Pex plumbing pdf download

Connect in three steps - Fast. Guarantee a secure, watertight joint The binding is so secure that it improves over time, as the pipe and the ring are in constant adaptation and tightening to the fitting Corrosion resistant Minimal loss of pressure Wide range of Manifolds, fittings and accessories help optimise system design. Tap water connection.

Radiator connection. Manifold installation. More details in the product catalogue. Uponor product catalogue. Aqua pipe The intelligent flushing station.

Radi pipe For heating with radiators or cooling with fan-coils. Combi pipe One pipe for drinking water and heating. Brass fittings Mettal fittings. Manifiolds Manifolds and accessories. Expansion tool Milwaukee expansion tools. Shielded couplings may be installed above ground or underground, as intended by the manufacturer.

Mechanical unshielded couplings using thermoplastic elastomer gaskets shall consist of a rigid or semi- rigid sealing sleeve and corrosion-resisting metal screw clamping bands. The pipe shall be supported on both sides of the coupling within 18 inches of the centerline of the coupling.

Mechanical unshielded couplings using thermo- plastic elastomer gaskets shall be permitted aboveground or underground. Flexible unshielded couplings shall consist of an elastomeric sealing sleeve and corrosive-resisting metal screw clamping bands. Couplings installed aboveground shall include center stops. Threaded Joints: Threaded joints for connecting plastic drainage piping to other materials shall be made with proper male or female threaded plastic adapters.

Joints shall not be over-tightened. After hand tightening, one-half to one full turn shall be made with a strap wrench. Solid Wall Plastic Pipe to Cast-iron Hub Ends: Joints shall be made by caulking the plastic pipe into the hub end with molten lead and oakum or by use of a compression gasket that is compressed when the plastic pipe is inserted into the hub end.

Joints shall be permitted to be made with or without a hub end plastic adapter. Adapters without a caulking bead shall be permitted.

Cellular Core Plastic Pipe to Cast-iron Hub Ends: Joints shall be made by caulking a solid plastic adapter into the cast-iron hub end with molten lead and oakum or by use of a compression gasket that is compressed when the plastic pipe is inserted into the hub end.

Cel- lular core plastic pipe shall not be lead caulked. Transition ce- ment shall not be permitted to be used within buildings. Transition joints shall be a minimum of 3 feet outside of buildings. Connections between drainage piping and wall hung water closets shall be made by means of an approved extension nipple or horn adapter.

Exterior wall openings shall be made watertight. Fixtures shall not be double-trapped unless a relief vent is provided between the two traps. Note: Interceptors in Chapter 6 that do not provide the required trap seal shall be provided with a separate trap. No trap shall be larger than the drainage pipe into which it discharges. Integral traps shall conform to appropriate standards. Solid connections, slip joints, or couplings may be used on the trap inlet, trap outlet, or within the trap seal.

See Section 7. Each build- ing trap when installed shall be provided with a cleanout and with a relieving vent or fresh air intake on the inlet side of the trap that shall be at least one-half the diameter of the drain to which it connects.

Such reliev- ing vent or fresh air intake shall be carried above grade and terminate in a screened outlet located outside the building. The following types of traps shall be prohibited: 1. Traps that depend upon moving parts to maintain their seal. Bell traps. Crown vented traps. Drum traps.

Hair interceptors, precious metal interceptors and similar appurtenances shall be permitted as required. Traps that could lose their seal due to evaporation because of infrequent use shall have accessible means to replenish the trap seal or be connected to a trap primer conforming to ASSE or ASSE In addition to the priming requirements of Section 5. Cleanouts in horizontal drainage lines shall be spaced at intervals not exceeding the following values: 4" pipe size or less: 75 feet 5" size and larger: feet b.

The distance referred to in Sections 5. Rain leaders and conductors connected to a building storm sewer shall have a cleanout installed at the base of the outside leader or inside conductor before it connects to the horizontal drain. There shall be a cleanout near the junction of a building drain and building sewer either inside or outside the building wall. Cleanouts shall be placed in the building sanitary sewer and the building storm sewer at the property line and brought to the surface in accordance with the requirements of the Adopting Agency.

Table 5. Manholes shall be provided as cleanouts for building sewers 12" size and larger. Manholes shall be pro- vided at every change of size, alignment, direction, grade, or elevation. The distance between manholes shall not exceed feet. Manholes may be provided in lieu of cleanouts in underground building sewers, building drains, and branches thereof, 8" size and larger. Such manholes shall comply with the requirements of Section 5.

If manholes are installed indoors, they shall have a bolted, gas-tight cover. Manhole construction shall comply with the standards of the Authority Having Jurisdiction. Cleanouts smaller than 3 inches shall be so installed that there is a 12" clearance for rod- ding.

Where it is necessary to conceal a cleanout plug, a covering plate or access door shall be provided that will permit access to the plug. Equipment shall be properly vented if loss of its trap seal is possible. Liquid waste treatment equipment shall be so installed that it is accessible for the removal of covers and the performance of necessary cleaning, servicing and maintenance.

The need to use ladders or move bulky objects in order to service interceptors and other liquid waste treatment equipment shall constitute a violation of accessibility. Grease interceptors shall comply with the requirements of the Adopting Agency. Grease interceptors include the following types: 1. Type I Hydro-mechanical interceptors 2. Grease removal or recovery devices GRD 3. Type II Gravity interceptors c. Hydro-mechanical interceptors up to gallons per minute capacity shall comply with the performance, testing, and installation requirements of ASME A These interceptors shall be sized according to Section 6.

Outdoor underground gravity grease interceptors serving commercial kitchens shall be sized and designed by a registered design professional who is licensed to practice in the particular jurisdiction.

Gravity grease interceptors shall comply with the requirements of the Adopting Agency, including materials of construction, arrangement, minimum size, and retention time.

Where food waste grinders discharge through a hydro-mechanical or GRD grease interceptor, a solids separator shall be installed either in the drain line from the food waste grinder or upstream of the grease interceptor to prevent food waste particles from entering the grease interceptor. Solids separators shall not be required where food waste grinders discharge to a gravity grease interceptor.

Commercial dishwashers shall be permitted to discharge through a grease interceptor. Sinks or sink compartments used for sanitizing pots or other ware shall not be drained through a grease interceptor. All compartments of multi-compartment sinks shall be considered to drain simultaneously, except that sanitizing compartments shall not be drained through a grease interceptor.

Table 6. Such contaminants shall be removed by an ap- propriate separator. Such locations include, but are not limited to, car or truck washing facilities, engine cleaning facilities, and similar operations.

Drains shall not be required in service or repair garages that employ dry absorbent cleaning methods; however, if any drains are located in such areas, they shall discharge to the sanitary sewer through a sand interceptor and oil interceptor.

Any storm water shall be drained separately and directly to the storm sewer. Such drainage, including melting snow, ice or rainwater runoff from vehicles, shall not be connected to the sani- tary sewer.

Where oil separators include a waste holding tank, it shall not be used to store or contain any other waste oil e. Field-fabricated oil separators shall have a depth of not less than two feet below the invert of the dis- charge outlet. The outlet opening shall have a water seal depth of not less than 18 inches.

Oil separators shall have a 3-inch minimum discharge line and a 2-inch minimum vent to atmosphere. The discharge line shall have a full-size cleanout extended to grade or otherwise be accessible. Pumps shall be adequately sized, explosion-proof, and accessible. Sand inter- ceptors shall comply with Section 6.

A sand interceptor shall be installed upstream from an oil separator if required in Section 6. A sand interceptor shall be provided downstream from any drain whose discharge may contain sand, sediment, or similar matter on a continuing basis that would tend to settle and obstruct the piping in the drainage system.

The outlet pipe of a sand interceptor shall be the same size as the drain served. The inlet to the interceptor shall be at the same elevation as, or higher than, the outlet. The bottom of the inlet section shall be at least 24 inches below the invert of the outlet pipe.

A solid removable cover shall cover the outlet section. A cleanout shall be provided for the outlet line. Solids interceptors shall be provided where necessary to prevent harmful solid materials from entering the drainage system on a continuing basis.

Solids interceptors shall separate solids by gravity, trapping them in a removable bucket or strainer. Neutralizing or dilution tanks shall be provided where necessary to prevent acidic or alkaline waste from entering the building drainage system.

Such waste shall be neutralized or diluted to levels that are safe for the piping in the drainage and sewer systems. Vents for neutralizing or dilution tanks shall be constructed of acid-resistant piping and shall be indepen- dent from sanitary system vents. No strain shall be transmitted to the connecting piping. Fastening screws or bolts shall be corrosion-resisting. In addition to the wall support brackets, pedestals or legs may provide additional support for pedestal lavatories.

Such access is not required for connections that are sol- dered, threaded, solvent cemented, or equivalently secured. Waterless non-water urinals shall have a liquid trap seal as required by Section 5. Lavatories shall comply with the following standards: 1. Except as required under Section 7. Public lavatory faucets, other than the metering type, shall be designed and manufactured according to ASME A Metering faucets shall deliver not more than 0.

A strainer, pop-up stopper, crossbar grid, or other device shall be provided to protect the waste outlet. Bathtubs shall comply with the following standards: 1. Waste outlets shall be equipped with a pop-up waste, chain and stopper, or other type of drain plug. Surrounding wall construction shall be in accordance with Section 7. Riser pipes to shower heads shall be secured in accordance with Section 7. The provisions for wet vent- ing in Section The minimum outside rough-in dimension for shower bases and prefabricated shower compartments shall be 32 inches, except where a shower receptor has a minimum overall dimension of 30 inches mm in width and 60 inches 1, mm in length.

The walls in shower compartments and above built-in bathtubs having installed shower heads shall be constructed of smooth.

Manufactured shower pans, shower bases, and shower receptors shall be installed in accordance with this Code and the manufacturer's instructions. Sinks shall comply with the following standards: 1. Each compartment in a kitchen sink or bar sink shall have an outlet suitable for either a domestic food waste grinder or a basket strainer. Service sinks and mop receptors shall have removable strainers and waste outlet connections not less than 2" nominal size. Weep hole drains that form a cross connection between ground water and the potable water supply shall not be permitted.

Such units may connect to a kitchen sink drain outlet, as permitted under Section 7. The water supply to dish- washing machines shall be protected from back-siphonage by an integral air gap or other internal means. The discharge line from the dishwasher shall be not less than the size recommended by the dishwasher manufacturer.

The discharge may also drain indirectly into a trapped standpipe, or receptor. Commercial dishwashing machines shall be indirectly connected to the drainage system through either an air gap or an air break. Commercial dishwashers shall be permitted to discharge through a grease interceptor in accordance with Section 6. Where traps are automatically primed, the priming connection shall be above the weir of the trap.

Floor drains shall be not less than 2" nominal size. Floor drains shall be installed in the following areas: 1. Toilet rooms containing either two or more water closets or wall hung urinals or a combination of one or more water closets and wall hung urinals, except in a dwelling unit.

Commercial kitchens. Common laundry rooms in commercial buildings and buildings having more than two dwelling units. The water supply connection shall be protected from back-siphonage in accordance with Chapter Examples of such special installations include decorative fountains, ornamental pools, waterfalls, swimming and wading pools, baptisteries, and similar custom-built equipment.

Ballcocks shall be the anti-siphon type and comply with ASSE Flushometer valves shall be accessible for maintenance and repair. Water closets shall be the elongated type with integral or separate seats.

Plans for plumbing systems, where required, shall indicate the maximum number of persons to be served by the facilities. In occupancies having established seating, such as auditoriums and restaurants, the number of occupants for plumbing purposes shall not be less than the number of seats. The lavatories required by Tables 7. Separate toilet facilities shall be provided for each sex. Residential installations.

In occupancies serving 15 or fewer people, one toilet facility, designed for use by no more than one person at a time, shall be permitted for use by both sexes. Drinking Water Facilities: A kitchen or bar sink shall be considered as meeting the requirements for drinking water facilities for employees. Laundry Trays: Multiple dwelling units or boarding houses without public laundry rooms shall not require laundry trays.

Service Sinks: Service sinks may be omitted when the Authority Having Jurisdiction determines that they are not necessary for proper cleaning of the facility. Types of occupancies not shown in Table 7. Where swimming pools operated by an apartment building, condominium, or similar multi-family dwelling unit are restricted to the use of residents and guests of residents of dwelling units in the immedi- ate vicinity of the pool, the minimum required toilet facilities for bathers within the pool compound shall be one 1 male toilet room and one 1 female toilet room, each consisting of a water closet and lavatory as a minimum.

Requirements for customers and employees shall be permitted to be met with a single set of restrooms accessible to both groups. Fixtures for customer use shall be permitted to be met by providing a centrally located facility accessible to several stores. The maximum distance of entry from any store to this facility shall not exceed feet.

The maxi- mum distance of entry from any store to this facility shall not exceed feet. Drinking water facilities are not required for customers where normal occupancy is short term.

Food service establishments with an occupant load of or more customers shall be provided with separate toilet facilities for employees and customers. Customer and employee toilet facilities may be combined for customer loads of or less. For employees of 15 or less, one toilet facility, designed for use by no more than one person at a time, shall be permitted for use by both sexes.

Drinking water facilities are not required in restaurants or other food service establishments if drinking water service is provided. Waste discharge from such equipment shall enter the drainage system through an air gap. Types of entrapment can include, but not be limited to, rigid, non-giving protrusions, wedge-shaped openings, and any arrangement of components that could pinch and entrap the user.

The suction inlets shall be piped so that water is drawn through the inlets simultaneously by a common suction line to the pump. Blocking one suction inlet shall not create excessive suction at other suction inlets. The equipment installer shall assemble and install the equipment in accordance with the manufacturer's instructions. See Notes: 4, 14,16 b Prisons, jails and reformatories long term. Moderated hazard. For accessible requirements, see local, state, or national codes.

Drinking fountains are not required in restaurants or other food service establishments if drinking water service is available. Drinking water is not required for customers where normal occupancy is short term. A kitchen or bar sink may be used for employee water drinking facilities. Fixtures for public use as required by this section may be met by providing a centrally located facility accessible to several stores.

The maximum distance from entry to any store to this facility shall not exceed feet. The maximum distance from entry to any store from this facility shall not exceed feet. Multiple dwellings or boarding houses without public laundry rooms shall not require laundry trays. Reserved Requirements for employees and customers may be met with a single set of restrooms. If the design number of customers in food handling establishments exceeds , separate facilities for employees and customers are required.

All showers and lavatories shall have thermostatic control and timing devices. Laboratories in higher education facilities shall have safety showers. Warehouse storage area requirements shall be permitted to be met by providing a facility centrally located within the storage area.

The maximum travel distance to the facility shall not exceed feet. Showers may be omitted in recreational facilities without locker rooms when approved by the Authority Having Jurisdiction.

Fixtures, appliances and equipment shall be connected to support the weight of the device and any ad- ditional probable loads that may impact on the device. Fixtures shall be rigidly supported so that no strain is transmitted in the piping connections. Cast-iron soil pipe—at base and at each story height. Steel threaded pipe—at every other story height.

Copper tube—at each story height but not more than foot intervals. Lead pipe—four-foot intervals. Plastic pipe—see Section 8. Flexible plastic tubing—each story height and at mid-story.

Stainless steel drainage pipe—at each story height. Cast-iron soil pipe—minimum of one hanger per pipe length located within 18 inches of each joint up to foot maximum pipe length , at changes in direction, and at branch connections.

Where pipe is sus- pended by non-rigid hangers more than 18 inches long, provide lateral support at foot maximum spacing.

Lateral support shall consist of either 1 a sway brace or 2 either a change in direction or a branch connec- tion that provides the required lateral support. One-inch size and larger—foot intervals.

Lead pipe—on continuous metal or wood strips for its entire length. Flexible plastic tubing—32 inches. Stainless steel drainage pipe—10 foot intervals, changes of direction and branch connections. Piers shall be of concrete, brick, or other masonry construction.

Provision shall be made for expansion and contraction of the piping. See Sections 4. Other piping mate- rial shall be so anchored as to support the stack at the base. Plastic drain, waste, vent, and pressure pipe shall be installed and supported as recommended by the manufacturer's instructions.

Maximum horizontal support spacing shall be based on the pipe schedule or wall thickness, the pipe size, the system operating temperature, the ambient temperature, and any concentrated loads. Vertical pipe shall be maintained in straight alignment. Intermediate supports shall be provided where required for stability. Pipe shall also be supported at changes of direction or elevation. Supports shall not compress, distort, cut, or abrade the piping and shall allow free movement.

Provisions shall be made for expansion and contraction of the piping. Fixture trap arms longer than three feet shall be supported as close as possible to the trap. The spacing for vent piping shall be permitted to be based on vapor service. Such drains shall discharge sepa- rately through an air gap or, where permitted, an air break. Fixtures and appliances used for the storage, processing, preparation, serving, dispensing, or sale of food shall be drained indirectly.

Where bar sinks, glass-washing sinks, or other counter sinks cannot be vented according to the requirements of Chapter 12, they shall be permitted to each discharge separately to a trapped and vented receptor through indirect waste pipes providing either an air break or an air gap. Traps shall be provided in the indirect waste pipe when required under Section 9.

The above requirements do not apply to refrigerated food preparation areas or work rooms. Where necessary, cleanouts shall be provided in accordance with Section 5. Air conditioning condensate. Automatic clothes washer. Water treatment unit.

Water heater relief valve discharge. In a dwelling, a laun- dry sink shall be permitted to drain into the standpipe. The minimum drain pipe size for an indirect waste receptor shall be at least one pipe size larger than the indirect waste pipe that it serves. The nature of the corrosive or harmful waste and proposed method of its treatment shall be submitted to and approved by the Authority Having Jurisdiction prior to installation.

Such wastes shall be discharged to an indirect waste receptor and a means of cooling shall be provided where necessary. Indirect waste piping from air conditioning units shall be sized according to the condensate-generating capacity of the units served.

Branches from individual units shall be no smaller than the drain opening or drain connection on the unit. Traps shall be provided at each air conditioning unit or cooling coil to main- tain atmospheric pressure in the waste piping. Unless expressly prohibited by the Authority Having Jurisdiction, the point of indirect discharge for air conditioning condensate shall be one of the following: 1.

The building sanitary drainage system. The building storm drainage system. A sump pump. A subsurface absorption pit or trench. Cross connection control shall be provided at individual outlets, and where required, by containment of the premises. Each potential cross connection within the premises shall be protected. Private potable water supplies i. Piping conveying potable water shall be constructed of non-toxic material. The interior surface of a potable water tank shall not be lined, painted, or repaired with any material that will affect either the taste, odor, color or potability of the water supply when the tank is placed in or returned to service.

Minimum Size distance : The minimum required air gap shall be twice the effective opening of a po- table water outlet unless the outlet is a distance less than 3 times the effective opening away from a wall or similar vertical surface, in which case, the minimum required air gap shall be 3 times the effective opening of the outlet. In no case shall the minimum required air gap be less than that shown in Table Table Side walls, ribs or similar obstructions do not affect air gaps when spaced from inside edge of the spout opening a distance greater than three times the diameter of the effective opening for a single wall, or a distance greater than four times the diameter of the effective opening for two intersecting walls.

The effect of three or more such vertical walls or ribs has not been determined. In such cases, the air gap shall be measured from the top of the wall. Hose connection vacuum breaker - ASSE 3. Backsiphonage, Continuous Pressure, Health Hazard 1. Back Pressure, Non-Health Hazard 1. Back Pressure, Health Hazard 1. Superior systems with exceptional support Minimize risk and improve profitability with quality products and expert support through every stage of your project.

The Exploratorium at Pier 15 A unique radiant heating and cooling application uses water from the San Francisco Bay to bring Plumbing systems Pipe, fittings, multiports, adapters, valves, manifolds, stubouts, wall boxes and other accessories for hot and cold potable water systems. Radiant heating and cooling systems Pipe, fittings, adapters, valves, manifolds, supports, controls and heat-transfer panels and plates for hydronic radiant systems.

Hydronic piping systems Pipe, fittings, adapters, valves, manifolds and supports for hydronic hot-water heating and chilled-water cooling systems. These hydrants are sometimes prohibited by local or state health authorities. Float Valves. Float valves respond to a high water level to close an inlet pipe, as in a tank-type toilet. Miscellaneous Switches. Pressure switches with a low-pressure cutoff stop the pump motor if the line pressure drops to the cutoff point.

Low-flow cutoff switches are used with submersible pumps to stop the pump if the water discharge falls below a predetermined minimum operating pressure. High-pressure cut-off switches are used to stop pumps if the system pressure rises above a predetermined maximum. Paddle-type flow switches detect flow by means of a paddle placed in the pipe that operates a mechanical switch when flow in the pipe pushes the paddle.

The inadvertent contamination of a public water supply as a result of incorrectly installing plumbing fixtures is a potential public health problem in all communities. Continuous surveillance by environmental health personnel is necessary to know whether such public health hazards have developed as a result of additions or alterations to an approved system. All environmental health specialists should learn to recognize the three general types of defects found in potable water supply systems: backflow, back siphonage, and overhead leakage into open potable water containers.

If identified, these conditions should be corrected immediately to prevent the spread of disease or poisoning from high concentrations of organic or inorganic chemicals in the water. Water Heaters Water heaters Figure 9. They consist of a space for heating the water and a storage tank for providing hot water over a limited period of time. The installation port for these valves may be found on the top or on the side of the tank near the top. This fact alone should encourage individual permitting and inspection by counties and municipalities to ensure that they are installed.

Figure 9. This vent should be directed to within 6 inches of the floor, and care must be taken to avoid reducing the diameter of the vent and creating any unnecessary bends in the discharge pipe. The point is to avoid any constrictions that could slow down the steam release from the tank to avoid explosive pressure buildup. Water heaters that are installed on wooden floors should have water collection pans with a drainage tube that drains to a proper drain.

The pan should be checked on a regular basis. Tankless Water Heaters A tankless unit has a heating device that is activated by the flow of water when a hot water valve is opened. Once activated, the heater delivers a constant supply of hot water. The output of the heater, however, limits the rate of the heated water flow.

Demand water heaters are available in propane LP , natural gas, or electric models. They come in a variety of sizes for different applications, such as a whole-house water heater, a hot water source for a remote bathroom or hot tub, or as a boiler to provide hot water for a home heating system. They can also be used as a booster for dishwashers, washing machines, and a solar or wood-fired domestic hot water system [ 7 ].

The appeal of demand water heaters is not only the elimination of the tank standby losses and the resulting lower operating costs, but also the fact that the heater delivers hot water continuously. Most tankless models have a life expectancy of more than 20 years. In contrast, storage tank water heaters last 10 to 15 years. Most tankless models have easily replaceable parts that can extend their life by many years more. Drainage System Water is brought into a house, used, and discharged through the drainage system.

This system is a sanitary drainage system carrying just interior wastewater. Sanitary Drainage System The proper sizing of the sanitary drain or house drain depends on the number of fixtures it serves.

The usual minimum size is 4 inches in diameter. The materials used are usually cast iron, vitrified clay, plastic, and, in rare cases, lead. For proper flow in the drain, the pipe should be sized and angled so that the pipe is approximately half full. This ensures proper scouring action so that the solids contained in the waste will not be deposited in the pipe. ABS uses cement only. In most cases the decision will be made on the basis of which material is sold in an area.

Few areas stock both materials because local contractors usually favor one or the other. Their durability is similar. Size of House Drain. The Uniform Plumbing Code Committee has developed a method of sizing house drains in terms of fixture units.

This is the surge flow rate of water discharged from a wash basin in one minute. All other fixtures have been related to this unit. Fixture unit values are shown in Table 9. Grade of House Drain. A house drain should be sloped toward the sewer to ensure scouring of the drain.

The size of the drain is based on the fixture units flowing into the pipe and the slope of the drain. Table 9. House Drain Installation. Typical branch connections to the main are shown in Figure 9. Fixture and Branch Drains. A branch drain is a waste pipe that collects the waste from two or more fixtures and conveys it to the sewer. It is sized in the same way as the sewer, taking into account that all toilets must have a minimum 3-inch diameter drain, and only two toilets may connect into one 3-inch drain.

All branch drains must join the house drain with a Y-fitting as shown in Figure 9. The same is true for fixture drains joining branch drains. The Y-fitting is used to eliminate, as much as possible, the deposit of solids in or near the connection. A buildup of these solids will block the drain.

Recommended minimum sizes of fixture drains are shown in Table 9. All fixtures connected to a household plumbing system should have a trap installed in the line. The effects of sewer gases on the human body are well known; many of the gases are extremely harmful. In addition, certain sewer gases are explosive. The most commonly used trap is the P-trap Figure 9. The depth of the seal in a trap is usually 2 inches. A deep seal trap has a 4-inch seal. As mentioned earlier, the purpose of a trap is to seal out sewer gases from the structure.

Because a plumbing system is subject to wide variations in flow, and this flow originates in many different sections of the system, pressures vary widely in the waste lines. These pressure differences tend to remove the water seal in the trap. The waste system must be properly vented to prevent the traps from siphoning dry, thus losing their water seal and allowing gas from the sewer into the building. Objectionable Traps. Mechanical traps were introduced to counteract this problem.

It has been found, however, that the corrosive liquids flowing in the system corrode or jam these mechanical traps. For this reason, most plumbing codes prohibit mechanical traps. The bag trap, an extreme form of S-trap, is seldom found.

Traps are used only to prevent the escape of sewer gas into the structure. They do not compensate for pressure variations. Only proper venting will eliminate pressure problems. Ventilation A plumbing system is ventilated to prevent trap seal loss, material deterioration, and flow retardation. Trap Seal Loss. The seal in a plumbing trap may be lost due to siphonage direct and indirect or momentum , back pressure, evapo ration, capillary attraction, or wind effect.

The first two are probably the most common causes of loss. If a waste pipe is placed vertically after the fixture trap, as in an S-trap, the wastewater continues to flow after the fixture is emptied and clears the trap. This is caused by the pressure of air on the water of the fixture being greater than the pressure of air in the waste pipe. The action of the water discharging into the waste pipe removes the air from that pipe and thereby causes a negative pressure in the waste line.

In the case of indirect or momentum siphonage, the flow of water past the entrance to a fixture drain in the waste pipe removes air from the fixture drain.