters, morgues, and other locations where sanitation is important. Where sanitation is important, an acid-resisting enameled interior in floor drains is widely accepted. The rough surfaces of either brass or iron castings collect and hold germs, fungusladen scum, and fine debris that usually accompany drain waste. There is no easy or satisfactory way to clean these rough surfaces. The most practical approach is to enamel them. The improved sanitation compensates for the added expense. However, pipe threads cannot be cut into enameled metals because the enameling will chip off in the area of the machining. Also, pipe threads themselves cannot be enameled; therefore, caulked joints should be specified on enameled drains. Most adjustable floor drains utilize threaded adjustments. The drains cannot be enameled because of this adjusting thread. However, there are other adjustable drains that use sliding lugs on a cast thread and may be enameled. Another point to remember is that a grate or the top ledge of a drain can be enameled, but the enamel will not tolerate traffic abrasion without showing scratches and, eventually, chipping. The solution to this problem is a stainless-steel or nickelbronze rim and grate over the enameled drain body, a common practice on indirect waste receptors, sometimes referred to as “floor sinks.” Specifiers seem to favor the square, indirect waste receptor, but the round receptor is easier to clean and has better anti-splash characteristics. For cases where the choice of square or round is influenced by the floor pattern, round sinks with square tops are available. In applications such as hospital morgues, cystoscopic rooms, autopsy laboratories, slaughterhouses, and animal dens, the enameled drain is fitted with a flushing rim. This is most advisable where blood or other objectionable materials might cling to the sidewalls of the drain. Where the waste being drained can create a stoppage in the trap, a heel inlet on the trap with a flushing connection is recommended in addition to the flushing rim, which merely keeps the drain sides clean. (This option may not be allowed by certain codes.) A 2-in. (50-mm) trap flushes more effectively than a 3-in. (80-mm) trap because it allows the flushing stream to drill through the debris rather than completely flush it out. A NOVEMBER 2007


CONTINUING EDUCATION: Sanitary Drainage Systems valve in the water line to the drain is the best way to operate the the cover rim to jack the top part of the cleanout up to the finSimpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com flushing-rim drain. Flush valves have been used and save some ished floor level. Floor drains can be furnished with adjustable water; however, they are not as convenient or effective as a shut- tops to attain an installation that is flush with the finished floor. off valve. In any flushing water-supply line to a drain, a vacuum Thermal Expansion breaker installed according to code must be p rovided. When excessive thermal expansion is anticipated, pipe moveKitchen Areas ment should be controlled to avoid harmful changes in slope or When selecting kitchen drains, the designer must know the damage. Anchoring, using expansion joints, or using expansion quantity of liquid and solid waste the drains will be required loops or bends may do this. When anchoring, avoid excessive to accept, as well as which equipment emits waste on a regular stress on the structure and the pipe. Piping or mechanical engibasis and which produces waste only by accidental s pillage. neering handbooks should be consulted if stress analysis is to Floor-cleaning procedures should be ascertained to deter- be performed due to excessive stresses or to the differing expanmine the amount of water used. If any amount of solid waste is sion characteristics of materials. to be drained, receptors must be specified with removable sediProtection from Damage ment buckets made of galvanized or stainless steel. Also, there Following are some common types of damage to anticipate and must be enough vertical clearance over these drains to convesome methods of protection: niently remove the sediment buckets for cleaning. Many kitchen planners mount kitchen equipment on a 5-in. Hazard Protection (125-mm) curb. Placing the drain on top of the curb and under Abrasion Plastic or rubber sleeves. Insulation where copper the equipment makes connection of indirect drain lines diffipipe leaves slab. cult and the receptor inaccessible for inspection and cleaning. Condensation Insulation on piping. Mounting the receptor in front of the curb takes up floor space, Corrosion See Plumbing Engineering Design Handbook, Vol. 1, and the myriad of indirect drains that discharge into it create Ch. 8: Corrosion. a potential hazard for employees who may trip over them. The Earth loads Stronger pipe or pipe sleeves. solution requires close coordination between the engineer and the kitchen designer. Figure 1‑8 shows an arrangement whereby Expansion and Flexible joints, loops, swing joints, or offsets. contraction any spillage in front of the curb can be drained by half of the receptor, while indirect drains are neatly tucked away. Fire Building construction around pipe. Some jurisdictions require metal piping within 2 ft (0.6 m) Where equipment is on the floor level and an indirect waste of an entry into a firewall. Must maintain fire ratings. receptor must be provided under the equipment, a shallow Heat Keeping thermoplastic pipe away from sources of bucket that can easily be removed is recommended. heat or using insulation.

Waterproofing

Whenever a cast-iron drain is cemented into a slab, separation due to expansion and contraction occurs and creates several problems. One is the constant wet area in the crevice around the drain that promotes mildew odor and the breeding of bacteria. Seepage to the floor below is also a possibility. A seepage or flashing flange can correct this problem. Weep holes in the flashing flange direct moisture into the drain. Also, this flange accepts membrane material and, when used, the flashing ring should lock the membrane to the flange. One prevalent misconception about the flashing flange is that it can have weep holes when used with cleanouts. In this case, there can be no weep holes into the cleanout to which the moisture can run. Weep holes should also be eliminated from the flashing flanges of drains, such as reflection-pool drains, where an overflow standpipe to maintain a certain water level shuts off the drain entrance. The term “non-puncturing,” used in reference to membraneflashing, ring-securing methods, is now obsolete, as securing bolts have been moved inboard on flashing L flanges and the membrane need not be punctured to get a seal. Of the various arrangements, this bolting method allows the greatest squeeze pressure on the m embrane.

Floor Leveling A major problem in setting floor drains and cleanouts occurs when the concrete is poured level with the top of the unit, ignoring the fact that the addition of tile on the floor will cause the drain or cleanout to be lower than the surrounding surface. To solve the problem, cleanouts can be specified with tappings in 14 Plumbing Systems & Design

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Nails

Using ferrous pipe, steel sleeves, steel plates, or space pipe away from possible nail penetration zone.

Seismic

Bracing pipe and providing flexible joints at the connection between piping braced to walls or structure and piping braced to the ceiling and between stories (where there will be differential movements).

Settlement

Sleeves or flexible joints. When embedded in concrete, covering with three layers of 15-lb (6.8-kg) felt.

Sunlight

Protecting thermoplastic pipe by insulation and jacket or shading to avoid warping.

Vandals

Installing pipe above reach or in areas protected by building construction. Piping needs to be supported well enough to withstand 250 lb (113.4 kg) hanging on the moving pipe.

Wood Shrinkage

Providing slip joints and shrinkage clearance for pipe when wood shrinks. Approximately 5⁄8 in. (16 mm)/floor is adequate for usual frame construction, based on 4% shrinkage perpendicular to wood grain. Shrinkage along the grain does not usually exceed 0.2%.

Alternate sanitary systems The design and installation of alternative engineered plumbing systems is permitted in all codes. A licensed professional engineer who is responsible for the proper operation of the system must design them. The most important consideration is that if an alternative system is contemplated, submission to, and approval by, the authorities having jurisdiction must be obtained. In order to expedite approval, the following is suggested: 1. Indicate on the design documents that the plumbing system, or parts thereof, is an alternative design. PSDMAGAZINE.ORG

2. Submit enough technical data to support the proposed al- conventional systems. The maximum fixture units that may be Simpo PDF and - http://www.simpopdf.com ternative designMerge and prove theSplit systemUnregistered conforms to the Version intent connected to a branch or stack are also similar to that of convenof the code. This shall include suitability for the intended tional systems. Branch sizes must be increased one size where purpose, strength, equivalent level of performance compared the following exists: to traditional installations, safety, and quality of materials. 1. A second vertical drop or a vertical drop of more than 3 ft 3. The design documents shall include floor plans, riser dia(0.9 m) requires an increase in the downstream side of the grams, and an indication of the proposed flow. connection. 4. Assurance that manufacturers’ installation instructions will be adhered to. Figure 13 (A) Traditional Two-Pipe System, (B) Typical Sovent Single-Stack Plumbing System. 5. If approval is given, the permit and all construction applications shall indicate an alternative engineered design is part of the approved installation. The alternative systems are characterized by, but not limited to, using a single stack for both sanitary and vent or no vent at all. One exception is a conventional drainage, reduced vent system. All of the following described systems have been successfully used in the United States and in other parts of the world for many years and have proven effective in actual use. All of the alternative systems to be discussed have combined sanitary and vent. Because it is considered appropriate, they have been included in the sanitary drainage system chapter.

sovent system The Sovent system was developed in 1959 in Switzerland. It is a patented, single-stack, combination drainage and vent system that uses a single stack instead of a conventional two-pipe drainage and vent stack. The Sovent system uses copper pipe and is suitable only for multistory buildings because it will allow substantial economy in piping installation. Although installed in many countries throughout the world, it remains an alternative, unconventional system with only limited usage in the United States. It shall conform to ANSI B-16.45 and CISMA Standard 177. It is not the intent of this chapter to provide specific design criteria for a Sovent system, but rather to discuss the individual component characteristics that will enable a plumbing engineer to obtain a working knowledge of how the Sovent system works. A typical Sovent-Stack system is illustrated in Figure 13. The entire Sovent system consists of three principal parts: copper DWV piping for all branch wastes and stacks, an aerator fitting at each floor level where the branch waste line connects to the stack, and a deaerator fitting at the base of a stack where a stack enters the house drain. The starting point is the horizontal soil and waste branches. The fixture units and branch sizes are similar to those figures found in

(A)

(B)

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CONTINUING EDUCATION: Sanitary Drainage Systems 2. When three 90-degree changes in direction occur in a hori- that required for drainage purposes alone. The drainage stack Simpobranch, PDF the Merge and Split Unregistered Version - http://www.simpopdf.com zontal horizontal branch shall be increased in and branch piping shall be considered as vents for the drainage size at the upstream side of the third change. system as a whole. Although the pipe sizing is larger in a single3. When a branch serves two water closets and one or more ad- stack system than in a conventional one, installation savings are ditional fixtures, the soil line shall be increased to 4 in. (100 achieved by reducing the amount of vent piping required. The major components of the one pipe system are oversize, mm) at the point where one water closet and one additional unvented S traps instead of the conventionally sized and vented fixture are connected. P traps and fixtures that allow water to run off after the tap is 4. When a soil branch exceeds 12 ft (3.7 m) in horizontal closed to fill the traps with water to maintain the trap seal. The length. trap arm length is limited to reduce any suction buildup, and the 5. When a waste line exceeds 15 ft (4.6 m) in horizontal stack is oversized to limit the internal air pressure and vacuum length. buildup. Stacks must be carried full size through the roof. Two stacks Often referred to as the “Philadelphia” code, this unconvencan be connected at the top above the highest fixture. Two stacks tional system has successfully operated for more than 100 years may also be combined at the bottom prior to entering the build- with no problems. Consideration has been made by code bodies ing drain. The size is based on the total fixture units. Fixtures to include this system as an engineered design, which allows this may be connected into a horizontal offset in a stack below the to be used providing an engineer has designed it in accordance deaerator fitting. with code. For further information, contact the Philadelphia An aerator fitting is required at each level where a soil branch, building department. A riser diagram of a typical Philadelphia a waste line the same size as the stack, or a waste branch one size System is illustrated in Figure 13. smaller than the stack is connected. It consists of an upper stack reduced-size venting inlet, a mixing chamber, and a baffle in the center of the fitting. In 1974, the National Bureau of Standards (NBS) conducted a This provides a chamber where the flow from the branches may laboratory study of one-story and split-level experimental draingradually mix smoothly with the air and liquid already flowage systems where the vents varied from one to six pipes smaller ing in the stack. It also limits the turbulence and velocity of the than those for conventional systems. They showed satisfactory entering water. A 2-in. (50-mm) horizontal branch may enter the hydraulic and pneumatic performance under various loading stack with no fitting. There are two basic styles of aerator fitting conditions. At the same time, the 10-story wet vent system at that meets the needs of most design conditions: the double-side the Stevens Building Technology Research Laboratory had been entry fitting and the single-entry fitting. Face entry and top entry modified by reducing the vents one to three pipe sizes in accorare used in special cases. dance with the plans and specifications of the NBS and reducing A deaerator fitting is required at the bottom of a stack and is the size of the vents. The results also indicated that the vents in designed to overcome the tendency of the falling waste to build a two-story housing unit can safely be made smaller than presup excessive back pressure at the bottom of the stack when the ently allowed without jeopardizing the trap seals. flow is decelerated by the bend into the horizontal drain. It conThis system may allow economies of pipe size in the venting sists of an air separation chamber, a nose piece, a pressure relief design of low-rise residential buildings, although this particuoutlet at the top connected to the building drain, and a stack lar system has not been accepted by authorities. It is limited to outlet at the bottom. The purpose of the deaerator is to separate special conditions and requires the vent pipes be of a material the air flow from the stack and ensure the smooth flow of liquid such as copper or plastic that will resist the buildup of products into the building drain and to relieve the positive pressure genof corrosion. erated at the stack’s base. The configuration of the fitting causes part of the air falling with the liquid to flow through the pres- vacuum drainage system sure relief line, and the remainder of the air goes directly into Vacuum drainage operates on the principal of having the majority of the system under a continuous vacuum. The system is the building drain. There is great importance in explaining the special require- proprietary and is made by various manufacturers. The differments of the Sovent system to the installing contractor. It is ent manufacturers have different names for devices performing probable the contractor is unfamiliar with this system and a similar operations, so generic identification is used. There are complete explanation will be necessary. The engineer should various designs capable of sanitary and waste disposal, either make regular inspections of the project to assure the design separate or in combination, and are used for various projects conditions are met. A complete set of contract documents shall such as prisons, supermarkets, and ships. There is no direct conbe provided to the owner to allow proper alteration or expan- nection from the sanitary waste to the vacuum system. The one big advantage is that piping is installed overhead and no pipe is sion of the project in the future. For additional information and specific sizing contact the required to be placed underground. The system consists of three basic components: a vacuum Copper Development Association. network of piping and other devices that collects and transports single-stack system waste from its origin, vacuum generation pumps, and a vacuum The single-stack system is a combination drainage and vent interface device at the point of origin that isolates the vacuum system consisting of a single stack instead of conventional sepapiping from atmospheric pressure. When the system is to serve rate drainage and vent stacks. This drainage system is one where water closets, the water closets must be purpose made, designed the drainage stack shall serve as both a single-stack drainage to rinse and refill with ½ gallon (2.2 L) of water. and vent system when properly sized. The relief of internal air The piping network for a vacuum waste system is held under pressure depends on making the one-pipe system larger than a constant vacuum between 12 and 18 in. of mercury (in Hg) 16 Plumbing Systems & Design

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(40–65 kPa) and is generally fabricated from PVC, copper, or Simpo PDF Merge and Split Unregistered Version other nonporous, smooth-bore material. Horizontal piping shall slope at a rate of 1/8 in. per foot (1.18 mm) toward the vacuum center. This piping slope is just as it is in conventional systems. If this slope cannot be maintained, the traps created in the piping runs when routed around obstacles would be cleared because of the differential pressure that exists between the vacuum center and the point of origin. The discharge of the piping system is into the waste storage tanks. The vacuum generation system includes the vacuum pumps that create a vacuum in the piping and storage tanks that collect and discharge the waste into the sewer system. The vacuum pumps run only on demand and redundancy is provided. They also have sewage pumps that pump the drainage from the storage tank(s) into the sewer. The vacuum interface is different for sanitary drainage than for clear waste similar to that of supermarkets. Water closet and gray water waste are separate. The vacuum toilets operate instantly upon flushing. When a vacuum toilet is cycled, a discharge control panel assembly is activated sending the discharge to the tank. A valve acts as an interface between the vacuum and the atmosphere controls gray water. It is designed to collect a given amount of the water and then activate, sending the drainage into the tank. The tank will discharge into the sewer when a predetermined level is reached. When clear water is discharged from a project like a supermarket, the water from cases, etc. goes into an accumulator. When a controller senses sufficient waste is present, it opens the normally closed extraction valve, which separates the atmospheric pressure from the vacuum, and removes the waste from the accumulator. Because the vacuum toilets use 0.5 gallon/flush as compared to 3.5 gallons/flush (1.9 L to 13 L) from a conventional system, the holding tanks could be smaller. There is also a flush control panel designed to provide all the control functions associated with vacuum toilets. The control panel consists of a flush valve, flush controller, water valve, and vacuum breaker. All controls are pneumatically operated. The flush controller controls the opening of the flush valve and the rinse valve as well as the duration of the time the flush valve is open. ✺


References 1. Daugherty, Robert L., Joseph B. Franzini, and E. John Finnemore. 1985. Fluid mechanics with engineering applications. 8th ed. New York: McGraw-Hill. 2. Dawson, F.M., and A.A. Kalinske. 1937. Report on hydraulics and pneumatics of plumbing drainage systems. State University of Iowa Studies in Engineering, Bulletin no. 10. 3. Wyly and Eaton. 1950. National Bureau of Standards, Housing and Home Finance Agency.

NOVEMBER 2007


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson

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About This Issue’s Article The November 2007 continuing education article is “Sanitary Drainage Systems,” Chapter 1 of ASPE’s Plumbing Engineering Design Handbook Volume 2: Plumbing Systems. The purpose of the sanitary drainage system is to remove effluent discharged from plumbing fixtures and other equipment to an approved point of disposal. A sanitary drainage system generally consists of horizontal branches, vertical stacks, a building drain inside the building, and a building sewer from the building wall to the point of disposal. The discussion in this chapter centers only on the design of drain and waste systems. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Sanitary Drainage Systems” (PSD 142) 1. A vertical pipe that carries away clear water waste from equipment and non-sanitary fixtures is called a _________. a. sanitary stack b. soil stack c. waste stack d. water stack 2. The generally accepted pressure in a sanitary drainage system is _________. a. +/– 0.1 inch of water column b. +/– 1 inch of water column c. +/– 10 inches of water column d. +/– 100 inches of water column 3. Who originally proposed using drainage fixture units to represent a fixture’s load-producing effect on the plumbing system? a. F.M. Dawson b. Wyly and Eaton c. Roy B. Hunter d. none of the above

PSD 142


7. Cleanouts should be provided _________. a. at the base of all stacks b. at every change in direction greater than 45 degrees c. at the roof stack terminal d. all of the above 8. Which of the following is not a basic floor drain component? a. sediment bucket b. removable grate c. air-admittance valve d. cast drain body with sump

9. In a basic floor drain assembly, the _________ prevents water from passing around the drain to the area below. a. flashing ring b. sediment bucket c. grate d. strainer

4. What is the recommended drainage fixture unit load for a single lavatory? a. 1, b. 2, c. 3, d. 4

10. The recommended material for a sediment bucket is _________. a. bronze b. galvanized steel c. stainless steel d. all of the above

5. Which common formula for calculating flow in pipes is meant for open-channel flow? a. Hazen and Williams b. Manning c. Darcy-Weisbach d. none of the above

11. Which of the following pipe materials offers excellent noise absorption? a. ABS b. cast iron c. PVC d. galvanized steel

6. Which of the following is designed to transport sanitary waste and larger solids suspended in the effluent? a. storm sewer b. sump pump c. ejector pump d. manhole

12. The single-stack system is also referred to as the _________ system. a. Sovent b. Philadelphia c. vacuum drainage d. none of the above


NOVEMBER 2007

PSDMAGAZINE.ORG

Simpo PDFSystems Merge and Unregistered Version - http://www.simpopdf.com Plumbing &Split Design Continuing Education Application Form This form is valid up to one year from date of publication. The PS&D Continuing Education program is approved by ASPE for up to one contact hour (0.1 CEU) of credit per article. Participants who earn a passing score (90 percent) on the CE questions will receive a letter or certification within 30 days of ASPE’s receipt of the application form. (No special certificates will be issued.) Participants who fail and wish to retake the test should resubmit the form along with an additional fee (if required). 1. Photocopy this form or download it from www.psdmagazine.org. 2. Print or type your name and address. Be sure to place your ASPE membership number in the appropriate space. 3. Answer the multiple-choice continuing education (CE) questions based on the corresponding article found on www.psdmagazine.org and the appraisal questions on this form. 4. Submit this form with payment ($35 for nonmembers of ASPE) if required by check or money order made payable to ASPE or credit card via mail (ASPE Education Credit, 8614 W. Catalpa Avenue, Suite 1007, Chicago, IL 60656) or fax (773-695-9007). Please print or type; this information will be used to process your credits. Name _ __________________________________________________________________________________________________ Title _______________________________________________ ASPE Membership No.____________________________________ Organization _ ____________________________________________________________________________________________ Billing Address ____________________________________________________________________________________________ City_ _______________________________________ State/Province________________________ Zip _ ____________________ Country____________________________________________ E-mail_________________________________________________ Daytime telephone_ _________________________________ Fax___________________________________________________

I am applying for the following continuing education credits:




Signature Expiration date: Continuing education credit will be given for this examination through NOVEMBER 30, 2008. Applications received after that date will not be processed.



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CEU. Sanitary Drainage Systems (PSD 142)



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Appraisal Questions

Sanitary Drainage Systems (PSD 142) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No 6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________ 1. 2. 3. 4. 5.

NOVEMBER 2007



PSD 130

Valves



PSDMAGAZINE.ORG


Valves

Valves serve the purpose of controlling the fluids in building service piping. They come in many shapes, sizes, design types, and materials to accommodate different fluids, piping, pressure ranges, and types of service. Proper selection is important to ensure the most efficient, cost-effective, and long-lasting systems. No single valve is best for all services. This chapter is limited to manually operated valves that start, stop, and regulate flow, and prevent its reversal.

Functions Valves are designed to perform four principal functions: 1. Starting and stopping flow 2. Regulating (throttling) flow 3. Preventing the reversal of flow 4. Regulating or relieving the flow pressure.

Service Considerations 1. Pressure 2. Temperature 3. Type of fluid A. Liquid B. Gas, i.e., steam or air C. Dirty or abrasive (erosive) D. Corrosive 4. Flow A. On-off B. Throttling C. Need to prevent flow reversal D. Concern for pressure drop E. Velocity 5. Operating conditions A. Frequency of operation B. Accessibility C. Overall space/size available D. Manual or automated control E. Need for bubble-tight shut-off F. Concerns about body joint leaks G. Fire safe design H. Speed of closure.

Approvals 1. 2. 3. 4.

Manufacturers Standardization Society (MSS) Fire protection: UL and Factory Mutual (FM) State and local codes American Petroleum Industries (API).

Types of Valve Gate Valve With starting and stopping flow its prime function, the gate valve is intended to operate either fully open or fully closed. When fully open, it has the least resistance to flow of all the valve types. From an examination of Figure 1, it becomes readily apparent how the gate valve got its name. A gate-like disc, actuated by a stem screw and hand wheel, moves up and down at right angles to the path of flow and seats against two faces to shut off flow. As the disc of the gate valve presents a flat surface to the oncoming flow, this valve is not suited for regulating or throttling flow. Flow through

a partially open gate valve cre- Figure 1 Gate Valve ates vibration and chattering and subjects the disc and seat to inordinate wear. There is a wide variety of seats and discs to suit the conditions under which the valve is to operate. For relatively low pressures and temperatures and for ordinary fluids, seating materials are not a particularly difficult problem. Bronze and iron valves usually have bronze or bronze-faced seating surfaces; iron valves may be all iron. Nonmetallic “composition” discs are available for tight seating or hard-to-hold fluids, such as air and gasoline. Gate discs can be classified as solid-wedge discs, double discs or split-wedge discs. In the solid-wedge design, a single tapered disc, thin at the bottom and thicker at the top, is forced into a similarly shaped seat. In the double and split-wedge disc designs, two discs are employed back to back, with a spreading device between them. As the valve wheel is turned, the gate drops into its seat (as with any other gate valve), but on the final turns of the wheel, the spreader forces the discs outward Figure 2 Globe Valve against the seats, effecting tighter closure. Bypass valves should be provided where the differential pressure exceeds 200 psi (1378 kPa) on valves sized 4 to 6 in. (101.6 to 152.4 mm), and 100 psi (689 kPa) on valves 8 in. (203.2 mm) or larger. Bypass valves should be ½ in. (12.7 mm) for 4-in. (101.6-mm) valves, and ¾ in. (19.1 mm) for 5-in. (127-mm) valves or larger.

Globe Valve The globe valve (which is named for the shape of its body) is much more resistant to flow than the gate valve, as can be seen by examining the path of flow through it (Figure 2). Its main advantages over the gate valve are

Reprinted from American Society of Plumbing Engineers Data Book Volume 4: Plumbing Components and Equipment, Chapter 3: Valves. © 2003, American Society of Plumbing Engineers.

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Plumbing Systems & Design • Nov/Dec 2005

Simpo PDF Merge Split Unregistered Version - http://www.simpopdf.com its use as a throttling valve toand regulate flow required. It is manufactured in nominal diamAngle Valve and its ease of repair. Very much akin to the globe valve, the angle eters from 1 to 72 in. (25.4 to 1828.8 mm). Because all contact between seat and valve (Figure 3) can cut down on piping In addition to its tight closing, one of the disc ends when flow begins, the effects of installation time, labor, and materials by valve’s advantages is that it can be placed wire drawing (seat erosion) are minimized. serving as both valve and 90° elbow. It is into a very small space between pipe flanges. The valve can operate just barely open or less resistant to flow than the globe valve, as It is available with several types of operator, fully open with little change in wear. Also, flow must change direction twice instead of motorized and manual, and a variety of combecause the disc of the globe valve travels a three times. It is also available with conven- ponent material combinations. relatively short distance between fully open tional, plug type, or composition discs. Screwed-lug type valves should be proand fully closed, with fewer turns of the vided so that equipment may be removed Ball Valve wheel required, an operator can gauge the without draining down the system. The ball valve derives its name from the rate of flow by the number of turns of the drilled ball that swivels on its vertical axis Check Valve wheel. and is operated by a handle, as shown in Swing checks and lift checks are the most As with the gate valve, there are a number Figure 4. Its advantages are its straight- common forms of check valve. Both are of disc and seat arrangements. These are through flow, minimum turbulence, low designed to prevent reversal of flow in a classified as conventional disc, plug type, torque, tight closure, and compactness. Also, pipe. The swing check, Figure 6, permits and composition disc. a quarter turn of the handle makes it a quick- straight-through flow when open and is, The conventional disc is relatively flat, therefore, less resistant to flow than with beveled edges. On closure it the lift check. is pushed down into a beveled, cir- Figure 4 Ball Valve Note: A word of caution regardcular seat. ing the swing check: There have Plug type discs differ only been instances when a swing check in that they are far more tapered, stayed open a few seconds after the thereby increasing the contact surreversal of flow began, allowing the face between disc and seat. This velocity of backflow to rise to such characteristic has the effect of a point that, when closure finally increasing their resistance to the did occur, it was instantaneous and cutting effects of dirt, scale, and the resulting shock to the valve other foreign matter. and system caused serious damage. The composition disc differs Good insurance against such a posfrom the others in that it does not sibility is a lever and weight or a fit into the seat opening but over closing or -opening valve. Reliability, ease of spring to ensure immediate closure upon it, much as a bottle cap fits over the bottle maintenance, and durability have made the reversal of flow. opening. This seat adapts the valve to many ball valve popular in industrial, chemical, services, including use with hard-to-hold Figure 6 Swing Check and gas transmission applications. substances such as compressed air, and makes it easy to repair. Butterfly Valve Figure 5 illustrates a butterfly valve, the valve most commonly used in place of a gate valve Figure 3 Angle Valve in cases where absolute, bubble-free shut-off is Figure 5 Butterfly Valve

The lift check, Figure 7, is primarily for use with gases or compressed air or in fluid systems where pressure drop is not critical.

Valve Materials A single valve may be constructed of several materials. It may have a bronze body, a monel seat, and an aluminum wheel. Material specifications depend on the operating conditions.

Nov/Dec 2005 • Plumbing Systems & Design

51

Continuing Education: Valves Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com valuable for piping subjected to stresses and Bonnets

Figure 7 Lift Check

shocks.

Stainless Steel For highly corrosive fluids, stainless steel valves provide the maximum corrosion resistance, high strength, and good wearing properties. Seating surfaces, stems, and discs of stainless steel are suitable where foreign materials in the fluids handled could have adverse effects.

Valve Ratings

Brass and Bronze Brass usually consists of 85% copper, 5% lead, 5% tin, and 5% zinc. Bronze has a higher copper content, ranging from 86 to 90%, with the remaining percentage divided among lead, tin, and zinc. Of particular importance is the zinc content. Industry maximum is set at 15%, but certain military and government specifications allow no more than 6%. Under certain circumstances, a phenomenon known as “dezincification” will occur in valves or pipes containing zinc. The action is a result of electrolysis; in effect, the zinc is actually drawn out and removed from the brass or bronze, leaving a porous, brittle, and weakened material. The higher the zinc content, the greater the susceptibility to dezincification. To slow or prevent the process, tin, phosphorus antimony, and other inhibitors are added. Brass valves should not be used for operating temperatures above 450°F (232.2°C). The maximum for bronze in 550°F (287.8°C).

Iron Iron used in valves usually conforms to ASTM Standard A26. Although iron-bodied valves are manufactured in sizes as small as ¼-in. (6.4-mm) nominal diameter, they are most commonly stocked in sizes of 2 in. (50.8 mm) and above. In these larger sizes, they are considerably less expensive than bronze. The higher weight of iron valves, as compared to bronze valves, should be considered when figuring hanger spacing and loads. A typical 2-in. (50.8-mm) screwed, bronze, globe valve rated at 125 psi (861.3 kPa) weighs about 13 lb (5.9 kg). The same valve in iron weighs 15 lb (6.8 kg) and, if specified with a yoke bonnet, about 22 lb (10 kg).

Malleable Iron Malleable iron valves are stronger, stiffer, and tougher than iron-bodied valves and hold tighter pressures. Toughness is most

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Most valve manufacturers rate their products in terms of saturated steam pressure; or pressure of nonshock cold water, oil, or gas (WOG); or both. These ratings usually appear on the body of the valve. For instance, a valve with the markings “125” with “200 WOG” will operate safely at 125 psi (861.3 kPa) of saturated steam or 200 psi (1378 kPa) cold water, oil, or gas. The engineer should be familiar with the markings on the valves specified and should keep them in mind during construction inspection. A ruptured valve can do much damage.

Valve Components Stems Stem designs fall into four basic categories: rising stem with outside screw, rising stem with inside screw, nonrising stem with inside screw, and sliding stem. Rising stem with outside screw This design is ideal where the valve is infrequently used and the possibility of sticking would constitute a hazard, such as in a fire-protection system. In this arrangement, the screws are not subject to corrosion or elements in the line fluid that might cause damage because they are outside the valve body. Also, being outside, they can easily be lubricated. As with any other rising stem valve, sufficient clearance must be allowed to enable a full opening. Rising stem with inside screw This design is the simplest and most common stem design for gate, globe, and angle valves. The position of the hand wheel indicates the position of the disc, opened or closed. Nonrising stem These are ideal where headroom is limited. They are generally limited to use with gate valves. In this type, the screw does not raise the stem but rather raises and lowers the disc. As the stem only rotates and does not rise, wear on packings is slightly lessened. Sliding stem These are applied where quick opening and closing are required. A lever replaces the hand wheel, and stem threads are eliminated.


In choosing valves, the service characteristics of the bonnet joint should not be overlooked. Bonnets and bonnet joints must provide a leakproof closure for the body. There are many modifications, but the three most common types are screwed-in bonnet, screwed union-ring bonnet, and bolted bonnet. Screwed-in bonnet This is the simplest and least expensive construction, frequently used on bronze gate, globe, and angle valves and recommended where frequent dismantling is not needed. When properly designed with running threads and carefully assembled, the screwed-in bonnet makes a durable, pressure-tight seal that is suited for many services. Screwed union-ring bonnet This construction is convenient where valves need frequent inspection or cleaning—also for quick renewal or changeover of the disc in composition disc valves. A separate union ring applies a direct load on the bonnet to hold the pressure-tight joint with the body. The turning motion used to tighten the ring is split between the shoulders of the ring and bonnet. Hence, the point of seal contact between the bonnet and the body is less subject to wear from frequent opening of the joint. Contact faces are less likely to be damaged in handling. The union ring gives the body added strength and rigidity against internal pressure and distortion. While ideal on smaller valves, the screwed, union-ring bonnet is impractical on large sizes. Bolted bonnet joint A practical and commonly used joint for larger size valves or for higher-pressure applications, the bolted bonnet joint has multiple boltings with smaller diameter bolts that permit equalized sealing pressure without the excessive torque needed to make large threaded joints. Only small wrenches are needed.

End Connections Valves are available with screwed, welded, brazed, soldered, flared, flanged, and hub ends.

Screwed End This is by far the most widely used type of end connection. It is found in brass, iron, steel, and alloy piping materials. It is suited for all pressures but is usually confined to smaller pipe sizes. The larger the pipe size, the more difficult it is to make up the screwed joint.

Welded End This type of end is available only in steel valves and fittings and is mainly for higherpressure and -temperature services. It is rec-

Simpofor PDF and Split Unregistered Version ommended linesMerge not requiring frequent ASME American Society -ofhttp://www.simpopdf.com Mechanical Clapper A common term that is used dismantling. There are two types of welded Engineers to describe the disc of a swing type, check end materials: butt end socket welding. Butt- ASTM American Standard for Testing and valve. welding valves and fittings come in all sizes; Material Disc The disc-shaped device that is socket-welding ends are usually limited to AWWA American Water Works Association attached to the bottom of the stem and that smaller sizes. BUNA-N Butadiene and acryloniis brought into contact with or lifted off the trile (nitrile rubber) seating surfaces to close or open a globe Brazed End CSA Canadian Standards Association (also valve or butterfly valve. This is available on brass materials. The ends CSA International) (approval agency for Flanged bonnet A type of bonnet so of such materials are specially designed for AGA) constructed that it attaches to the body the use of brazing alloys to make the joint. CWP Cold working pressure by means of a flanged, bolted connection. When the equipment and brazing material EPDM Ethylene-propylene diene monomer The whole bonnet assembly, including the are heated with a welding torch to the temIBBM Iron body, bronze mounted (trim) hand wheel, stem, and disc, may be quickly perature required by the alloy, a tight seal IS Inside screw removed by unscrewing the nuts from the is formed between the pipe and valve or MSS Manufacturers Standardization Society bonnet stud bolts. fitting. While made in a manner similar to of the Valve and Fittings Industry Gate valve A valve that is used to open a solder joint, a brazed joint can withstand NBR Acrylonitrile-butadiene rubber or close off the flow of fluid through a pipe. higher temperatures due to the brazing NFPA National Fire Protection Association It is so named because of the wedge (gate) materials used. NRS Nonrising stem that is either raised out of or lowered into a Soldered Joint OS&Y Outside screw and yoke double-seated sluice to permit full flow or This is used with copper tubing for plumb- PSI Pounds per square inch completely shut off flow. The passageway ing and heating lines and for many low-pres- PTFE Polytetrafluoroethylene plastic through a gate valve is straight through, sure industrial services. The joint is soldered RS Rising stem uninterrupted, and is the full size of the by applying heat. Because of close clearance SWP Steam working pressure pipeline into which the valve is installed. between the tubing and the socket of the fit- TFE Tetrafluoroethylene plastic Gland bushing A metal bushing installed ting or valve, the solder flows into the joint WCB Wrought carbon, grade B between the packing nut and the packing to by capillary action. The use of soldered joints WOG Water, oil, gas (cold working prestransmit the force exerted by the packing nut under high temperatures is limited because sure) against the packing. of the low melting point of the solder. Silver WWP Water working pressure Globe valve A valve that is used for throtsolder or silfos are used for higher pressures tling or regulating the flow through a pipe. Glossary and temperatures. It is so named because of the globular shape Ball A valve consisting of a single drilled of the body. The disc is raised off a horizonFlared End ball that is operated by a handle attached tal seating surface to permit flow or lowered This is commonly used on valves and fit- to the vertical axis of the ball, which peragainst the horizontal seating surface to shut tings for metal and plastic tubing up to 2 in. mits fluid flow in a straight-through direcoff flow. The disc may be lifted completely (50.8 mm) diameter. The end of the tubing tion. The ball within the valve body may be to permit full flow or lifted only slightly to is skirted or flared and a ring nut is used to rotated fully opened or fully closed by one throttle or regulate flow. The flow through a make a union type joint. quarter turn of the handle. globe valve has to make two 90° turns. Body That part of the valve that attaches Flanged End Hand wheel The wheel-shaped turning to the pipeline or equipment—with screwed This is generally used when screwed ends device by which the stem is rotated, thus liftends, flanged ends, or soldered/welded joint become impractical because of cost, size, ing or lowering the disc or wedge. ends—and encloses the working parts of the strength of joint, etc. Flanged ends are genHinge pin The valve part that the disc or valve. erally used for larger-diameter lines due to clapper of a check valve swings. Bonnet The part of the valve housing ease of assembly and dismantling. Flanged Outside screw and yoke A type of through which the stem extends. It provides facings are available in various designs bonnet so constructed that the operating support and protection to the stem and depending on service requirements. One threads of the stem are outside the valve houses the stem packing. It may be screwed important rule is to match facings. When housing, where they may be easily lubrior bolted to the body. bolting iron valves to forged steel flanges, cated and do not come into contact with the Butterfly A type of valve consisting of the facing should be of the flat face design fluid flowing through the valve. a single disc that is operated by a handle on both surfaces. Packing A general term describing any attached to the disc, which permits fluid flow yielding material used to affect a tight joint. Hub End in a straight-through direction. The valve is This is generally limited to valves for water- bidirectional. The disc within the valve body Valve packing is generally “jam packing”; it is supply and sewage piping. The joint is may be rotated fully open or fully closed by pushed into a stuffing box and adjusted from time to time by tightening down a packing assembled on the socket principle, with the one quarter turn of the handle. gland or packing nut. pipe inserted in the hub end of the valve or Cap The top part of the housing of a Packing gland A device that holds and fitting then caulked with oakum and sealed check valve (equivalent to the bonnet of a compresses the packing and provides for with molten lead. gate or globe valve), which may be either additional compression by manual adjustscrewed or bolted onto the main body. Abbreviations ment of the gland as wear of the packing Check valve An automatic, self-closing AGA American Gas Association occurs. A packing gland may be screwed or valve that permits flow in only one direcAISI American Iron and Steel Institute bolted in place. ANSI American National Standards Institute tion. It automatically closes by gravity when Packing nut A nut that is screwed into liquid ceases to flow in that direction. API American Petroleum Institute place and presses down upon a gland bushing, which transmits the force exerted by


53

Continuing Education: Valves PDF Merge and SplittheUnregistered Version - http://www.simpopdf.com the Simpo packing nut to the packing. It serves Union threaded piece That part of the Design Detail: Gate Valves same purpose as the packing gland. union that is fastened to the pipe and has Advantages and Recommendations Rising stem A threaded component that external threads over which the union ring 1. Good choice for on-off service is unscrewed or screwed through the bonnet is screwed to effect a coupling. to open or close the valve. The hand wheel Wedge (See also disc.) The wedge-shaped 2. Full flow, low pressure drop may rise with the stem, or the stem may rise device that fits into the seating surfaces of a 3. Bidirectional through the hand wheel. gate valve and that is drawn out of contact 4. Bypass valves should be provided Screwed bonnet A type of bonnet so with the seating surfaces to permit flow or is where the differential pressure exceeds constructed that it attaches to the body by pushed down into contact with the seating 200 psi on valves 4½ to 6 in. and 100 means of a screwed joint. A bonnet may be surfaces to close off flow with the valve. psi on valves 8 in. and larger. Bypass attached to the body by screwing over the 100% area (full port) The area through valves should be ½ in. for 4-in. valves body or inside the body, or by means of a the valve is equal to or greater than the area and ¾ in. for 5-in. valves or larger. union type, screwed connection. of standard pipe. Disadvantages Solid wedge A wedge consisting of one MSS Standard Practices 1. Not for throttling: Use fully open or fully solid piece into which the valve stem is closed. Flow through a partially open attached, so it seals against the valve seat- Number gate valve causes vibration and chating surfaces to ensure a tight seal when the SP-25 Standard Marking System for Valves, tering and subjects the disc and seat to valve is closed. Fittings, Flanges and Unions inordinate wear. Split wedge A wedge consisting of two SP-42 150 lb. Corrosion Resistant Cast pieces into which the valve stem is screwed, 2. Metal-to-metal seating means not best Flanged Valves so it expands the two pieces against the choice for frequent operation. Bubblevalve seating surfaces to ensure a tight seal SP-67 Butterfly Valves tight seating should not be expected when the valve is closed. with metal-to-metal design. SP-70 Cast Iron Gate Valves, Flanged and Standard port The area through the 3. Difficult to automate. Threaded Ends valve is less than the area of standard pipe. Stem The usually threaded shaft to which SP-71 Cast Iron Swing Check Valves, Flanged Disc and Seat Designs and Threaded Ends 1. Bronze or bronze-faced seating surfaces is attached the hand wheel at the top and are used with bronze and iron valves. the disc or wedge at the lower end. The stem SP-72 Ball Valves with Flanged or Butt-WeldIron valves may use all-iron seating may also be called the “spindle.” ing Ends for General Service surfaces. These are preferred for low Stop plug An adjusting screw that extends SP-78 Cast Iron Plug Valves pressures and temperatures and for through the body of a check valve. It adjusts ordinary fluids. Stainless steel is used for and controls the extent of movement of the SP-80 Bronze Gate, Globe, Angle and Check Valves high-pressure steam and erosive media. disc or clapper. Swing check valve A check valve that SP-81 Stainless Steel, Bonnetless, Flanged, 2. Nonmetallic, “composition” discs are uses a hinged disc or clapper to limit the Wafer, Knife Gate Valves available for tight seating or hard-todirection of flow. The pressure exerted by hold fluids, such as air and gasoline. SP-82 Valve Pressure Testing Methods the fluid flowing through the valve forces 3. Solid-wedge disc design is thinner at the the disc away from the seating surface. SP-85 Cast Iron Valves bottom, thicker at the top, and forced When the flow ceases, the clapper falls to SP-110 Ball Valves into the seat of a similar shape. its original position, preventing flow in the Notes: 1. Use of the last approved revi- 4. Double-disc or split-wedge disc design opposite direction. sion of all standards shall be used. 2. A are two discs employed back to back Union A coupling fitting consisting of large number of former MSS Standard Pracwith a spreading device between them. three parts (a shoulder piece, a thread piece, tices have been approved by the American As the valve wheel is turned, the gate and a ring) that is used for coupling the ends National Standards Institute (ANSI) as ANSI drops into its seat (as with any other of pipe sections. Adjoining faces of shoul- Standards. To maintain a single source of gate valve), but on the final turns of the der and thread pieces are lapped together authoritative information, MSS withdraws its wheel, the spreader forces the discs outto form a tight joint. Unions permit easy Standard Practices when they are approved ward against the seats, effecting tighter disconnection for repair and replacement of as ANSI Standards. closure. piping and fittings. 5. Resilient wedge is a rubber encapsuValve Design Choices Union bonnet A type of bonnet that is lated metal wedge that seals against an so constructed that the whole bonnet assem- 1. Multiturn type epoxy-coated body. Resilient wedge is A. Gate bly, including the hand wheel, stem, and limited to cold-water applications. B. Globe/angle-globe disc assembly, may be quickly removed by C. End connection unscrewing the bonnet union ring from the Design Detail: Globe/Angle-Globe 2. Check type (backflow prevention) valve body. Valve Union ring A large nut-like component A. Swing Advantages and Recommendations that secures the union thread and the union B. Lift 1. Recommended for throttling applicashoulder together. It slips over and against C. Silent or nonslam tions. the shoulder piece and screws onto the D. End connection union thread piece. 2. Positive bubble-tight shut-off when 3. Quarter-turn type Union shoulder piece A part of the equipped with resilient seating. A. Ball union fastened to the pipe that retains the 3. Good for frequent operation. B. Butterfly-resilient seated union ring. C. Plug 4. Easy to repair. D. End connection. 54


Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com in. copper tubing. Care must be taken Design Detail: Quarter-Turn Ball

Disadvantages

1. Flow path causes a significant pressure drop. 2. Globe valves are more costly than alternative valves.

Disc and Seat Designs 1. Resilient (soft) seat discs are preferred over metal-to-metal except where temperatures, very close throttling or abrasive flow make all-metal seating a better choice. Stainless steel trim is available for medium- to high-pressure steam and abrasive applications. Tetrafluoroethylene (TFE) is the best resilient disc material for most services, although rubber’s softness gives good performance in cold water. TFE is good up to 400°F. Butadiene and acrylonitrile (Buna-N) is good up to 200°F. 2. Automatic, steam, stop-check, angleglobe valves are best on medium-pressure steam service. 3. Where the sliding action of the semiplug disc assembly permits the valve to serve as a shut-off valve, throttling valve, and or a check valve.

Design Detail: Check Valves (Backflow Prevention) 1. Swing type check valves offer the least pressure drop and offer simple automatic closure; when fluid flow stops, gravity and flow reversal close the valve. Many bronze valves offer a Y-pattern body with an angle seat for improved performance. Resilient Teflon seating is preferred for tighter shut-off. 2. Lift checks come in an in-line or globestyle body pattern. Both cause greater pressure drop than the swing type, with the horizontal pattern similar in restriction to globe valves. 3. Some styles are spring actuated and center guided for immediate closure when flow stops. The in-line, springactuated lift check is also referred to as the “silent check” because the spring closes the valve before gravity and fluid reversal can slam the valve closed. Resilient seating is recommended. 4. Double-disc check valves have twin discs on a spring-loaded center shaft. These valves have better flow characteristics than lift checks and most often use a wafer body for low cost and easy installation. Resilient seating is recommended.

Valves

Advantages and Recommendations 1. Bubble-tight shut-off from resilient (TFE) seats 2. Quick, 90° open/close, not torque dependent for seating 3. Straight-through, unobstructed flow, bidirectional 4. Easier to automate than multiturn valves 5. More compact than multiturn valves 6. Offer long cycle life.

Disadvantages 1. Temperature and pressure range limited by seat material. 2. Cavity around ball traps media and does not drain entrapped media. Susceptible to freezing, expansion, and increased pressure due to increased temperature.

Body Styles 1. One-piece valves have no potential body leak path but have a double reduced port, thus, significant pressure drop occurs. Not repairable, they are used primarily by chemical and refining plants. 2. Two-piece end entries are used most commonly in building services. They are the best value valves and are available in full- or standard-port balls. They are recommended for on-off or throttling service and not recommended to be repaired. 3. Three-piece type valves are more costly but are easier to disassemble and offer the possibility of in-line repair. They are available in full- or standard-port balls.

Port Size 1. Full-port ball valves provide a pressure drop equal to the equivalent length of the pipe, slightly better than gate valves. 2. Standard- (conventional-) port balls are up to one pipe size smaller than the nominal pipe size but still have significantly better flow characteristics than globe valves. 3. Reduced-port ball valves have greater than one pipe size flow restriction and are not recommended in building services piping but rather are used for process piping for hazardous material transfer.

End Connections 1. Threaded ball valves with ANSI female taper threads are most commonly used with pipe up to 2 in. 2. Soldered-end valves permit the direct connection of bronze ball valves to 2-

not to overheat and damage the valves during the soldering process.

Handle Extensions 1. Insulated handle extensions or extended handles should be used to keep insulated piping systems intact.

Design Detail: Quarter-Turn Butterfly Valves Advantages and Recommendations 1. Bubble-tight shut-off from resilient seats 2. Quick, 90° open/close; easier to automate than multiturn valves 3. Very cost-effective compared to alternative valve choices 4. Broad selection of trim materials to match different fluid conditions 5. More compact than multiturn valves 6. Offer long cycle life 7. Dead-end service.

Disadvantages 1. Not to be used with steam. 2. Gear operators are needed for 8 in. and larger valves to aid in operation and protect against operating too quickly and causing destructive line shock.

Body Styles 1. Wafer style valves are held in place between two pipe flanges. They are easy to install but cannot be used as isolation valves. 2. Lug-style valves have wafer bodies but tapped lugs matching up to bolt circles of class 125/150-lb flanges. They are easily installed with cap screws from either side. Lug style designs from some manufacturers permit dropping the pipe from one side while the valve holds full pressure if needed. 3. Groove butterfly valves directly connect to pipe using iron-pipe-size, grooved couplings. While more costly than wafer valves, grooved valves are the easiest to install.

Design Detail: Quarter-Turn Valves, Lubricated Plug Cocks Advantages and Recommendations 1. Bubble-tight shut-off from stem seal of reinforced Teflon. Leakproof, springloaded ball and lubricated, sealed check valve and combination lubricant screw and button head fitting prevent foreign matter from being forced into the lubrication system. 2. Quick, 90° open/close, not dependent on torque for seating.


55

Continuing Education: Valves Simpo PDF Merge andflow, Split Unregistered Version - http://www.simpopdf.com 3. Straight-through, unobstructed ¼–1 in., conventional-port 1¼–2 in., blow- steam service. For class 150 seat disc, specify bidirectional flow, three-way flow, or out-proof stems, chrome-plated brass ball, TFE for steam service. four-way flow. and threaded or soldered ends. Valves shall 2½ in. and larger Valves 2½ in. and comply with MSS SP-110 larger shall be class 125, rated 125 psi SWP, 4. Offers long cycle life. 200 psi nonshock CWP; iron body, bronze 5. Adjustable stop for balancing or throtGlobe valves mounted, with body and bolted bonnet contling service. 2 in. and smaller Valves 2 in. and smaller forming to ASTM A-126 class B cast-iron, shall be of class 125, rated 125 psi SWP, 200 flanged ends, swing type disc, and nonas6. Can be supplied with round, diamond, psi nonshock CWP; body and bonnet shall bestos gasket. Valves shall comply with MSS or rectangular (standard) plug. be of ASTM B-62 cast-bronze composition SP-71. 7. Mechanism for power operation or with threaded or soldered ends. Stems shall remote control of any size and type to Alternative check valves (2½ in. and be of dezincification-resistant silicon bronze, larger) shall be class 125/250 iron body, operate with air, oil, or water. ASTM B-371, or low-zinc alloy, ASTM B-99. bronze mounted, wafer check valve, with Disadvantages Packing glands shall be of bronze, ASTM B- ends designed for flanged type connection, 1. Temperature and pressure range limited 62, with aramid fiber, nonasbestos packing, aluminum bronze disc, EPDM seats, 316 by type of lubricant sealant and ANSI complete with malleable hand wheel. Valves stainless steel torsion spring, and hinge pin. Standard rating, i.e. 150 psi steam workshall comply with MSS SP-80. A spring-actuated check valve is to be ing pressure (SWP) and 200 psi non2½ in. and larger Valves 2½ in. and used on pump discharge. Swing check with shock, cold working pressure (CWP), larger shall be class 125, rated 125 psi SWP, outside lever and spring (not center guided) and water, oil, gas (WOG). 200 psi nonshock CWP; and have an iron is to be used on sewage ejectors or stormbody, bronze-mounted OS&Y, with body water sump pumps. General Valve Specification by Service and bolted bonnet conforming to ASTM A-126 class B cast-iron, flanged ends, with Fire-Protection System Hot and Cold Domestic Water Service aramid fiber, nonasbestos packing, and twoGate valves Gate valve piece packing gland assembly. Valves shall 2 in. and smaller Valves 2 in. and 2 in. and smaller Valves 2 in. and smaller comply with MSS SP-85. smaller shall be of class 175 psi water workshall be class 125, rated 125 psi SWP, 200 ing pressure (WWP) or greater, with body psi nonshock CWP, rising stem. Body, union Butterfly valves 2½ in. and larger Valves 2 ½ in. and and bonnet conforming to ASTM-B-62, castbonnet, and solid wedge shall be of ASTM B-62 cast bronze with threaded ends. Stems larger shall be rated 200 psi nonshock CWP; bronze composition, threaded ends, OS&Y, shall be of dezincification-resistant silicon and have a lug or IPS grooved type body solid disc and listed by UL, FM approved, bronze, ASTM B-371, or low-zinc alloy, ASTM with 2-in. extended neck for insulating. They and in compliance with MSS SP-80. 2½ in. and larger Valves 2½ in. and B-99. Packing glands shall be of bronze, shall be ductile iron, ASTM A 536; with stainlarger shall be rated 175 psi WWP or greater, ASTM B-62, with aramid fiber, nonasbes- less steel disc; 416 stainless steel stem; ethtos packing, complete with malleable hand ylene-propylene diene monomer (EPDM) O- and have an iron body, bronze mounted or ring stem seals; and resilient, EPDM rubber with resilient rubber encapsulated wedge, wheel. Valves shall comply with MSS SP-80. 2½ in. and larger Valves 2½ in. and molded to seat. Sizes 2½ to 6 in. shall be with body and bonnet conforming to ASTM larger shall be class 125, rated 100 psi SWP, lever operated with a ten-position throt- A-126, class B cast-iron, OS&Y, class 125 150 psi nonshock CWP; and have an iron tling plate; sizes 8 to 12 in. shall have gear flanged or grooved ends. If of resilient body, bronze-mounted outside screw and operators; sizes 14 in. and larger shall have wedge design, interior of valve is to be epoxy yoke (OS&Y), with body and bolted bonnet worm gear operators only. They are suitable coated. Valves shall meet or exceed AWWA conforming to ASTM A-126 class B cast-iron, for use as bidirectional isolation valves and, C509-89, Standard for Protective Epoxy Inteflanged ends, with aramid fiber, nonasbestos as recommended by the manufacturer, on rior Coating for Valves. Valves are to be UL packing and two-piece packing gland assem- dead-end service at full pressure without the listed, FM approved, and in compliance with MSS SP-70. need for downstream flanges. bly. Valves shall comply with MSS SP-70. Valves 4 in. and larger for underValves shall comply with MSS SP-67. All domestic water valves 4 in. and larger Note: Butterfly valves in dead-end ser- ground bury shall be rated 200 psi WWP that are buried in the ground shall be iron body, bronze-fitted, with O-ring stem seal; vice require both upstream and downstream or greater, with body and bonnet conand have epoxy coating inside and outside flanges for proper shut-off and retention forming to ASTM A-126, class B cast iron, and a resilient-seated gate valve with non- or must be certified by the manufacturer bronze mounted, resilient-seated gate valve rising stem and mechanical joint or flanged for dead-end service without downstream with nonrising stem, with O-ring stem seal, epoxy coating inside and outside, flanged or ends as required. All valves furnished shall flanges. mechanical joint ends as required. All valves open left. All internal parts shall be accesCheck valves furnished shall open left. All internal parts sible without removing the valve body from 2 in. and smaller Valves 2 in. and smaller shall be accessible without removing the the line. Valves shall conform to AWWA shall be class 125, rated 125 psi SWP, 200 psi valve body from the line. Valves shall conC509-89, Standard for Resilient-Seated nonshock CWP; and have threaded or sol- form to AWWA C509-89, Standard for ResilGate Valves. Epoxy coating shall conform dered ends, with body and cap conforming ient-Seated Gate Valves. Epoxy coating shall to AWWA C550-90, Standard for Protective to ASTM B-62 cast bronze composition, y- conform to AWWA C550-90, Standard for Epoxy Interior Coating for Valves. pattern swing type disc. Valves shall comply Protective Epoxy Interior Coating for Valves. with MSS SP-80 Ball valves Valves shall come complete with mounting Note: Class 150 valves meeting the above plate for indicator post and be UL listed, FM 2 in. and smaller Valves 2 in. and smaller shall be rated 150 psi SWP, 600 psi nonshock specifications may be used where system approved, and in compliance with MSS SPCWP; and have two-piece, cast brass bodies, pressure requires. For class 125 seat disc, 70. replaceable reinforced Teflon seats, full-port specify Buna-N for WOG service and TFE for 56


Simpo PDF aMerge Split Unregistered Version http://www.simpopdf.com When required, vertical and indicator post iron, with flanged ends -for use with class 175 psig working pressure, UL listed, FM may be used on underground valves. Posts 250/300 flanges. They shall be UL listed, FM approved and in compliance with MSS SPmust provide a means of knowing if the approved, and in compliance with MSS SP- 67. valve is open or shut. Indicator posts must 71. Valves furnished shall have ductile-iron be UL listed and FM approved. Note: In New York City, valves are to be ASTM A-536 body, and may have ductile-iron approved by the New York City Materials ASTM A-395 (nickel-plated) discs or alumiHigh-Rise Service and Equipment Acceptance Division (MEA), num bronze discs, depending upon the local in addition to the above specifications. water conditions. In addition, wafer style for Gate valves installation between class 125/150 flanges or 2½- to 12-in. Gate valves 2½ to 10 in. Ball valves lug style or grooved body may be specified, shall be rated 300 psi WWP or greater, 12 2 in. and smaller Valves 2 in. and smaller depending upon the system needs. in. shall be rated 250 psi WWP, and have an shall be constructed of commercial bronze, Valves shall be equipped with weatheriron body, bronze mounted, with body and ASTM B 584, rated 175 psi WWP or higher, proof gear operator rated for indoor/outbonnet conforming to ASTM A-126, class B, with reinforced TFE seats. Valves shall have door use, with hand wheel and raised posicast iron, OS & Y, with flanged ends for use a gear operator with a raised position indi- tion indicator with two internal supervisory with class 250/300 flanges. They shall be UL cator and two internal supervisory switches. switches. listed, FM approved, and in compliance with Valves shall have threaded or IPS grooved Check valves Valves 2½ in. and larger MSS SP-70. ends and shall have blowout-proof stems shall be 500 psi WWP, bolted bonnet, with and chrome-plated balls. They shall be UL body and bonnet conforming to ASTM ACheck valves 2½- to 12-in. Check valves 2½ to 10 in. listed, FM approved, and in compliance with 126, class B cast iron, flanged end with comshall be rated 300 psi WWP or greater, 12 in. MSS SP-110 for fire-protection service. position y-pattern, horizontal, swing type shall be rated 250 psi WWP, and have an iron disc. They shall be UL listed, FM approved, Butterfly valves body, bronze mounted, with a horizontal 4 to 12 in. Butterfly valves may be sub- and in compliance with MSS SP-71 type 1 for swing check design, with body and bonnet stituted for gate valves, where appropri- fire-protection service. n conforming to ASTM A 126 Class B, cast ate. Valves shall be rated for 250 psi WWP,


57

Continuing Education: Valves Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com

Continuing Education from Plumbing Systems & Design Kenneth G.Wentink, PE, CPD, and Robert D. Jackson, Chicago Chapter President Do you find it difficult to obtain continuing education units (CEUs)? Is it hard for you to attend technical seminars? Through Plumbing Systems & Design (PS&D), ASPE can help you accumulate the CEUs required for maintaining your Certified in Plumbing Design (CPD) status. ASPE features a technical article in every issue of PS&D, excerpted from its own publications. Each article is followed by a multiplechoice test and a simple reporting form. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately 1 hour. A nominal processing fee is charged—$25 for ASPE members and $35 for nonmembers (until further notice, the member fee is waived). If you earn a grade of 90% or higher on the test, you will be notified that you have logged

0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for 3 years. No certificates will be issued in addition to the notification letter. You can apply for CEU credit on any technical article that has appeared in PS&D within the past 12 months. However, CEU credit only can be obtained on a total of eight PS&D articles in a 12-month period. Note: In determining your answers to the CE questions, use only the material presented in the continuing education article. Using other information may result in a wrong answer.

CE Questions—“Valves” (PSD 130) 1. Dezincification occurs in valves as a result of _________. a. electrolysis b. high velocity c. high pressure d. water hammer 2. All domestic water gate valves 4 inches and larger that are buried in the ground shall be iron body, bronze fitted with __________. a. o-ring stem seal b. epoxy coating inside and out c. resilient seats d. all of the above 3. MSS withdraws its standard practices when __________. a. they have been revised b. they are approved as ANSI standards c. they are in conflict with local codes d. none of the above 4. The valve type that is best suited for all services is a __________ valve. a. ball b. gate c. globe d. none of the above 5. When a gate valve is fully open, it __________. a. has the highest resistance to flow of all valve types b. has the least resistance to flow of all valve types c. causes water hammer in the piping system d. creates velocity surges 6. Butterfly valves in dead-end service require __________. a. flanges upstream and down stream for shut-off and proper retention b. lock nuts on the flange bolts c. certification by the manufacture for dead-end service without downstream flanges d. a or c but not b

7. Bypass valves should be provided where the differential pressure exceeds __________ psi on valves sized 4-6 inches. a. 100 b. 150 c. 200 d. 250 8. Two-inch and smaller ball valves rated 150 psi SWP, 600 psi non-shock CPW with two-piece, cast brass bodies, replaceable reinforced Teflon seats, blowoutproof stems, chrome plated brass ball and threaded or soldered ends must comply with MSS __________. a. SP-110 b. standard practices c. SP-72 d. all of the above 9. The cap of a check valve is the equivalent to the ______. a. bonnet of a gate or globe valve b. operating pressure c. packing gland of a ball valve d. none of the above 10. By-pass valves __________. a. are required when differential pressure exceeds 200 psi on gate valves 4-6 inches and 100 psi gate valves 8 inches and larger b. must be 2 inches in diameter c. should be provided where the differential pressure exceeds 200 psi on gate valves 4½-6 inches and 100 psi on gate valves 8 inches and larger d. must be ½ inch or ¾ inch only 11. One advantage of the butterfly valve is that it can be placed in very small spaces between __________. a. other valves b. equipment c. piping d. pipe flanges 12. When flow begins in a globe valve, __________. a. wire drawing is minimized b. contact between the seat and disk ends c. a and b above d. none of the above

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Signature Expiration date: Continuing education credit will be given for this examination through November 30, 2006. Applications received after that date will not be processed.



Signature

Valves (PSD 130)



Expiration date


Appraisal Questions Valves (PSD 130) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No 6. How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________ 1. 2. 3. 4. 5.


59

Vent Systems

PSD 137




PSDMAGAZINE.ORG


Vent Systems


Flow of air is the primary consideration in the design of a venting system for the ventilation of the piping and protection of the fixture trap seals of a sanitary drainage system. Since air is of such primary importance, it is essential that the plumbing engineer be familiar with certain physical characteristics that are pertinent to its behavior in a plumbing system. Density of any substance is its mass per unit volume. The density of air is its weight in pounds per cubic foot of volume. The density of air is affected by temperature, moisture content, and pressure. The density of “standard air” is taken at atmospheric pressure and 68.4°F. It is equal to 0.075 lbm/ft3. With a rise in temperature, the density of air decreases and with a lowering of temperature its density increases. The moisture content of air in the plumbing system has a negligible effect on its density and can be disregarded in all calculations. Pressure has an appreciable effect; the higher the pressure the greater the density, and the lower the pressure the less the density. Specific Weight of a fluid is not an absolute property, but depends upon the local gravitational field (gravitational acceleration on earth is g=32.2 ft/sec2) and the properties of the fluid itself. Commonly called “density” when concerning gravitational force, the numerical value of specific weight (lbf/ft3) is equal to density (lbm/ft3). Elasticity is the ability of a substance to assume its original characteristics after the removal of a force that has been applied. Air is a perfectly elastic substance. From the scientific definition of elasticity it becomes clear that a rubber band is really a very inelastic material. If a weight is suspended from a rubber band and left for a few hours, then the weight is removed, the rubber band will spring back, but definitely not to its original length. If a force is applied to air, the force can be applied for days or years, and when it is removed, the air will return exactly to its original condition. Air is compressible. There is an increase in pressure when air is compressed. In the plumbing system, only an extremely small change in pressure can be tolerated. For a pressure of 1 in. of water column (0.036 psi), the volume of air will be compressed by 1∕400 of its original volume. Assuming an original volume of 400 ft3 of air at atmospheric pressure and the application of a pressure of 1 in. of water column, the air will be compressed by 400 × 1∕400 = 1 ft3. It is obvious that a comparatively small change in volume can very easily cause the accepted design limitation of ±1 in. of pressure to be exceeded with the consequent danger of destroying the trap seals. The vent piping must be designed to permit the air to flow freely without compression or expansion except for the small amount necessary to overcome friction.

Static Head

γh and h = 144p p = 144 γ

(1)

where p = Pressure, lbf./in2 γ = Specific weight of substance, lbf/ft3 h = Static head, ft

Pneumatic Effects in Sanitary Systems As water flows in contact with air in vertical or horizontal piping, there is friction between the air and water. The frictional effect causes the air to be dragged along with the water and at practically the same velocity as the water. When the cross‑sectional area of the water occupying the pipe is suddenly increased, such as at the hydraulic jump or where a branch discharges into the stack, the air passage is constricted. This constriction acts exactly the same as a stoppage or a blockage to the flow of air. This causes a buildup of pressure, the highest pressure occurring at the constriction and diminishing upstream. It is for this reason that excessive pressure usually develops at the lower floors of a building and at offsets of the stack. It is important to always be aware that protection from the entry of sewer gases is afforded by the 2-in. trap seal, and the design of plumbing systems must be such as to maintain pressure variations within ±1 in. column of water.

Rate of Flow from Outlets The velocity at which air flows out of an outlet to the atmosphere (at the roof terminal of a stack) is due to the total pressure available in the vent pipe at the outlet. This pressure is the flow pressure, which is equal to the static pressure less the pressure lost in friction. The maximum rate of discharge in practice is expressed as: (2) qD = cD q1 where qD = Actual quantity of discharge, gpm q1 = Ideal quantity of discharge, gpm cD = Coefficient of discharge Utilizing the formula q = AV and substituting, (3) qD = cD (2.448 dO2 V1) where dO = Outlet diameter, in. V1 = Ideal velocity, fps Velocity is equal to √2gh, where g = acceleration due to gravity and h = height (or head) of air column. (4)

Static head is the pressure exerted at any point by the weight of the substance above that point. The pressure can be stated in feet of the substance, i.e., when the substance is water the static head is 100 ft of water, or if the substance is air, 100 ft of air. To convert from feet of head to pounds-force per square inch:

qD = cD (2.448 dO2 √2gh) (5) = cD (19.65 dO2 √h) Using 0.67 as an acceptable coefficient of discharge, per Equation 6-1,

Reprinted from Engineered Plumbing Design II, Chapter 8: “Vent Systems,” by A. Calvin Laws, PE, CPD. © American Society of Plumbing Engineers. Plumbing Systems & Design


PSDMAGAZINE.ORG

q = 13.17

h½

pneumatic pressure fluctuations that it is not feasible to prepare

dO D Simpo PDF Merge and Split Unregistered Versiontables - http://www.simpopdf.com of vent sizing for each particular design. Recognizing this, 2

Static Pressure of Air

The design criterion of maintaining pneumatic pressure fluctuations within ± l in. of water column is constantly stressed throughout this book. It should prove interesting to state this pressure in terms of an equivalent column of air. The formula for any substance is, per Equation 1: P = then

γh 144 (6)

P =

γW hW γA hA = 144 144

where γW = Specific weight of water, lbf/ft3 hW = Static head of water, ft γA = Specific weight of air, lbf/ft3 hA = Static head of air, ft

Transposing and using 1 in. of water column, 1 γ h hA = Wγ W = (62.408) ( ⁄12) 0.07512 (at 70° F.) A hA = 69.23 ft of air column A column of air 69.23 ft will exert the same pressure as a column of water 1 in. high. Stated another way, a static head of 1 in. of water will support a column of air 69.23 ft high. The rate of discharge from a vent outlet can now be determined when the pressure at the outlet is 1 in. of water or 69.23 ft of air. qD = 13.17 dO2 h½ = 13.17 dO2 (69.23)½ = (13.17) (8.32) dO2 = 109.57 dO2 The gallons per minute (cubic feet per minute) discharge rate for various diameters of vent pipe at a flow pressure of 1 in. of water column is given in Table 1.

Table 1 Discharge Rates of Air (1 Inch Water Pressure) Outlet Diam, Air Discharge, dO inches qD gpm (cfm) 2 438.3 (58.6) 2½ 684.8 (91.5) 3 986.1 (131.8) 4 1753.0 (234.3) 5 2739.0 (366.1)

Friction Head Loss When air flows in a pipe there is a pressure loss which occurs due to the friction between the air and pipe wall. This loss of pressure can be expressed by the Darcy formula:

authorities base the formulation of venting tables for vent stacks and horizontal branches on the worst conditions that may reasonably be expected. To determine the maximum lengths and minimum diameters for vent stacks it would be valuable to review the conditions of flow in the drainage stack. At maximum design flow, the water flows down the stack as a sheet of water occupying 7∕24 of the cross‑sectional area of the stack. The remaining 17∕24 is occupied by a core of air. As the water falls down the stack, it exerts a frictional drag on the core of air and as this air is dragged down it must be replaced by an equivalent quantity of air so as not to develop negative pressures in excess of -1 in. of water. This is accomplished by extending the soil stack through the roof so that air may enter the stack to replenish the air being pulled down the stack. This is why stacks must be extended full size through the roof and also why soil stacks may not be reduced in size even though the load is less on the upper portions of the stack than it is at the lower portions. Any restriction in the size before terminating at the atmosphere would cause violent pressure fluctuations. As the water flows down the stack and enters the horizontal drain there is a severe restriction to the flow of air as the hydraulic jump occurs. The air is compressed and pressure buildup may become very high. A vent stack is provided in this area of high pressure to relieve the pressure by providing an avenue for the flow of air. Obviously, the vent stack must be large enough to permit the maximum quantity of air dragged down the drainage stack to discharge through it and to the atmosphere without exceeding ±1 in. of water fluctuation The rate of air discharge that must be accommodated for various sizes of drainage stacks flowing at design capacity is tabulated in Table 2. Table 2 Air Required by Attendant Vent Stacks (Drainage Stack Flowing 7∕24 Full) Diameter of Drainage Stack, inches Water Flow, gpm Air Flow, gpm (cfm) 2 23.5 57.1 (7.6) 3 70.0 170.1 (22.7) 4 145.0 352.4 (47.1) 5 270.0 656.1 (87.7) 6 435.0 1057.1 (141.3) 8 920.0 2235.6 (298.9) 10 1650.0 4009.5 (536) 12 2650.0 6439.5 (860.8)

Air Flow in Horizontal Drains (7)

h = f L V D2 g

2

where h = friction head loss, ft. of air column f = coefficient of friction L = length of pipe, ft. D = diameter of pipe, ft. V = velocity of air, ft/sec g = gravitational acceleration 32.2 ft./sec2

Air Flow in Stacks The complete venting of a sanitary drainage system is very complicated as evidenced by the variety of vents employed. There are so many variables that produce positive and negative

It is assumed that the drainage branch flows half full at design conditions and the air in the upper half of the pipe is flowing at the same velocity and capacity. Table 3 tabulates these values for various slopes of drain. Table 3 Rate of Air In Horizontal Drains Diameter of Drain, Slope, Rate of Flow, inches inches per foot gpm (cfm) 1½ ¼ 6.0 (.80) 2 ¼ 8.8 (1.2) 2½ ¼ 15.5 (2.1) 3 ¼ 25.5 (3.4) 1 4 ⁄8 38.0 (5.1) 1 5 ⁄8 69.0 (9.2) 1 6 ⁄8 112.0 (15) 1 8 ⁄8 240.0 (32.1) JANUARY/FEBRUARY 2007


CONTINUING EDUCATION: Vent Systems Permissible Length of Vent Pipe

Figure 1 Various Vent Stack Connections


The maximum length of vent piping, for any particular size with a pressure drop of 1 in. of water, is established by computing the pressure loss for various rates of flow in vents of various diameters. Combining Darcy’s pipe friction formula (Equation 7) and the flow formula, and converting the terms of the equations to units generally used in plumbing: h = f L V D 2g

2

(8)

q = 2.448 d2V (9) q V = 2.448d2 Substituting V in the Darcy equation, f Lq2 h = d ( ⁄12)(64.4)(2.448)2(d)4 Solving for L,

(10)

5 h d5 L = = 22262d 0.013109 f q2 fq

where L = Length of pipe, ft d = Diameter of pipe, in. f = Coefficient of friction q = Quantity rate of flow, gpm

Gravity Circulation The principle of gravity circulation of air is utilized to keep the entire sanitary system free of foul odors and the growth of slime and fungi. The circulation is induced by the difference in head (pressure) between outdoor air and the air in the vent piping. This difference of head is due to the difference in temperature, and thus the difference in density, of each and the height of the air column in the vent piping. The cool air, being more dense, tends to displace the less dense air of the system and circulation of the air is induced. The formula is (11) H = 0.1925 (γO - γ1) HS where H = Natural draft pressure, in. of water γO = Specific weight of outside air, lbf/ft3 γ1 = Specific weight of air in pipe, lbf/ft3 HS = Height of air column or stack, ft Under conditions of natural draft, the rate of flow will be just great enough to overcome losses due to friction.

Vent Stacks Every drainage stack should be extended full size through the roof. The pipe from the topmost drainage branch connection through the roof to atmosphere is called the “vent extension.” The vent extension provides the air that is dragged down the stack and also provides means for the gravity circulation of air throughout the system. Vent extensions may be connected with the vent stack before extending through the roof or may be connected together with other vent extensions or vent stacks in a vent header and the header extended through the roof as a single pipe. Plumbing Systems & Design


Every drainage stack should have an attendant vent stack. The purpose of installing a vent stack is to prevent the development of excessive pressures in the lower regions of the drainage stack by relieving the air as rapidly as it is carried down by the discharge of the drainage stack. The most effective location for the vent stack is below all drainage branch connections and preferably at the top of the horizontal drain immediately adjacent to the stack base fitting. It is at this location that pressure is at its maximum and the danger of closure due to fouling is at its minimum. Figure 1 illustrates acceptable methods of vent stack connections. The vent stack should extend undiminished in size through the roof or connect with the vent extension of the drainage stack at least 6 in. above the overflow of the highest fixture or connect to a vent header.

Vent Terminals Vent terminals should not be located within 10 ft of any door, window, or ventilation intake unless they are extended at least 2 ft above such openings. Terminals should be at least 6 in. above roof level and at least 5 ft above when the roof is used for other PSDMAGAZINE.ORG

purposes. When it is impractical to extend the vent through the Some of the conclusions drawn by French and Eaton as a result Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com roof, it is permissible to terminate through a wall, but the ter- of their investigations are very illuminating and are quoted minal must turn down and be covered with a wire screen. The herewith: terminal should never be located beneath a building overhang. 1. Increasing the diameter of the outlet orifice of a lavatory

Fixture Trap Vents

The water seal of all fixture traps should be protected against siphonage or blowout by the proper installation of a venting system. When drainage stacks are provided with an adequate supply of air at the terminal and an adequate vent stack is provided to relieve excess pressures at the base of the drainage stack, the only additional vent protection required to prevent water seal loss in fixture traps is that necessary to prevent self‑siphonage when the fixture discharges and to relieve excessive pneumatic effects in the branch drains when other fixtures discharge into the branch. Some municipalities require that every fixture trap be individually vented, but most localities permit alternate methods such as 1. 2. 3. 4.

Wet venting Stack venting Circuit and loop venting Combination waste and vent venting

Distance of Vent from Trap The most comprehensive investigations of conditions under which fixture traps will be safe from self‑siphonage have been conducted by the National Bureau of Standards in the United States and by the Building Research Station in England. The recommended maximum distances of a vent from the weir of the trap to the vent connection are tabulated in Table 4. As illustrated in Figure 2, the vent pipe opening, except for water closets and similar fixtures, must never be below the weir of the fixture trap. A fixture drain that slopes Table 4 Distance of Vent from Fixture Traps Maximum Distance more than one pipe diamof Vent to Trap Size of Fixture Drain eter between vent opening inches inches and trap weir has a greater 1¼ 30 tendency to self‑siphon 1½ 42 the trap seal than a fixture 2 60 drain installed at a slope 3 72 of not more than one pipe 4 120 diameter. Self‑Siphonage of Fixture Traps, National Bureau of Standards Building Materials and Structures Report BMS 126 (1951), prepared by John L. French and Herbert N. Eaton, is a very thorough study of self‑siphonage Figure 2 Vent Pipe Opening

from 11⁄8 in. to 1¼ in. increases the trap seal loss greatly, frequently more than 100%, owing to the increased discharge rate. 2. Flat‑bottomed fixtures cause smaller trap seal losses than do round fixtures, owing to the greater trail discharge from the former. 3. With a 1½-in. fixture trap and drain, an 1in. by 20-in. lavatory gave greater trap‑seal losses than did a 20-in. by 24-in. lavatory, presumably owing to the greater trail discharge of the latter. When a 1¼ in. trap and drain were used, no particular difference was noted in the trap seal losses caused by the two lavatories. 4. The elimination of the overflow in lavatories will increase the trap seal losses substantially. 5. The effect on trap seal losses of varying the vertical distance from the fixture to the trap from 6 in. to 12 in. appears to be negligible. 6. For a given rate of discharge from a lavatory, decreasing the diameter of the drain will increase trap seal losses. 7. An increase in slope or a decrease in diameter of the fixture drain will tend to cause increased losses due to self‑siphonage, and these two dimensions are fully as important as the length of fixture drain in causing self‑siphonage. 8. Trap seal losses are usually much greater when a long‑turn stack fitting is used than when a short‑turn or straight‑tee fitting is used. No significant difference between the behavior of short‑turn and straight‑tee fittings was observed. Thus, since it is known that a long‑turn fitting is more effective in introducing water from a horizontal branch into the stack than is either the short‑turn or straight‑tee fitting, the characteristics of these fittings are contradictory in these respects. The fitting that is most advantageous from the standpoint of introducing the water into the stack is the least advantageous from the standpoint of self‑siphonage. 9. Trap seal losses are increased if the internal diameter of a P‑trap is less than that of the fixture drain. Thus, if we are to prevent excessive trap seal losses for a P‑trap due to self‑siphonage, we should use a trap having a fairly large internal diameter. Furthermore, siphonage of the trap due to pressure reductions caused by the discharge of other fixtures on the system can be rendered less harmful by using a trap with a large depth of seal. While increasing the depth of seal may lead to greater trap seal losses, it also results in a greater remaining trap seal than if a trap with a shallow seal were used. 10. The test results on the self‑siphonage of water closets have indicated that the unvented length of drain for these fixtures need not be limited because of self‑siphonage. 11. Standardization of the dimensions of fixture traps and especially of lavatory traps, with regard to internal diameter and depth of trap seal is highly desirable. Minor restrictions on these dimensions can lead to substantially increased lengths of fixture drains. JANUARY/FEBRUARY 2007


CONTINUING EDUCATION: Vent Systems 12. Standardization of the hydraulic characteristics of fixtures is Figure 5 Venting for Stacks Having More Than 10 Branch Intervals Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com desirable, at least for lavatories, sinks, and combination fixtures. Substantially increased permissible unvented lengths of fixture drains can be obtained for a moderate decrease in the discharge rates of the fixtures. 13. Increase in depth of trap seal above the 2-in. minimum commonly permitted by codes will make it possible to increase appreciably the maximum permissible unvented lengths of fixture drains. These conclusions clearly illustrate various approaches in the effort to make plumbing systems less costly without affecting efficiency. The proper design of fixtures and fixture drain lines and limiting the maximum discharge rates of faucet‑controlled fixtures could result in longer unvented lengths of drains.

Various Methods of Fixture Trap Venting Figure 3 illustrates various fixture trap vents and their proper nomenclature. When venting one trap the vent is called an “individual” or “back vent.” If fixtures are back to back or side by side and one vent is used for the two traps, the vent is a “common vent.” Any connection from the vent stack is a “branch vent.” All vent piping should be graded to drain back to the drainage piping by gravity. The vent should be taken off above the centerline of the drainpipe and rise vertically or at an angle of not Figure 3 Various Fixture Trap Vents

more than 45° from the vertical. The horizontal run of the vent should be at least 6 in. above the overflow level of the fixture. (See Figure 4.)

Relief Vents

Figure 4 Horizontal Run of Vent


Pressures in the drainage and vent stacks of a multistory building are constantly fluctuating. The vent stack connection at the base of the drainage stack and the branch vent connections to the branch drains cannot always eliminate these fluctuations. It then becomes extremely important to balance pressures throughout the drainage stack by means of “relief vents” located at various intervals. The fluctuations in pressure may be caused by the simultaneous discharge of branches on various separated floors. Drainage stacks in buildings having more than ten branch intervals should be provided with a relief vent at each tenth interval, counting from the topmost branch downward. The lower end of the relief vent should connect to the drainage stack below the drainage branch connection and the upper end should connect to the vent stack at least 3 ft above the floor level. (See Figure 5.) Relief vents are required where a drainage stack offsets at an angle of more than 45° to the vertical. Such offsets are subject to high pneumatic pressure increases and extreme surging flow JANUARY/FEBRUARY 2007

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Figure 6 Venting at Stack Offsets

Figure 7 Wet Venting at Top Floor


Figure 8 Wet Venting Below Top Floor

connection level or below. (See Figure 7.)

conditions. The methods of installing relief vents are illustrated in Figure 6.

Continuous Venting

At lower floors: The rules are the same except that the water closets must be vented and the wet vent must be 2 in. minimum. Water closets below the top story need not be individually vented if a 2-in. wet vented waste pipe connects directly to the upper half of the horizontal water closet drain at an angle no greater than 45° from the angle of flow. (See Figure 8.)

A system of individual or common vents for every trap is called “continuous venting.” Every fixture trap is provided with a vent. It is the most expensive system but provides positive protection of all trap seals.

“Stack venting” finds its general application in one‑family homes and the top floor of multistory buildings. (See Figures 7 and 9.)

Wet Venting A “wet vent” is a vent that vents a particular fixture and at the same time serves as a waste to receive the discharge from other fixtures. The objective of using wet vents is to minimize the vent piping required by employing one pipe to serve two functions. There are three fundamental rules to follow when utilizing a wet vent:

“Combination waste and vent venting” is used primarily for venting floor drains and laboratory and work tables. The drainage piping is oversized at least two sizes larger than required for draining purposes only and the drainage branch and stack should be provided with vent piping. This type of venting is employed when it is impractical to employ the other methods.

At top floor: 1. No more than 1 FU is discharged into a 1½-in. wet vent nor more than 4 FU into a 2-in. wet vent. 2. Length of drain does not exceed maximum permissible distance between trap and vent. 3. Branch connects to the stack at the water closet

Combination Waste and Vent Venting

Circuit and Loop Venting There has developed a tendency to call all “circuit venting” by the name applicable to a special installation of circuit venting. A circuit vent is a branch vent that serves two or more floor outlet fixtures, except blowout water closets, and extends from in front of the last fixture connection on the horizontal drain to the vent stack. A “loop vent” is the same, except that it is employed on the topmost floor serving fixtures and is connected to the vent JANUARY/FEBRUARY 2007


CONTINUING EDUCATION: Vent Systems in the sanitary system by the presence of suds. (An interesting

Figure 9 Stack Vented Unit

Simpo PDF Merge and Split Unregistered Versionsidelight - http://www.simpopdf.com is that suds, in and of themselves, do not enhance the

extension of the drainage stack instead of to the vent stack. (See Figure 10.) When wall outlet fixtures are connected to the branch drain serving the floor outlet fixtures, the former must be provided with individual vents that can connect to the circuit vent or loop vent.

Common Vents Where two fixtures are connected to a vertical branch at the same level, a “common vent” may be employed. When one of the fixtures connects at a different level than the other, observe the following procedure. If fixture drains are the same size, increase the vertical drain one size. If fixture drains are of different sizes, connect the smaller above the larger connection and maintain the vertical size up to the top connection.

Suds Pressure The prevalent use of high‑sudsing detergents in washing machines, dishwashers, laundry trays, and kitchen sinks has created serious problems in all residential buildings and especially in high‑rise buildings. Until manufacturers are forced to market only detergents without sudsing characteristics, the plumbing engineer must understand and cope with the dangers created Figure 10 Circuit and Loop Venting

cleaning ability of soaps or detergents in any way.) When the flow of wastes from upper floors contains detergents, the sudsingredients are vigorously mixed with the water and air in the stack as the waste flows down the stack and further mixing action occurs as other branch waste discharges meet this flow. These suds flow down the stack and settle in the lower sections drainage system and at any offsets greater than 45 degrees in the stack. Investigation has shown that when sudsing wastes are present, the sanitary and vent stacks are laden with suds and this condition was found to exist for extended periods of time. Liquid wastes are heavier than suds and easily flow through the suds‑loaded drainage piping without carrying the suds along with the flow. Everyone is aware of the difficulty of flushing the suds out of a sink. The water simply flows through the suds and out the drain, leaving the major portion of the suds behind. The same action occurs in the lower sections of the drainage system except for one important difference—air, as well as water, is now flowing in the piping. This air, which is carried down with the waste discharge, compresses the suds and forces them to move through any available path of relief. The relief path may be the building drain, any branches connected to the building drain, the vent stack, branch vents, individual vents or combinations of the foregoing. A path of relief may not always be available or could be cut off or restricted by the hydraulic jump, or a path may just be inadequate because of location or size. If one or more of these conditions exist, excessively high suds pressure can develop and blow the seals of traps with the accompanying appearance of suds in fixtures. High suds pressure zones occur at every change in direction, vertically or horizontally, that is greater than 45°. Where vent stack base connections, relief vents, branch vents, or individual vents serve as the relief path for the high suds pressure, they are usually found to be inadequate in size with resultant suds conditions appearing at the fixtures. The vent pipe sizing tables in practically every code are calculated on the basis of air flow capacity and do not in any way provide for the more demanding flow of suds. Sizes that are based on these code tables are inadequate to accommodate suds flow and thus are incapable of providing adequate suds pressure relief. Suds are much heavier than air and consequently do not flow with the same ease. They produce a much greater friction head loss for the same rate of flow. The density of old or regenerated suds varies from 2 lb/ft3 to a high of 19 lb/ft3, depending upon the detergent used. For equal rates of flow and pressure loss, the vent pipe diameter for suds relief flow must be from 20 to 80% greater than for air flow. Whenever a soil or waste stack receives washing machines, dishwashers, laundry trays, kitchen sinks, or other fixtures where sudsing detergents are used, the drainage and vent piping for the lower-floor fixtures or for the fixtures above offsets must be arranged to avoid connection to any zone where suds pressure exists. Suds pressure zones exist in the following areas: 1. At a soil or waste stack offset greater than 45°: 40 stack diameters upward and 10 stack diameters horizontally from the base fitting for the



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Figure 11 Suds Pressure Zones

water‑supplied receptacle. The stack should extend through

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com the roof.

An individual vapor vent drip can be connected through an air gap to the inlet of the trap serving the fixture. Vapor vents for bedpan washers and bedpan sterilizers must not connect with the vapor vents of other fixtures. Sizing of the vapor vent stack may be by empirical methods or the rational approach may be used. The minimum size of the stack should be 1¼ in.

Ejector and Sump Vents Ejectors, other than the pneumatic type, operate at atmospheric pressure and receive drainage discharge under gravity flow conditions. An ejector is installed when the level of fixture discharge is below the level of the public sewer. It is convenient to view an ejector system as being exactly similar to the gravity sanitary system and all of the requirements for the proper design of the sanitary system are applicable. Thus, the air required to be conveyed by the vent piping is the same as the maximum rate at which sewage enters or is pumped out of the receiver. The ejector vent can be determined by reference to Equation 10: L = 2226

( fqd ) 2 2

and using Table 1, which gives air discharge in gpm for various pipe diameters. It has been found in practice that 3 in. is adequate except for extremely large installations.

Frost Closure upper stack section. A pressure zone also exists 40 stack diameters upstream from the top fitting of the lower stack section. 2. At the base of a soil or waste stack: The suds pressure zone extends 40 stack diameters upward from the base fitting. 3. In the horizontal drain from the base of a stack: The suds pressure zone extends 10 stack diameters from the base fitting, and where an offset greater than 45° in the horizontal occurs, the pressure zones extend 40 stack diameters upstream and 10 diameters downstream from the offset fitting. 4. In a vent stack connected to a suds pressure zone: The suds pressure zone exists from the vent stack base connection upward to the level of the suds pressure zone in the soil or waste stack. Figure 11 illustrates all the above zones.

Vapor Vents (Local Vents) Years ago water closets and urinals were equipped with connections for venting the fixture to the outdoors to eliminate foul odors. Fixture design has been improved so that these vents are no longer required. The use of “vapor vents” is now applied to sterilizing equipment and bedpan washers. This application is also rapidly disappearing as new methods of condensing the foul vapors are being built into the equipment. When a vapor vent is used, it must be isolated from the sanitary venting system. The base of a vapor vent stack should terminate in a trap, to prevent the escape of vapors, and spill to a trapped, vented, and

Where the danger of frost closure of vent terminals is present, the minimum size of the vent stack or vent extension through the roof should be 3 in. When a vent stack must be increased in size going through the roof, the increase should be made inside the building at least 1 ft below the roof. The National Bureau of Standards has investigated the problem of frost closure both theoretically and experimentally. It was demonstrated that a 3-in. vent terminal froze up solidly at -30°F only over an extended period of time. Closure occurs at the rate of 1½ in. for every 24 hr. that the temperature remains at -30°F. It can be seen that frost closure presents a real problem only in the far northern regions. The problem is serious in Canada, and they have devised various methods of overcoming it: 1. Vent terminal to extend only 1 in. or 2 in. above the roof. The more pipe exposed to the atmosphere, the greater the problem. Snow covering the vent terminal has proven to cause no trouble. The snow is porous enough for the passage of air and melts rather rapidly at the outlet. 2. Enlargement of the stack below the roof. The increased diameter decreases the chance of complete closure and the stream of air tends to flow through the enlarged portion without touching the walls of the enlarged pipe. 3. Install cap flashing at the terminal and counterflashing to leave an air space from the heated building. Frost closure depends upon the: (1) outside temperature, (2) temperature and humidity of inside air, (3) wind velocity, (4) length of exposed pipe, (5) diameter of exposed pipe, and (6) velocity of air flow. There is very little danger of frost closure unless the outside temperature falls below -10°F and remains JANUARY/FEBRUARY 2007


CONTINUING EDUCATION: Vent Systems there for several days. It has been found that if frost closure does Simpo PDF Merge and Split Unregistered Version occur, siphonage of traps is reduced or prevented by connecting the drainage and vent stacks together before extending through the roof. An analysis of air flow under these conditions will convince the plumbing engineer of its validity, as it can be seen that air forced into the vent stack at its base will be introduced into the soil stack at the top connection.


Tests of Plumbing Systems The complete storm and sanitary system should be subjected to a water test and proven watertight upon completion of the rough piping installation and prior to covering or concealment. The test pressure should be a minimum of a 10‑ft column of water except for the topmost 10 ft of pipe. The test pressure should never exceed a maximum of a 100‑ft column of water. Any greater pressure will cause the test plugs used to seal temporarily open piping in the system to blow. If the system is higher than 100 ft, test tees may be installed at appropriate heights so as to test the building in sections. Very rarely in practice are more than seven stories tested at one time. If it is not possible to perform a water test, an air test is acceptable. The air test shall be made by attaching an air compressor testing apparatus to any suitable opening, and, after closing all other inlets and outlets to the system, forcing air into the system until there is a uniform gage pressure of 5 psi (34.5 kPa) or a pressure sufficient to balance a column of mercury 10 in. (254 mm) in height. The pressure shall be held without introduction of additional air for a period of at least 15 min. Upon completion of the sanitary system and after all fixtures are installed with traps filled with water, the system should be subjected to an additional test and proved gastight. An alternate test is the smoke test. The smoke test is performed by introducing pungent, thick smoke produced by smoke bombs or smoke machines. When smoke appears at the roof terminals, each terminal is sealed and a smoke pressure of 1‑in. column of water is maintained to prove the system gastight. This test is not practical and is seldom used. Another alternate test is the peppermint vapor test. At least 2 oz. of oil of peppermint are introduced into each roof terminal and vaporized by immediately pouring 10 qt of boiling water down the stack. The terminals are promptly sealed. Oil of peppermint and any person coming in contact or handling the oil must be excluded from the interior of the building for the duration of the test. Leakages will be detected by the peppermint odor at the source. However, it is very difficult to pinpoint the leak by this method. This test is not practical and is seldom used. ✺



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The technical article you must read to complete the exam is located at www.psdmagazine.org. The following exam and application form also may be downloaded from the Web site. Reading the article and completing the form will allow you to apply to ASPE for CEU credit. For most people, this process will require approximately one hour. If you earn a grade of 90 percent or higher on the test, you will be notified that you have logged 0.1 CEU, which can be applied toward the CPD renewal requirement or numerous regulatory-agency CE programs. (Please note that it is your responsibility to determine the acceptance policy of a particular agency.) CEU information will be kept on file at the ASPE office for three years. Note: In determining your answers to the CE questions, use only the material presented in the corresponding continuing education article. Using information from other materials may result in a wrong answer.

CE Questions—“Vent Systems” (PSD 137) 1. A wet vent is ___________. a. not allowed by most codes b. a vent that vents a particular fixture and at the same time serves as a waste vent to receive the discharge from other fixtures c. not allowed to serve water closets d. a system of individual or common vents for every trap 2. The vent piping must be designed to permit the air to ___________. a. flow freely b. enter the piping network c. exit the piping network d. be compressed 3. Suds, in and of themselves, ___________. a. do not enhance the cleaning ability of soaps or detergents in any way b. are only a problem if they are allowed to accumulate in large numbers c. require wet venting to rinse the suds out of the drain pipe d. none of the above 4. The most expensive venting system is a ___________ system. a. wet vent, b. continuous vent, c. circuit vent, d. loop vent 5. Vapor vents ___________. a. must be isolated from the sanitary venting system b. may be connected through an air gap to the trap serving the fixture c. must not be connected to the vapor vents of other types of equipment d. all of the above 6. To compensate for suds density, the vent pipe for suds relief flow must ___________. a. not be depended on for suds protection b. connect to each fixture trap 12 Plumbing Systems & Design


About This Issue’s Article The January/February 2007 continuing education article is “Vent Systems,” Chapter 8 of Engineered Plumbing Design II by A. Calvin Laws, PE, CPD. Flow of air is the primary consideration in the design of a venting system for the ventilation of the piping and protection of the fixture trap seals of a sanitary drainage system. Since air is of such primary importance, it is essential that the plumbing engineer be familiar with certain physical characteristics that are pertinent to its behavior in a plumbing system. This chapter explains these fundamentals that are vital to the design of a vent system. It also covers vent stacks, the various types of vents and venting, the effects of suds pressure, frost closure, and vent system pressure tests. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

PSD 137


c. connect 10 pipe diameters from any high pressure suds zone d. be 20 percent to 80 percent larger in diameter 7. What is the primary consideration in the design of a venting system? a. removing odors from the sewer system b. correctly sizing the vent piping to match the size of the waste piping c. the flow of air in the vent system d. none of the above

8. For a given rate of discharge from a lavatory, decreasing the diameter of the drain will ___________. a. increase the water discharge velocity from the fixture b. decrease the water discharge velocity from the fixture c. increase trap seal losses d. prevent trap seal losses 9. Smoke tests and peppermint air tests ___________. a. can detect the location of a leak in a vent system b. are no longer allowed by OSHA and the EPA c. are not practical and seldom used d. may not be used where frost closure is expected

10. A column of air 69.23 feet high exerts the same pressure as a column of water ___________ high. a. 1 inch, b. 10 inches, c. 100 inches, d. 1,000 inches 11. A branch vent interval is ___________. a. determined by the floor-to-floor height of the building b. dependent on the arrangement of the fittings connecting at each floor c. at least 8 feet between branches d. of no importance in modern plumbing systems 12. The maximum distance of a vent to a 2-inch-diameter trap is ___________. a. 30 inches, b. 42 inches, c. 60 inches, d. 72 inches

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Vent Systems (PSD 137)



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Vent Systems (PSD 137) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________



Water System Design

PSD 138



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Water System Design


The objective in designing the water supply systems for any project is to ensure an adequate water supply at adequate pressure to all fixtures and equipment at all times and to achieve the most economical sizing of the piping. There are at least six important reasons that proper design of water distribution systems is absolutely essential: 1. Health. This is of irrefutable and paramount importance. Inadequate or improper sizing can cause decreases in pressure in portions of the piping system, which in turn can cause contamination of the potable water supply by backflow or siphonage. There are too many well-documented deaths attributable to this cause. 2. Pressure. It is essential to maintain the required flow pressures at fixtures and equipment or improper operation will result. 3. Flow. Proper and adequate quantities of flow must be maintained at fixtures and equipment for obvious reasons. 4. Water Supply. Improper sizing can cause failure of the water supply due to corrosion or scale buildup. 5. Pipe Failure. Pipe failure can occur due to the relation of the rate of corrosion with excessive velocities. 6. Noise. Velocities in excess of 10 ft/sec will cause noise and increase the danger of hydraulic shock. Of all the complaints resulting from improperly designed water systems, the two that occur most frequently are (1) lack of adequate pressure and (2) noise. Noise may not be detrimental to the operation of a water distribution system but it is very definitely a major nuisance. The lack of adequate pressure, however, can have very serious repercussions in the operation of any water system.

Flow Pressure

reading the gauge while flow is occurring. With the flow pressure known, the following formula can be used: (1)

q = 20d2 p½

where q = rate of flow at the outlet, gpm d = actual inside diameter (ID) of outlet, in. p = flow pressure, psi Assume a faucet with a 3⁄8-in. supply and the flow pressure is 16 psi. Then: q = 20 × (3⁄8)2 × (16)½ = 20 × 9⁄64 × 4 = 11.25 gpm The flow for a ¼-in. and 1⁄8-in. supply at the same pressure would be 5 gpm and 1.25 gpm, respectively.

Constant Flow Pressures in the various parts of the piping system are constantly fluctuating depending upon the quantity of flow at any moment. Under these conditions the rate of flow from any one outlet will vary with the change of pressure. In industrial and laboratory projects there is some equipment that must be supplied with a fixed and steady quantity of flow regardless of line pressure fluctuations. This feature is also desirable in any type of installation. This criterion can easily be achieved by the utilization of an automatic flow-control orifice. A flow control is a simple, selfcleaning device designed to deliver a constant volume of water over a wide range of inlet pressures. (See Figures 1 and 2.) The automatic controlling mechanism consists of a flexible orifice that varies its cross-sectional area inversely with the pressure so that a constant flow rate is maintained under all conditions. Until the inlet pressure reaches the threshold pressure (12–15 psi), the flexible insert acts as a fixed orifice. When the threshold pressure is exceeded, the cross-sectional area of the orifice is decreased by the flexure of the insert. This causes a pressure drop that is equal to whatever pressure is necessary to absorb the energy not required to overcome system friction and to

It is essential that the term flow pressure be thoroughly understood and not confused with static pressure. Flow pressure is that pressure that exists at any point in the system when water is flowing at that point. It is always less than the static pressure. To have flow, some of the potential energy is converted to kinetic energy and additional energy is used in overcoming friction, which results in a flow pressure that is less than the static pressure. Figure 1 Flow Control When a manufacturer lists the minimum pressure required for the proper operation of a flush valve as 25 psi, it is the flow pressure requirement that is being indicated. The flush valve will not function at peak efficiency (if at all) if the engineer has erroneously designed the system so that a static pressure of 25 psi exists at the inlet to the flush valve.

Flow at an Outlet There are many times when the engineer must determine how many gallons per minute are being delivered at an outlet. This can easily be determined by installing a pressure gauge in the line adjacent to the outlet and

Reprinted from Engineered Plumbing Design II, Chapter 13: “Water System Design,” by A. Calvin Laws, PE, CPD. © American Society of Plumbing Engineers. Plumbing Systems & Design

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Figure 2 Flow Control Device Curve (Dole Valve)

these problems because they automatically com-

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com pensate for changes in the line pressure to hold the

rate of water delivery from all outlets to a preselected number of gallons per minute. One very important word of caution—a flow control is not designed to perform the function of pressure regulation and should never be used where a pressure-regulating valve is required.

Material Selection Before the type of material for the piping of a water distribution system can be selected, certain factors must be evaluated:

Table 1 Actual Inside Diameter of Piping,in Inches Nominal Iron or Steel Brass or Copper Water Copper Water Pipe Size, Pipe, Sch. Copper Pipe Tube, Type K Tube, Type L In. 40 ½ 0.622 0.625 0.527 0.545 ¾ 0.824 0.822 0.745 0.785 1 1.049 1.062 0.995 1.025 1¼ 1.380 1.368 1.245 1.265 1½ 1.610 1.600 1.481 1.505 2 2.067 2.062 1.959 1.985 2½ 2.469 2.500 2.435 2.465 3 3.068 3.062 2.907 2.945 4 4.026 4.000 3.857 3.905 5 5.047 5.062 4.805 4.875 6 6.065 6.125 5.741 5.845 8 7.981 8.001 7.583 7.725 10 10.020 10.020 9.449 9.625

1. The characteristics of the water supply must be known. What is the degree of alkalinity or acidity? A pH above 7 is alkaline and below 7 is acidic. A pH of 7 represents neutral water. What is the air, carbon dioxide, and mineral content? The municipal water supply department can usually furnish all this information. If it is not available, a water analysis should be made by a qualified laboratory. 2. What are the relative costs of the various suitable materials? 3. Ease of replacement—can the material be obtained in a reasonable time or must it be shipped from localities that might delay arrival for months? 4. Actual inside dimensions of the same nominal size of various materials differ. This variation in ID can have a significant effect on sizing because of the variation in quantity rates of flow for the same design velocity. Table 1 shows the actual ID for various materials. 5. The roughness or smoothness (coefficient of friction) of the pipe will have a marked effect on pipe sizes.

Parallel Circuits There are many parallel pipe circuits in the water distribution system of any job. An arrangement of parallel pipe circuits is one in which flow from a single branch divides and flows in two or more branches which again join in a single pipe. Figure 3 illustrates a simple two-circuit system. The total flow entering point A is the same leaving point A with a portion flowing through branch 1 and the rest through branch 2. Flows q1 and q2 must equal q and the total pressure drop from A to B is the same

sustain the rated flow. The curve shown in Figure 2 is typical of most flow controls regardless of the rated flow, which is why no figures are shown for the gallons per minute axis. It is possible to approximate the flow of a specific flow control by using the line marked “Nominal Flow Rate” as the desired rate. Assume a piece of equipment requires the fixed Figure 3 Typical Parallel Pipe Circuit flow of 40 gpm and there is considerable line pressure fluctuation. A flow control would be specified to deliver 40 gpm. By use of the curve in Figure 2 the deviation from 40 gpm at various pressures can be read by assigning a value of 40 to the nominal flow rate line on the vertical scale and zero to the baseline. Standard flow controls are available in sizes from ¼ in. to 2½ in. and flow rates from ¼ to 90 gpm. They are ideal for use in limiting the maximum rate of flow to any fixture. It is not unusual in a water distribution system to experience fluctuating discharges at fixtures and equipment due to other fixtures and equipment starting up or shutting down. Flow controls will minimize

MARCH/APRIL 2007


CONTINUING EDUCATION: Water System Design makeup water, which usually cause excessive pres-

Figure 4 Example of Division of Flow in a Parallel Pipe Circuit

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com sure loss in the mains. Future growth of the area must also be analyzed. If large housing, commercial, or industrial development is anticipated, the pressure available will certainly decrease as these loads are added to the public mains. It is good practice to assume a pressure available for design purposes as 10 psi less than the utility quotes. If the pressure from the public mains is inadequate for building operation, other means must be provided for increasing the pressure to an adequate level. There are three basic methods available: 1. Gravity tank system 2. Hydropneumatic tank system 3. Booster pump system

whichever branch is traversed. The rate of flow through each branch becomes such as to produce this equal pressure drop. The division of flow in each branch can then be expressed as: (2)

q1 = q2

d ( Ö d) L2 L1

1

5

2

Assume there is a flow in a 3–in. pipe of 160 gpm entering point A and leaving point B as shown in Figure 4. The length of branch 1 is 20 ft and branch 2 is 100 ft. The size of branch 1 is 2 in. and branch 2 is 3 in. To determine the quantity of flow in each branch, the basic formula is applied, and: q1 100 2 5 q2 = 20 3

Ö

since q1 + q2 = 160

( )

= Ö5 (.66)5 = Ö5 × 0.125 = 0.79 q1 = 0.79q2

then 0.79q2 + q2 = 160 1.79q2 = 160 q2 = 89.4 gpm and q1 = 160 - 89.4 = 70.6 gpm or q1 = 0.79 × 89.4 = 70.6 gpm

Inadequate Pressure As previously noted, lack of adequate pressure is one of the most frequent complaints and could be the cause of serious troubles. The pressure available for water distribution within a building can come from various sources. Municipalities usually maintain water pressure in their distribution mains within the range of 35–45 psi. There are localities where the pressure maintained is much less or greater. The local utility will furnish the information as to their minimum and maximum operating pressures. When utilizing only the public water main pressure for the water distribution system within a building, it is very important to determine the pressure available in the mains during the summer months. Huge quantities of water are used during this period for sprinkling of lawns and for air-conditioning cooling tower Plumbing Systems & Design

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Each system has its own distinct and special advantages and disadvantages. All three should be evaluated in terms of capital expenditure, operating costs, maintenance costs, and space requirements. Depending upon which criteria are the most important, this will dictate which system is selected.

Flow Definitions Maximum flow or maximum possible flow is the flow that will occur if the outlets on all fixtures are opened simultaneously. Average flow is that flow likely to occur in the piping under normal conditions. Maximum probable flow is the maximum flow that will occur in the piping under peak conditions. It is also called peak demand or peak flow.

Demand Types Some outlets impose what is called a continuous demand on the system. They are differentiated from outlets that impose an intermittent demand. Outlets such as hose bibbs, lawn irrigation, air-conditioning makeup, water cooling, and similar flow requirements are considered to be continuous demands. They occur over an extended period of time. Plumbing fixtures draw water for a relatively short period of time and are considered as imposing an intermittent demand. Each fixture has its own singular loading effect on the system, which is determined by the rate of water supply required, the duration of each use, and the frequency of use. The water demand is related to the number of fixtures, type of fixtures, and probable simultaneous use.

Estimating Demand The basic requirements for estimating demand call for a method that 1. Produces estimates that are greater than the average demand for all fixtures or inadequate supply will result during periods of peak demand. 2. Produces an accurate estimate of the peak demand to avoid oversizing. 3. Produces estimates for demand of groups of the same type of fixtures as well as for mixed fixture types. Design Loads Arriving at a reasonably accurate estimate of the maximum probable demand is complicated due to the intermittent operation and irregular frequency of use of fixtures. Different kinds of fixtures are not in uniform use. Bathroom fixtures are most frequently used on arising or retiring and, not surprisingly, during television commercials. Kitchen sinks find heavy usage PSDMAGAZINE.ORG

before and after meals. Laundry trays and washing machines Water Supply Fixture Units Simpo PDF and Split Unregistered VersionA-standard http://www.simpopdf.com are most likely to beMerge used in the late morning. During the period method for estimating the water demand for a buildfrom midnight to 6 P.M. there is very little fixture use. Luckily, ing has evolved through the years and has been accepted almost fixtures are used intermittently and the total time in operation is unanimously by plumbing designers. It is a system based on relatively small so it is not necessary to design for the maximum weighting fixtures in accordance with their water supply loadpotential load. Maximum flow is therefore of no real interest to producing effects on the water distribution system. The National the designer. Average flow is also of no concern, for if a system Bureau of Standards has published report BMS 65, Methods of were designed to meet this criterion it would not satisfy the con- Estimating Loads in Plumbing Systems, by the late Dr. Roy B. ditions under peak flow. It is therefore necessary to consider Hunter, which gives tables of load-producing characteristics only the maximum probable demand (peak demand) imposed (fixture unit weights) of commonly used fixtures, along with by the fixtures on a system. probability curves that make it possible to apply the method Two methods have evolved in the United States that, when easily to actual design problems. used where applicable, have proven to give satisfactory results. The method of probability should not be used for a small They are the empirical method and method of probability. The number of fixtures. Although the design load, as computed by empirical method is based upon arbitrary decisions arrived at this method, has a certain probability of not being exceeded, from experience and judgment. It is useful only for small groups it may nevertheless be exceeded on rare occasions. When a of fixtures. The method of probability is based upon the theory system contains only a few fixtures, the additional load imposed of probabilities and is most accurate for large groups of fixtures. by one fixture more than has been calculated by the theory of In the past, certain demand rates became generally accepted probability can easily overload the system. When a system conas standard. These rates are tabulated in Table 2 for the common tains a large number of fixtures, one or several additional fixture types of fixtures and the average pressure necessary to deliver loadings will have an insignificant effect on the system. this rate of flow. The actual pressure for a specific fixture will In developing the application of the theory of probability to vary with each manufacturer’s design, some requiring a greater determine design loads on a domestic water distribution system, or lesser pressure than others. Hunter assumed that the operation of the fixtures in a plumbAlthough the flow rates shown in Table 2 have been used by ing system could be viewed as purely random events. He then engineers, they are hopelessly outdated. Water conservation determined the maximum frequencies of use of the fixtures. He measures being mandated by federal regulations and model obtained the values of the frequencies from records collected codes make the flow rates shown in Table 2 unreasonable for in hotels and apartment houses during the periods of heaviest use in the design of systems. The federal Energy Policy Act usage. He also determined characteristic values of the average (EPACT92) established the following criteria for water use by rates of flow for different fixtures and the time span of a single fixture: operation of each. If only one type of fixture were used in a building, the appli Water closets: 1.6 gal/flush cation of the theory of probability would be very simple and Urinals: 1.5 gal/flush straightforward. When dealing with systems composed of Showers: 2.5 gpm various types of fixtures that must be combined, the process Lavatories: 2.5 gpm becomes extremely involved and too complicated to be of any Sinks: 2.5 gpm Manufacturers offer fixtures meeting these and more stringent practical use. Faced with this dilemma, Hunter devised an ingerequirements. Lavatories with 0.5 gpm flow rates and urinals nious method to circumvent the problem by a simple process with 1.0 gal/flush have been installed in thousands of buildings which yields results within ½% accuracy of the more involved with satisfactory results. However, there is a need for research and laborious calculations required. He conceived the idea of to determine the actual minimum flow required, for each type assigning “fixture loading factors” or “fixture unit weights” to of fixture, to satisfy psychological requirements of the user and the different kinds of fixtures to represent the degree to which they loaded a system when used at their maximum assumed provide the necessary sanitary requirements. frequency. A fixture unit weight of 10 was arbitrarily assigned by Hunter to a flush valve, and all other fixtures were assigned values based on their load-producing effect in relation to the flush valve. All fixtures have been converted, in essence, to one fixture type and the application of the theory of probability is Table 2 Demand at Individual Fixtures and Required greatly simplified. Pressure Hunter assigned water supply fixture unit (FU) values for difFixture Flow Pressure, Flow Rate, ferent kinds of fixtures, which are given in Table 3. Conversion psi gpm of fixture unit values to equivalent gallons per minute, based on Ordinary lavatory faucet 8 3.0 the theory of probability of usage developed by Hunter, is given Self-closing lavatory faucet 12 2.5 in Table 4. A graphic representation of this table is shown by Sink faucet, 3∕8 in. 10 4.5 Sink faucet, ½ in. 5 4.5 Figures 5 and 6 (Hunter’s Curve). Figure 7 gives a graphic repBathtub faucet 5 6.0 resentation of the conversion from fixture units to gallons per Laundry tub faucet, ½ in. 5 5.0 minute for a mixed system. An examination of the curves and Shower head 12 5.0 tables reveals that demand for a system utilizing flush valves is Water closet flush tank 15 3.0 much greater than that for flush tanks for small quantities. The Water closet flush valve, 1 in. 10–25 15–45 difference in demand for each system decreases as the fixture Urinal flush valve, ¾ in. 15 15.0 unit load increases until 1,000 FUs are reached. At this loading Hose bibb or sill cock, ¾ in. 30 5.0 and beyond, the demand for both types of systems is the same. MARCH/APRIL 2007


CONTINUING EDUCATION: Water System Design Table 3 Demand Weight of Fixtures, in Fixture Units

Table 4 Conversion of Fixture Units to

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com Equivalent gpm

Fixture or Group Water closet Water closet Pedestal urinal Stall or wall urinal Stall or wall urinal Lavatory Bathtub Shower head Service sink Kitchen sink Water closet Water closet Lavatory Bathtub Shower head Bathroom group Bathroom group Separate shower Kitchen sink Laundry tray Combination fixture

Type of Supply Occupancy Control Public Flush valve Public Flush tank Public Flush valve Public Flush valve Public Flush tank Public Faucet Public Faucet Public Mixing valve Office, etc. Faucet Hotel or restaurant Faucet Private Flush valve Private Flush tank Private Faucet Private Faucet Private Mixing valve Private Flush valve W.C. Private Flush tank W.C. Private Mixing valve Private Faucet Private Faucet Private Faucet

Hot — — — — — 1.5 3 3 3 3 — — .75 1.5 1.5 2.25 2.25 1.5 1.5 2 2

Figure 5 Conversion of Fixture Units to gpm

Figure 6 Conversion of Fixture Units to gpm (enlarged scale)


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Fixture Units Cold Total 10 10 5 5 10 10 5 5 3 3 1.5 2 3 4 3 4 3 4 3 4 6 6 3 3 .75 1 1.5 2 1.5 2 6 8 4.5 6 1.5 2 1.5 2 2 3 2 3

Demand (Load) Fixture Units 1 2 3 4 5 6 8 10 12 14 16 18 20 25 30 35 40 45 50 60 70 80 90 100 120 140 160 180 200 225 250 275 300 400 500 750 1,000 1,250 1,500 1,750 2,000 2,250 2,500 2,750 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Demand (Load), gpm System with Flush Tanks 0 1 3 4 6 5 6.5 8 9 11 12 13 14 17 20 23 25 27 29 32 35 38 41 44 48 53 57 61 65 70 75 80 85 105 125 170 208 240 267 294 321 348 375 402 432 525 593 643 685 718 745 769

Demand (Load), gpm System with Flush Valves — — — — — — — 27 29 30 32 33 35 38 41 44 47 49 52 55 59 62 65 68 73 78 83 87 92 97 101 106 110 126 142 178 208 240 267 294 321 348 375 402 432 525 593 643 685 718 745 769

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drainage fixture unit values. The discharge rates of cer-

Figure 7 Conversion of Fixture Units to gpm (Mixed System)

Simpo PDF Merge and Split Unregistered Version - http://www.simpopdf.com tain fixtures are entirely different from the rate at which water is supplied, e.g., bathtubs. The loading effect is therefore different on the drainage system than it is on the water supply system for specific fixtures. For supply outlets that are likely to impose continuous demands, estimate the continuous demand separately from the intermittent demand and add this amount in gallons per minute to the demand of the fixtures in gallons per minute. It should be kept in mind when calculating maximum probable demands that, except for continuous demands, fixture unit values are always added, never gpm values. For example, if the maximum probable demand for two branches is required and one branch has a load of 1250 FU and the other 1750 FU, it would be wrong to add 240 gpm + 294 gpm to obtain 534 gpm for the total demand. The correct procedure is to add 1250 FU + 1750 FU to obtain a total FU value of 3000 and then from Table 4 determine the correct peak demand as 432 gpm. The 432 gpm value reflects the proper application of the theory of probability. The following example illustrates the procedure for sizing a system.

Example 1

For hot water piping and where there are no flush valves on the cold water piping, the demand corresponding to a given number of fixture units is determined from the values given for the flush tank system. The accuracy of Hunter’s curve, however, has come into serious question. Results utilizing the curve have proven to be as much as 100% inflated in some instances. The consistent overdesign, however, should in no way be interpreted as indicating that Hunter’s basic research and approach are incorrect. His method is demonstrably accurate, but it must be remembered that his basic assumptions and criteria were promulgated more than 60 years ago. Many things have changed, and changed drastically, in the interim. Improvements have been made in flush valve design as well as in faucets and fixtures. Social customs and living patterns have changed. The public emphasis on water and energy conservation has altered many basic criteria. It is now necessary to change some of Hunter’s basic assumptions (but not his concept). It has been demonstrated by thousands of projects operating satisfactorily that it is safe to reduce the values obtained by use of Hunter’s curve by 40%. It is stressed again that this reduction can be applied only for systems with a large number of fixtures. The opposite is true for water use in toilet facilities where large numbers of people gather, such as sport facilities and auditoriums. In these types of facilities, demand flow rates will exceed those determined by Hunter’s curve because many people will use the toilet rooms during breaks in the game or performance. The student is again warned to use the table of fixture unit values in the code applicable to the locality of the project. The values vary slightly from code to code. The student is also alerted to the fact that water supply fixture units are not the same as

Determine the peak demands for hot and cold and total water for an office building that has 60 flush valve water closets, 12 wall hung urinals, 40 lavatories, and 2 hose bibbs and requires 30 gpm for air-conditioning water makeup. From Table 3 determine the FU values: Hot Water Cold Water Total (Hot & Cold) 60 WC × 10 — 600 600 12 UR × 5 — 60 60 40 Lavs × 2 — — 80 40 Lavs × 1.5 60 60 — 60 FU 720 FU 740 FU From Table 4 or Figure 5: 60 FU = 32 gpm hot water demand 720 FU = 174 gpm cold water demand 740 FU = 177 gpm total water demand To the cold water and total water demand must be added the continuous demand: 2 hose bibbs × 5 (from Table 2) = 10 gpm Air-conditioning makeup = 30 gpm 40 gpm Then: Hot water demand: Cold water demand: 174 + 40 Total water demand: 177 + 40

= 32 gpm = 214 gpm = 217 gpm

The conversion of fixture unit loads to equivalent gallons per minute demand was obtained from Table 4 using straight line interpolations to obtain intermediate values. Total water demand is required for sizing the water service line for the building and also for the cold water piping inside the building up to the point where the connection is taken off to the hot water heater supply. ✺

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Now Online!



The March/April 2007 continuing education article is “Water System Design,” Chapter 13 of Engineered Plumbing Design II by A. Cal Laws, PE, CPD. The objective in designing the water supply systems for any project is to ensure an adequate water supply at adequate pressure to all fixtures and equipment at all times and to achieve the most economical sizing of the piping. There are at least six important reasons why proper design of water distribution systems is absolutely essential: health, pressure, flow, water, pipe failure, and noise. This chapter describes how to design an effective water system keeping these factors in mind, focusing on pressure, flow, and demand. You may locate this article at www.psdmagazine.org. Read the article, complete the following exam, and submit your answer sheet to the ASPE office to potentially receive 0.1 CEU.

CE Questions—“Water System Design” (PSD 138)

PSD 138


1. The flow of water through two parallel circuits of different pipe sizes results in a pressure loss _________. a. of equal proportions in each circuit b. higher in the circuit with the smaller pipe size c. lower in the circuit with the larger pipe size d. that is double compared to a single piping run

7. The empirical method is _________. a. based on arbitrary decisions b. cannot be duplicated c. allowed only by the most out-of-date codes d. used only by the most senior and the most junior of designers

2. The accuracy of Hunter’s Curve has been proven to be _________ percent inflated. a. 25 b. 50 c. 75 d. 100

8. Research is required to _________. a. determine the actual minimum flow required for each fixture type b. satisfy the psychological requirements of the users c. provide the necessary sanitary requirements d. all of the above

3. The coefficient of friction is the measurement of _______ in piping. a. pressure drop b. velocity c. roughness or smoothness d. none of the above

9. The pressure that exists in a piping network at any point when water is flowing is considered _________. a. static Pressure b. residual Pressure c. flow pressure d. none of the above

4. Flow rates shown in Figure 2 are _________. a. generally accepted by system designers b. hopelessly outdated c. unreasonable for use in designing systems d. b and c

10. The probability method _________. a. works for all plumbing systems b. unanimously accepted by plumbing engineers c. should not be used for small numbers of fixtures d. a and b

5. Pipe failure can be caused by corrosion from _________. a. contaminated water b. excessive velocities c. softened water d. hot water

11. The two methods of sizing domestic water, empirical method and method of probability, _________. a. are contradictory b. give satisfactory results c. cannot be relied upon d. have been replaced by computer-based methods

6. The actual inside diameter of 2½-inch Type K copper tube is _________. a. 2.435 inches b. 2.465 inches c. 2.469 inches d. 2.500 inches


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12. An automatic flow control orifice is designed to _______. a. regulate pressure b. deliver constant flow c. restrict pressure d. increase pressure

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Signature Expiration date: Continuing education credit will be given for this examination through March 31, 2008. Applications received after that date will not be processed.



Signature

Water System Design (PSD 138)

Questions appear on page . Circle the answer to each question. Q 1. A B C D Q 2. A B C D Q 3. A B C D Q 4. A B C D Q 5. A B C D Q 6. A B C D Q 7. A B C D Q 8. A B C D Q 9. A B C D Q 10. A B C D Q 11. A B C D Q 12. A B C D


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Water System Design (PSD 138) Was the material new information for you? ❏ Yes ❏ No Was the material presented clearly? ❏ Yes ❏ No Was the material adequately covered? ❏ Yes ❏ No Did the content help you achieve the stated objectives? ❏ Yes ❏ No Did the CE questions help you identify specific ways to use ideas presented in the article? ❏ Yes ❏ No How much time did you need to complete the CE offering (i.e., to read the article and answer the post-test questions)?___________________

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Plumbing Systems Advanced

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