Electric Water Heater Installation

   has its own inline trap.

A drain-waste-vent system (or DWV) is the combination of pipes and plumbing fittings that captures sewage and greywater within a structure and routes it toward a water treatment system. It includes venting to the exterior environment to prevent a vacuum from forming and impeding fixtures such as sinks, showers, and toilets from draining freely, and employs water-filled traps to block dangerous sewer gasses from entering a plumbed structure.

DWV systems capture both sewage and greywater within a structure and safely route it out via the low point of its "soil stack" to a waste treatment system, either via a municipal sanitary sewer system, or to a septic tank and leach field. (Cesspits are generally prohibited in developed areas.) For such drainage systems to work properly it is crucial that neutral air pressure be maintained within all pipes, allowing free gravity flow of water and sewage through drains. It is critical that a sufficient fall gradient (downward slope) be maintained throughout the drain pipes to keep liquids and entrained solids flowing freely from a building towards the main drain. In situations where a downward slope out of a building en route to a treatment system cannot be created, a special collection sump pit and grinding lift "sewage ejector" pump are needed. By contrast, potable water supply systems are pressurized up to 50 pounds per square inch (340 kPa) or more and so do not require a continuous downward slope in their piping to distribute water through buildings.

Every fixture is required to have an internal or external trap to prevent sewer gases from entering a structure. Double trapping is prohibited by plumbing codes due to its susceptibility to clogging. In the U.S., every plumbing fixture must also be coupled to the system's vent piping.^[1] Without a vent, negative pressure can slow the flow of water leaving the system, resulting in clogs, or cause siphonage to empty a trap. The high point of the vent system (the top of its "soil stack") must be open to the exterior at atmospheric pressure. On large systems, separate parallel vent stacks may also be run to ensure sufficient airflow, because the number of devices linked to an atmospheric vent, and their distances from it, are regulated by plumbing code.

A sewer pipe is normally at neutral air pressure compared to the surrounding atmosphere. When a column of waste water flows through a pipe, it compresses air ahead of it in the system, creating a positive pressure that must be released so it does not push back on the waste stream and downstream traps, slow drainage, and induce potential clogs. As the column of water passes, air must also freely flow in behind the waste stream, or negative pressure results, which can siphon water out of a trap after it is passed and allow noxious sewer gases to enter a building. The extent of these pressure fluctuations is determined by the fluid volume of the waste discharge.

Generally, a toilet outlet has the shortest trap seal, making it most vulnerable to being emptied by induced siphonage.

An additional risk of pressurizing a system ahead of a waste stream is the potential for it to overwhelm a downstream trap and force tainted water into its fixture. Serious hygiene and health consequences can result. Tall buildings of three or more stories are particularly susceptible to this problem. Adequate supplementary vent stacks are installed in parallel to waste stacks to allow proper venting in large and tall buildings and eliminate these pressure-related venting problems.

DWV systems are vented directly through the building roof. Increasingly DWV pipe is ABS or PVC DWV-rated plastic pipe equipped with a flashing at the roof penetration to prevent rainwater from entering the buildings. Older structures may use asbestos, copper, iron, lead or clay pipes, in rough order of era of use.

Under many older building codes, a vent stack (a pipe leading to the main roof vent) is required to be within approx. a 5-foot (1.5 m) radius of the draining fixture it serves (sink, toilet, shower stall, etc.).^[2] To allow a single roof penetration as permitted by local building code, sub-vents may be tied together inside the building and exit via a common vent stack, frequently the "main" vent. Adding a vent connection within a long horizontal run with little slope will aid flow, and when used with a cleanout allows for better serviceability.

Unlike traps for other fixtures, toilet traps are usually designed to self-siphon to ensure complete evacuation of their contents;^{[citation needed]} toilet bowls are then automatically refilled by a special valve mechanism.

In exceptional cases it is either not possible or inconvenient to vent a fixture or fixtures externally. In such cases a resort to "internal venting" may be viable, where compliant with local plumbing codes. Such alternatives include mechanical vents (also called cheater vents^[3]) such as air admittance valves and check vents, and "plumb-arounds" such as an inline vent employed in kitchen islands and similar applications:

• Air admittance valves (AAVs, or commonly referred to in the UK as Durgo valves and in the US as Studor vents and Sure-Vent®) are negative-pressure-activated, one-way mechanical valves, used in a plumbing or drainage venting system to eliminate the need for conventional pipe venting and roof penetrations. A discharge of wastewater causes the AAV to open, releasing the vacuum and allowing air to enter the plumbing vent pipe for proper pressure equalization.
   

Since AAVs will only operate under negative pressure situations, they are not suitable for all venting applications, such as venting a sump, where positive pressures are created when the sump fills. Also, where positive drainage pressures are found in larger buildings or multi-story buildings, an air admittance valve could be used in conjunction with a positive pressure reduction device such as the PAPA positive air pressure attenuator to provide a complete venting solution for more complicated drainage venting systems.
 

Using AAVs can significantly reduce the amount of venting materials needed in a plumbing system, increase plumbing labor efficiency, allow greater flexibility in the layout of plumbing fixtures, and reduce long-term roof maintenance problems associated with conventional vent stack roofing penetrations.
 

While some state and local building departments prohibit AAVs, the International Residential and International Plumbing Codes allow it to be used in place of a vent through the roof. AAVs are certified to reliably open and close a minimum of 500,000 times, (approximately 30 years of use) with no release of sewer gas; some manufacturers claim their units are tested for up to 1.5 million cycles, or at least 80 years of use. AAVs have been effectively used in Europe for more than two decades.^{[when?][where?]}
 

• Check vents employ a check valve.^{[clarification needed]}

• In-line vent (also known as an island fixture vent, and, colloquially, a "Chicago Loop", "Boston loop" or "Bow Vent") is an alternate method permissible in some jurisdictions of venting the trap installed on an under counter island sink or other similar applications where a conventional vertical vent stack or air admittance valve is not feasible or allowed.
   

As with all drains, ventilation must be provided to allow the flowing waste water to displace the sewer gas in the drain, and then to allow air (or some other fluid) to fill the vacuum which would otherwise form as the water flows down the pipe.
 

An island fixture vent allows water displaces the sewer gas up to the sanitary tee, the water flows downward while sewer gas is displaced upward and toward the vent. The vent can also provide air to fill any vacuum created.
 

The key to a functional island fixture vent is that the top elbow must be at least as high as the "flood level" (the peak possible drain water level in the sink), allowing it to serve as a de facto vacuum breaker preventing the loop from becoming a siphon for an overfilled sink, as from a clogged drain (rather than vent) line.

All DWV systems require various sized fittings and pipes which are measured by their internal diameter of both the pipes and the fittings which, and in most cases are Schedule 40 PVC wye's, tee's, elbows ranging from 90 degrees to 22.5 degrees for both inside diameter fitment (street) as well as outer diameter fitment (hub), repair and slip couplings, reducer couplings, and pipe which is typically ten feet in length. Sizes for hub fittings such as wye's and tee's are based on the inside diameter of the pipe that goes into their hubs. Items such as washer boxes and Studor vents are also measured by the internal diameter of the fittings.

Cost of materials, ease of installation, and resistance to corrosion all have come to favor Schedule 40 PVC DWV systems, which are replacing cast iron "hub" and "no-hub" DWV systems in many municipalities, while parts and skills associated with installing and maintaining cast iron systems are becoming increasingly scarce and costly.

The advent of PVC and solvent welding adhesives, which secure fittings against leakage and separation by melting the material into itself, has profoundly simplified and made installing a DWV system less expensive. As with pressurized water "supply" plumbing, all lines must be bored for where they will not compromise structural framing and properly supported inline, and all external penetrations properly sealed and flashed.

• Fink, Justin (16 September 2015). "Drain-Waste-Vent Systems". Fine Homebuilding. 154. Taunton Press: 18–19. Retrieved 25 September 2015.

 

This article may not provide balanced coverage on the world. Please improve this article or discuss the issue on the talk page. (January 2017)

Standard codes are followed when designing (or manufacturing) a piping system. Organizations which promulgate piping standards include:

• ASME: American Society of Mechanical Engineers
  • A112.19.1 Enameled cast-iron and steel plumbing fixtures standards
  • A112.19.2 Ceramic plumbing fixtures standard
• ASTM International: American Society for Testing and Materials
• API: American Petroleum Institute
• AWS: American Welding Society
• AWWA: American Water Works Association
• MSS: Manufacturers Standardization Society
• ANSI: American National Standards Institute
• NFPA: National Fire Protection Association
• EJMA: Expansion Joint Manufacturers Association
• CGA: Compressed Gas Association
• PCA: Plumbing Code of Australia

Pipes must conform to the dimensional requirements of:

• ASME B36.10M: Welded and seamless wrought-steel pipe
• ASME B36.19M: Stainless-steel pipe
• ASME B31.3 2008: Process piping
• ASME B31.4 XXXX: Power piping

The material with which a pipe is manufactured is often the basis for choosing a pipe. Materials used for manufacturing pipes include:

• Carbon (CS) and galvanized steel
• Impact-tested carbon steel (ITCS)
• Low-temperature carbon steel (LTCS)
• Stainless steel (SS)
• Malleable iron
• Chrome-molybdenum (alloy) steel (generally used for high-temperature service)
• Non-ferrous metals (includes copper, inconel, incoloy, and cupronickel)
• Non-metallic (includes acrylonitrile butadiene styrene (ABS), fibre-reinforced plastic (FRP), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), high-density polyethylene (HDPE), Cross-linked polyethylene (PEX), and toughened glass; polybutylene has also been used, but is now banned in North America because of poor reliability)

The bodies of fittings for pipe and tubing are often the same base material as the pipe or tubing connected: copper, steel, PVC, CPVC, or ABS. Any material permitted by the plumbing, health, or building code (as applicable) may be used, but it must be compatible with the other materials in the system, the fluids being transported, and the temperature and pressure inside (and outside) the system. Brass or bronze fittings are common in copper piping and plumbing systems. Fire resistance, earthquake resistance, mechanical ruggedness, theft resistance, and other factors also influence the choice of pipe and fitting materials.

Gaskets are mechanical seals, usually ring-shaped, which seal flange joints.^[3] Gaskets vary by construction, materials and features. Commonly used gaskets are non-metallic (ASME B 16.21), spiral-wound (ASME B 16.20) and ring-joint (ASME B 16.20). Non-metallic gaskets are used with flat- or raised-face flanges. Spiral-wound gaskets are used with raised-face flanges, and ring-joint gaskets are used with ring-type joint (RTJ) flanges. Stress develops between an RTJ gasket and the flange groove when the gasket is bolted to a flange, leading to plastic deformation of the gasket.^[4]

Piping or tubing is usually inserted into fittings to make connections. Connectors are assigned a gender, abbreviated M or F. An example of this is a " 3⁄4-inch female adapter NPT", which would have a corresponding male connection of the same size and thread standard (in this case also NPT).

This section discusses fittings primarily used in pressurized piping systems, though there is some overlap with fittings for low-pressure or non-pressurized systems. Specialized fittings for the latter setups are discussed in the next major subsection.

In plumbing, an adapter is generally a fitting that interfaces two different parts. The term commonly refers to:

• any fitting that connects pipes of different materials, including:^[5][6][7]
  • expansion adapters which have a flexible section to absorb expansion or contraction from two dissimilar pipe materials^[8]
  • mechanical joint (MJ) adapters for joining polyethylene pipe to another material^{[9]: 349â€Å} 
  • bell adapters which are like mechanical joint adapters but contain a stainless steel backup ring to maintain a positive seal against the mating flange^{[9]: 347â€Å} 
  • flange adapters which attach to a polyethylene pipe with butt fusion to stiffen a junction and allow another flanged pipe or fitting to be bolted on^{[9]: 341â€Å} 
• a fitting that connects pipes of different diameters, genders, or threads ( see § Coupling below)^[10]
  • adapter spools (also called crossover spools), used on oilfields and pressure control, have different diameters, pressure ratings or designs at each end^[11]
  • adapters to convert NPT to BSP pipe threads are available^[12]
• a fitting that connects threaded and non-threaded pipe^[13][14]

An elbow is installed between two lengths of pipe (or tubing) to allow a change of direction, usually a 90° or 45° angle; 22.5° elbows are also available. The ends may be machined for butt welding, threaded (usually female), or socketed. When the ends differ in size, it is known as a reducing (or reducer) elbow.

Clarity on the difference between plumbing terminologies and geometric angles:

In plumbing, the term "45-degree elbow" for example, refers to the angle of bend from the original straight pipe position (0 degrees) to the new position (45 degrees), not the actual angle formed by the joint.

On a protractor, the actual angle of the above joint is 135 degrees, an obtuse angle.

This naming convention applies to other plumbing elbows, such as:

- "88 degree elbow" = 92 degrees on a protractor. Visualise bending the left end of the pipe up 88 degrees. Now turn the piece of pipe around so the horizontal piece of pipe is in line with the zero degrees line on the protractor. The protractor will read 92 degrees.

The key point is that the plumbing term focuses on the degree of bend from the original straight pipe, not the resulting angle.

Elbows are also categorized by length. The radius of curvature of a long-radius (LR) elbow is 1.5 times the pipe diameter, but a short-radius (SR) elbow has a radius equal to the pipe diameter. Wide available short elbows are typically used in pressurized systems and physically tight locations.

Long elbows are used in low-pressure gravity-fed systems and other applications where low turbulence and minimum deposition of entrained solids are of concern. They are available in acrylonitrile butadiene styrene (ABS plastic), polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and copper, and are used in DWV systems, sewage, and central vacuum systems.

A coupling connects two pipes. The fitting is known as a reducing coupling, reducer, or adapter if their sizes differ. There are two types of collars: "regular" and "slip". A regular coupling has a small ridge or stops internally to prevent the over-insertion of a pipe and, thus, under-insertion of the other pipe segment (which would result in an unreliable connection).

A slip coupling (sometimes also called a repair coupling) is deliberately made without this internal stop to allow it to be slipped into place in tight locations, such as the repair of a pipe that has a small leak due to corrosion or freeze bursting, or which had to be cut temporarily for some reason. Since the alignment stop is missing, it is up to the installer to carefully measure the final location of the slip coupling to ensure that it is located correctly.

A union also connects two pipes but is quite different from a coupling, as it allows future disconnection of the pipes for maintenance. In contrast to a coupling requiring solvent welding, soldering, or rotation (for threaded couplings), a union allows easy connection and disconnection multiple times if needed. It consists of three parts: a nut, a female, and a male end. When the female and male ends are joined, the nut seals the joint by pressing the two ends tightly together. Unions are a type of very compact flange connector.

Dielectric unions, with dielectric insulation, separate dissimilar metals (such as copper and galvanized steel) to prevent galvanic corrosion. When two dissimilar metals are in contact with an electrically conductive solution (ordinary tap water is conductive), they form an electrochemical couple which generates a voltage by electrolysis. When the metals are in direct contact with each other, the electric current from one to the other also moves metallic ions from one to the other; this dissolves one metal, depositing it on the other. A dielectric union breaks the electrical path with a plastic liner between its halves, limiting galvanic corrosion.

Rotary unions allow mechanical rotation of one of the joined parts while resisting leakage.

A nipple is a short stub of pipe, usually male-threaded steel, brass, chlorinated polyvinyl chloride (CPVC), or copper (occasionally unthreaded copper), which connects two other fittings. A nipple with continuous uninterrupted threading is known as a close nipple. Nipples are commonly used with plumbing and hoses.

A reducer reduces the pipe size from a larger to a smaller bore (inner diameter). Alternatively, reducer may refer to any fitting which causes a change in pipe diameter.^[15] This change may be intended to meet hydraulic flow requirements of the system or adapt to existing piping of a different size. The reduction length is usually equal to the average of the larger and smaller pipe diameters. Although reducers are usually concentric, eccentric reducers are used as needed to maintain the top- or bottom-of-pipe level.

A reducer can also be used either as a nozzle or diffuser, depending on the mach number of the flow.^{[citation needed]}

A double-tapped bushing, commonly shortened to bushing, is a fitting which serves as a reducer. It is a sleeve similar to a close nipple, but is threaded on both its inner and outer circumferences. Like a reducer, a double-tapped bushing has two threads of different sizes. A common type of this style fitting is a "hex bushing" with a hex head for installation with a pipe wrench.

A double-tapped bushing is more compact than a reducer but not as flexible. While a double-tapped bushing has a more minor female thread concentric to a larger male thread (and thus couples a smaller male end to a larger female), a reducer may have large and small ends of either gender. If both ends are the same gender, it is a gender-changing reducer.

There are similar fittings for both sweat and solvent joinery. Since they are not "tapped" (threaded), they are simply called 'reducing bushings.

 

A tee combines or divides fluid flow. Tees can connect pipes of different diameters, change the direction of a pipe run, or both. Available in various materials, sizes and finishes, they may also be used to transport two-fluid mixtures.^{[further explanation needed]} Tees may be equal or unequal in size of their three connections, with equal tees the most common.

This specialized type of tee fitting is used primarily in pressurized hydronic heating systems to divert a portion of the flow from the main line into a side branch connected to a radiator or heat exchanger. The diverter tee allows the flow in the main line, even when the side branch is shut down and not calling for heat. Diverter tees must be heeded with directional markings; a tee installed backwards will function very poorly.

Crosses, also known as four-way fittings or cross branch lines, have one inlet and three outlets (or vice versa), and often have a solvent-welded sockets or female-threaded ends. Cross fittings may stress pipes as temperatures change because they are at the center of four connection points. A tee is steadier than a cross; it behaves like a three-legged stool, and a cross behaves like a four-legged stool. Geometrically, any three non-collinear points can self-consistently define a plane; three legs are inherently stable, whereas four points overdetermine a plane and can be inconsistent, resulting in physical stress on a fitting.

Crosses are common in fire sprinkler systems (where stress caused by thermal expansion is not generally an issue),^[why?] but are not common in plumbing.

 

Caps, usually liquid- or gas-tight, cover the otherwise open end of a pipe. The exterior of an industrial cap may be round, square, rectangular, U- or I-shaped, or may have a handgrip.

A plug is a short barbed fitting with a blank end that can only be used with PEX piping to end the continuation of a water line that is no longer in use due to tying in elsewhere within the system or to seal the end of a water line which may be used for future use in the case of additional facilities. All plugs are sealed watertight with a PEX crimp.

A barb (or hose barb), which connects flexible hose or tubing to pipes, typically has a male-threaded end which mates with female threads. The other end of the fitting has a single- or multi-barbed tube—a long tapered cone with ridges, which is inserted into a flexible hose.

 

Valves stop (or regulate) the flow of liquids or gases. They are categorized by application, such as isolation, throttling, and non-return.

Isolation valves temporarily disconnect part of a piping system to allow maintenance or repair, for example. Isolation valves are typically left in either a fully open or closed position. A given isolation valve may be in place for many years without being operated but must be designed to be readily operable whenever needed, including for emergency use.

Throttling valves control the amount or pressure of a fluid allowed to pass through and are designed to withstand the stress and wear caused by this operation. Because they may wear out in this usage, they are often installed alongside isolation valves which can temporarily disconnect a failing throttling valve from the rest of the system, so it can be refurbished or replaced.

Non-return or check valves allow the free flow of a fluid in one direction but prevent its flow in a reverse direction. They are often seen in drainage or sewage systems but may also be used in pressurized systems.

Valves are available in several types, based on design and purpose:

• Gate, plug, or ball valves – Isolation
• Globe valve – Throttling
• Needle valve – Throttling, usually with high precision but low flow
• Butterfly or diaphragm valves – Isolation and throttling
• Check valve – Preventing reverse flow (non-return)

Because they operate at low pressure and rely on gravity to move fluids (and entrained solids), drain-waste-vent systems use fittings whose interior surfaces are as smooth as possible. The fittings may be "belled" (expanded slightly in diameter) or otherwise shaped to accommodate the insertion of pipe or tubing without forming a sharp interior ridge that might catch debris or accumulate material, and cause a clog or blockage.^[16] Freshly cut ends of pipe segments are carefully deburred to remove projecting slivers of material which may snag debris (such as hair or fibers) which can build up to cause blockages. This internal smoothness also makes it easier to "snake out" or "rod out" a clogged pipe with a plumber's snake.

Underground piping systems for landscaping drainage or the disposal of stormwater or groundwater also use low-pressure gravity flow, so fittings for these systems resemble larger-scale DWV fittings. With high peak-flow volumes, the design and construction of these systems may resemble those of storm sewers.

Fittings for central vacuum systems are similar to DWV fittings but usually have thinner and lighter construction because the weight of the materials conveyed is less. Vacuum-system designs share with DWV designs the need to eliminate internal ridges, burrs, sharp turns, or other obstructions which might create clogs.

Slip-joint fittings are frequently used in kitchen, bathroom and tub drainage systems. They include a detached (movable) slip nut and slip-joint washer; the washer is made of rubber or nylon.^[17] An advantage of this type of fitting is that the pipe it is connecting to does not need to be cut to a precise length; the slip joint can attach within a range of the end of the inserting pipe. Many slip fittings may be tightened or loosened by hand for easier access to residential drainpipe systems (for example, to clean out a trap or access a drain line past a trap).

DWV elbows are usually long-radius ("sweep") types.^{[18]: 61â€Å}  To reduce flow resistance and solid deposits when the direction of flow is changed, they use a shallow curve with a large radius of curvature.^{[18]: 61 [19]} In addition, a well-designed system will often use two 45° elbows instead of one 90° elbow (even a sweep 90° elbow) to reduce flow disruption as much as possible.^{[18]: 61â€Å} 

Central vacuum system inlet fittings are intentionally designed with a tighter curvature radius than other bends in the system. If vacuumed debris becomes stuck, it will jam at the inlet, where it is easy to find and remove.

A closet flange (the drainpipe flange to which a flush toilet is attached) is a specialized flange designed to be flush with the floor, allowing a toilet to be installed above it. The flange must be mechanically strong to accommodate slight misalignments or movements and resist corrosion.

Clean-outs are fittings with removable elements, allowing access to drains without removing plumbing fixtures. They are used to allow an auger (or plumber's snake) to clean out a plugged drain. Since clean-out augers are limited in length, clean-outs should be placed in accessible locations at regular intervals throughout a drainage system (including outside the building). Minimum requirements are typically at the end of each branch in piping, just ahead of each water closet, at the base of each vertical stack and inside and outside the building in the main drain or sewer. Clean-outs usually have screw-on caps or screw-in plugs. They are also known as "rodding eyes", because of the eye-shaped cover plates often used on external versions.

A trap primer automatically injects water into a trap, maintaining a water seal to keep sewer gas out of buildings. It must be installed in an easily accessible place for adjustment, replacement, and repair. A trap primer, a specialized valve, is usually connected to a clean-water supply in addition to a DWV system.^[20] Because of the dual connection, it must be designed to resist the accidental backflow of contaminated water.

A combination tee (combo tee, combo wye, tee-wye, long-sweep wye, or combi) is a tee with a gradually curving central connecting joint: a wye plus an additional 1/8 bend (45°), combined in one 90° unit. It is used in drains for a smooth, gradually curving path to reduce the likelihood of clogs, to ease the pushing of a plumber's snake through a drain system and to encourage water flow in the direction of the drain.^{[21]: 165â€Å} 

A sanitary tee has a curved center section. In drainage systems, it is primarily used to connect horizontal drains (including fixture trap arms) to vertical drains. The center connection is generally to the pipe leading to a trap (the trap arm). It must not connect a vertical drain to a horizontal drain because of the likelihood that solids will accumulate at the bottom of the junction and cause a blockage.

Also called a tee with a diverter baffle, a waste tee or an end-outlet tee, it typically connects waste lines before they enter the trap and has a baffle to keep water from one waste pipe from entering the other at the connection.^[22]

This fitting differs from a standard cross in that two ports have curved inlets. Although it has been used in the past for connecting the drains of back-to-back fixtures (such as back-to-back sinks), some current codes—including the 2006 Uniform Plumbing Code in the United States—prohibit the use of this fitting for that purpose and require a double-fixture fitting (double combination wye) to minimize wastewater from one side flowing into the other.

 

Tee-wyes are similar to tees, except for angling the branch line to reduce friction and turbulence. They are commonly used to attach a vertical drainpipe to a horizontal one, reducing the deposition of entrained solids at the junction.^{[21]: 159, 165 [21]: 165 [23]} Wyes and combo wyes follow a long-sweep pattern relative to sanitary tees and other short-sweep bends, which have a smaller radius and require less space.^{[21]: 165â€Å} 

Wyes also have industrial applications. Although low-priced wyes are often spot-welded, industrial-strength wyes are flash-welded at each seam. In long-distance pipeline applications, a specialized wye is used to allow insertion of pigging to keep pipes clear and flowing.

This fitting (also known as a "bungalow fitting" or a "cottage fitting") is a sanitary tee that allows two trap arms to be connected at the same level. A toilet is the main connection, with the option of a right or left-hand outlet to the 3" inlet with a choice of 1-1/2" or 2" in size. It is used to keep stack-vented fixtures high to the joist space and thus conserves the headroom in a basement. As the water closet must be the lowest fixture, the smaller side outlet (usually used to connect the bathtub trap arm) enters slightly above the larger connection.^{[citation needed]}

Hydraulic systems use high fluid pressure, such as the hydraulic actuators for bulldozers and backhoes. Their hydraulic fittings are designed and rated for much greater pressure than that experienced in general piping systems, and they are generally not compatible with those used in plumbing. Hydraulic fittings are designed and constructed to resist high-pressure leakage and sudden failure.

Much of the work of installing a piping or plumbing system involves making leakproof, reliable connections, and most piping requires mechanical support against gravity and other forces (such as wind loads and earthquakes) which might disrupt an installation.^[24] Depending on the connection technology and application, basic skills may be sufficient, or specialized skills and professional licensure may be legally required.

Fasteners join, or affix, two or more objects. Although they are usually used to attach pipe and fittings to mechanical supports in buildings, they do not connect the pipes. Fasteners commonly used with piping are a stud bolt ^[25] with nuts (usually fully threaded, with two heavy, hexagonal nuts); a machine bolt and nut; or a powder-actuated tool (PAT) fastener (usually a nail or threaded stud, driven into concrete or masonry).

A threaded pipe has a screw thread at one or both ends for assembly. Steel pipe is often joined with threaded connections; tapered threads are cut into the end of the pipe, and sealant is applied in the form of thread-sealing compound or thread seal tape (also known as PTFE or Teflon tape) and the pipe is screwed into a threaded fitting with a pipe wrench.

Threaded steel pipe is widely used in buildings to convey natural gas or propane fuel and is also a popular choice in fire sprinkler systems due to its resistance to mechanical damage and high heat (including the threaded joints). Threaded steel pipe may still be used in high-security or exposed locations because it is more resistant to vandalism, more difficult to remove, and its scrap value is much lower than copper or brass.

A galvanized coating of metallic zinc was often used to protect steel water pipes from corrosion, but this protective coating eventually would dissolve away, exposing the iron to deterioration. Pipes used to convey fuel gas are often made of "black iron", which has been chemically treated to reduce corrosion, but this treatment does not resist erosion from flowing water. Despite its ruggedness, steel pipe is no longer preferred for conveying drinking water because corrosion can eventually cause leakage (especially at threaded joints), deposits on internal surfaces will eventually restrict flow, and corrosion will shed black or rusty residues into the flowing water.

These disadvantages are less problematic for fire sprinkler installations because standing water in the steel pipes does not flow, except during occasional tests or activation by a fire. Introducing oxygen dissolved in freshwater supplies will cause some corrosion, but this soon stops without any source of additional water-borne oxygen.

In older installations, the threaded brass pipe was similarly used and was considered superior to steel for drinking water because it was more resistant to corrosion and shed much fewer residues into the flowing water.

Assembling threaded pipe is labor-intensive, and requires skill and planning to allow lengths of pipe to be screwed together in sequence. Most threaded-pipe systems require strategically located pipe-union fittings in final assembly. The threaded pipe is heavy and requires adequate attachment to support its weight.

To ensure a comprehensive pressure test, it is crucial to explicitly request a 3.1 certificate in accordance with EN HFF 10204:2004. This certificate attests that the 'metallic products' meet the stipulated order requirements and provides detailed test results. Typically, each fitting is associated with a unique heat number, which corresponds to the information documented in the 3.1 certificate datasheet.^[26][27]

A solvent is applied to PVC, CPVC, ABS or other plastic piping to partially dissolve and fuse the adjacent surfaces of piping and fitting. Solvent welding is usually used with a sleeve-type joint to connect pipe and fittings made of the same (or compatible) material.

Unlike metal welding, solvent welding is relatively easy to perform (although care is needed to make reliable joints). Solvents typically used for plastics are usually toxic^{[citation needed]} and may be carcinogenic^{[citation needed]} and flammable, requiring adequate ventilation.

To make a solder connection, a chemical flux is applied to the inner sleeve of a joint and the pipe is inserted. The joint is then heated, typically by using a propane or MAPP gas torch, although electrically heated soldering tools are sometimes used. Once the fitting and pipe have reached sufficient temperature, solder is applied to the heated joint, and the molten solder is drawn into the joint by capillary action as the flux vaporizes. "Sweating" is a term sometimes used to describe the soldering of pipe joints.^{[citation needed][28]}

Where many connections must be made in a short period (such as plumbing of a new building), soldering is quicker and less expensive joinery than compression or flare fittings. A degree of skill is needed to make several reliable soldered joints quickly. If flux residue is thoroughly cleaned, soldering can produce a long-lasting connection at a low cost. However, using an open flame for heating joints can present fire and health hazards to building occupants and requires adequate ventilation.

 

The welding of metals differs from soldering and brazing in that the joint is made without adding a lower-melting-point material (e.g. solder); instead, the pipe or tubing material is partially melted, and the fitting and piping are directly fused. This generally requires piping and fitting to be the same (or compatible) material. Skill is required to melt the joint sufficiently to ensure good fusion while not deforming or damaging the joined pieces.

Properly welded joints are considered reliable and durable. Pipe welding is often performed by specially licensed workers whose skills are retested periodically. For critical applications, every joint is tested with nondestructive methods. Because of the skills required, welded pipe joints are usually restricted to high-performance applications such as shipbuilding, and in chemical and nuclear reactors.

Adequate ventilation is essential to remove metal fumes from welding operations, and personal protective equipment must be worn. Because the high temperatures during welding can often generate intense ultraviolet light, dark goggles or full face shields must be used to protect the eyes. Precautions must also be taken to avoid fires caused by stray sparks and hot welding debris.

Compression fittings (sometimes called "lock-bush fittings") consist of a tapered, concave conical seat; a hollow, barrel-shaped compression ring (sometimes called a ferrule); and a compression nut which is threaded onto the body of the fitting and tightened to make a leakproof connection. They are typically brass or plastic, but stainless steel or other materials may be used.

Although compression connections are less durable than soldered (aka sweated) connections, they are easy to install with simple tools. However, they take longer to install than soldered joints and sometimes require re-tightening to stop slow leaks which may develop over time. Because of this possible leakage, they are generally restricted to accessible locations (such as under a kitchen or bathroom sink) and are prohibited in concealed locations such as the interiors of walls.

Push-to-pull fittings are easily removed compression fitting that allows pipes to be connected with minimal tools. These fittings are similar to regular compression fittings but use an O-ring for sealing and a grip ring to hold the pipe. The main advantage is that it can easily be removed and re-used, it is easy to assemble, and the joints are still rotatable even after assembly. The pipe end should be square, so it sits against the stop in the fittings and does not create turbulence, and needs to be a clean cut to avoid damaging the O-ring during insertion.^[29]

Flared connectors should not be confused with compression connectors, which are generally not interchangeable. Lacking a compression ring, they use a tapered conical shaped connection instead. A specialized flaring tool is used to enlarge tubing into a 45º tapered bell shape matching the projecting shape of the flare fitting.^{[21]: 82â€Å}  The flare nut, which had previously been installed over the tubing, is then tightened over the fitting to force the tapered surfaces tightly together. Flare connectors are typically brass or plastic, but stainless steel or other materials may be used.

Although flare connections are labor-intensive, they are durable and reliable. Considered more secure against leaks and sudden failure, they are used in hydraulic brake systems and in other high-pressure, high-reliability applications.

Flange fittings are generally used to connect valves, inline instruments or equipment nozzles. Two surfaces are joined tightly together with threaded bolts, wedges, clamps, or other means of applying high compressive force.^[30] Although a gasket, packing, or O-ring may be installed between the flanges to prevent leakage, it is sometimes possible to use only a special grease or nothing at all (if the mating surfaces are sufficiently precisely formed). Although flange fittings are bulky, they perform well in demanding applications such as large water supply networks and hydroelectric systems.

Flanges are rated at 150, 300, 400, 600, 900, 1500, and 2500 psi; or 10, 15, 25, 40, 64, 100, and 150 bars of pressure. Various types of flanges are available, depending on construction. Flanges used in piping (orifice, threaded, slip-on, blind, weld neck, socket weld, lap-joint, and reducing) are available with a variety of facings, such as raised, flat, and ring-joint.

Flange connections tend to be expensive because they require the precision forming of metal. Factory-installed flanges must meet carefully measured dimensional specifications, and pipe segments cut to length on-site require skilled precision welding to attach flanges under more-difficult field conditions.

Manufacturers such as Victaulic and Grinnell produce sleeve-clamp fittings, which replace many flange connections. They attach to the end of a pipe segment via circumferential grooves pressed (or cut) around the end of the pipe to be joined. They are widely used on larger steel pipes and can also be used with other materials.

The chief advantage of these connectors is that they can be installed after cutting the pipe to length in the field. This can save time and considerable expense compared to flange connections, which must be factory- or field-welded to pipe segments. However, mechanically fastened joints are sensitive to residual and thickness stresses caused by dissimilar metals and temperature changes.

A grooved fitting, also known as a grooved coupling, has four elements: grooved pipe, gasket, coupling housing, and nuts and bolts. The groove is made by cold-forming (or machining) a groove at the end of a pipe. A gasket encompassed by coupling housing is wrapped around the two pipe ends, with the coupling engaging the groove; the bolts and nuts are tightened with a socket or impact wrench. The installed coupling housing encases the gasket and engages the grooves around the pipe to create a leakproof seal in a self-restrained pipe joint. There are two types of grooved coupling; a flexible coupling allows a limited amount of angular movement, and a rigid coupling does not allow movement and may be used where joint immobility is required (similar to a flange or welded joint).

 

Crimped or pressed connections to use special fittings permanently attached to tubing with a powered crimper. The fittings, manufactured with a pre-installed sealant or O-ring, slide over the tubing to be connected. High pressure is used to deform the fitting and compress the sealant against the inner tubing, creating a leakproof seal.^[31]

The advantages of this method are durability, speed, neatness, and safety. The connection can be made even when the tubing is wet. Crimped fittings are suitable for drinking water pipes and other hot-and-cold systems (including central heating). They are more expensive than sweated fittings.

Press fittings with either V and M profile (or contour) in stainless steel, carbon steel, and copper are trendy in Europe, and several manufacturers such as Viega, Geberit, Swiss Fittings, and ISOTUBI, distribute proprietary systems of press fittings. Compared to other connection types, press fittings have the advantages of installation speed and safety. Pressing a stainless steel fitting can be completed within five seconds with the correct equipment. Primary pressing of fittings to pipes or other fittings is performed using electrically powered press equipment, but mechanically driven press equipment is also available. Swiss Fittings is legally protected the German Brand "Pressfittings aus Edelstahl" in the USA. ^[32]

Press fittings of some major brands carry a plastic slip^{[clarification needed]} around the sleeves on each end of the fitting which falls off when the fitting has been compressed. This allows for a simple identification whether a press fitting has securely been installed.

Press fittings with appropriate and region-specific certification may be used for gas lines. Stainless steel and carbon steel press fittings can withstand up to 16 bars of pressure.

A disadvantage of press fittings is the dead space between the pipe and the fitting, which can possibly rule out use for beverage and food applications.

Types of Pressfittings
Connection Type	All Pressends	Pressend / Male Thread	Pressend / Female Thread	Valve Connection	Flange	End-Connector
	Elbow 90°, F/F & F/M Elbow 45°, F/F & F/M Bend 15°, 45°, 75° M/M Coupling Coupling Long Tee	Elbow 90° Male Coupling Bend 90° Male Thread Tee Male Union Male Coupling Male Straight Connector	Elbow 90° Female Coupling Double Tap Connector 90/90 with Female Thread Elbow 90° Female Adapter Coupling Female Straight Connector Adapter Female Coupling (ISO 228) Female Coupling Tee Female Union Female	3-PC HFF Ball Valve	Flange Coupling	Cap

Cast iron piping was traditionally made with one "spigot" end (plain, which was cut to length as needed) and one "socket" or "hub" end (cup-shaped). The larger-diameter hub was also called a "bell" because of its shape.

In use, the spigot of one segment was placed into the socket of the preceding one, and a ring of oakum was forced down into the joint with a caulking iron. Then the remainder of the space in the hub was filled up. Ideally, this would be done by pouring molten lead, allowing it to set, and hammering it tightly with a caulking tool. If this was not possible due to position or some other constraint, the joint could be filled with lead wool or rope, which was forcibly compacted one layer at a time.^[33]

This labor-intensive technique was durable if appropriately done but required time, skill, and patience for each joint to be made up. Quicker and lower-cost methods, such as rubber sleeve joints, have replaced mainly leaded hub connections of cast-iron piping in most new installations, but the older technology may still be used for some repairs.^{[21]: 149â€Å}  In addition, some conservative plumbing codes still require leaded hub joints for final connections where the sewer main leaves a building.

Cast iron DWV pipe and fittings are still used in premium construction because they muffle the sound of wastewater rushing through them,^{[21]: 149â€Å}  but today they are rarely joined with traditional lead joints.^{[21]: 149â€Å}  Instead, pipe and fittings with plain (non-belled) connections are butted against each other, and clamped with special rubber sleeve (or "no-hub") fittings.^{[18]: 71â€Å}  The rubber sleeves are typically secured with stainless steel worm drive clamping bands, which compress the rubber to make a tight seal around the pipes and fittings. These pipe clamps are similar to hose clamps, but are heavier-duty and ideally are made completely of stainless steel (including the screw) to provide maximum service life.^{[21]: 149 [18]: 71â€Å}  Optionally, the entire rubber sleeve may be jacketed with thin sheet metal, to provide extra stiffness, durability, and resistance to accidental penetration by a misplaced nail or screw.^{[21]: 149â€Å}  Although the fittings are not cheap, they are reasonably durable (the rubber is typically neoprene or flexible PVC).

An alternative design also allows the selective use of belled fittings made entirely of flexible rubber, including more-complex shapes such as wyes or tee-wyes.^{[18]: 69â€Å}  They are secured to cast iron pipe segments by use of stainless steel worm drive clamps. Because these fittings are not as stiff as traditional cast-iron fittings, the heavy pipe segments may need better anchoring and support to prevent unwanted movement.^{[21]: 150â€Å}  The lighter rubber fittings may not muffle sound as well as the heavy cast-iron fittings.

An advantage of flexible rubber fittings is that they can accommodate small misalignments and can be flexed slightly for installation in tight locations.^{[21]: 147, 149â€Å}  A flexible fitting may be preferred to connect a shower or heavy tub to the drainage system without transmitting slight movements or stresses, which could eventually cause cracking.^{[21]: 159â€Å}  Flexible fittings may also be used to reduce the transmission of vibration into the DWV system.

If necessary, clamped joints can be disassembled later, and the fittings and pipe may be reconfigured. However, it is often not customary to re-use the clamps and rubber sleeves, which their previous installation may deform and may not seal well after rearranging. Clamped fittings may occasionally need to be disassembled to provide access for "snaking" or "rodding-out" with a unique tool to clear blockage or clogs.^{[18]: 69â€Å}  This is also an indication that a clean-out fitting could be installed to provide easier future access.

• International Association of Plumbing and Mechanical Officials
• International Code Council
• the American Society for Testing and Materials

 

 

Plumbing originated during ancient civilizations, as they developed public baths and needed to provide potable water and wastewater removal for larger numbers of people.^[6]

The Mesopotamians introduced the world to clay sewer pipes around 4000 BCE, with the earliest examples found in the Temple of Bel at Nippur and at Eshnunna,^[7] used to remove wastewater from sites, and capture rainwater, in wells. The city of Uruk contains the oldest known examples of brick constructed Latrines, constructed atop interconnecting fired clay sewer pipes, c. 3200 BCE.^[8][9] Clay pipes were later used in the Hittite city of Hattusa.^[10] They had easily detachable and replaceable segments, and allowed for cleaning.

Standardized earthen plumbing pipes with broad flanges making use of asphalt for preventing leakages appeared in the urban settlements of the Indus Valley civilization by 2700 BC.^[11]

Copper piping appeared in Egypt by 2400 BCE, with the Pyramid of Sahure and adjoining temple complex at Abusir, found to be connected by a copper waste pipe.^[12]

The word "plumber" dates from the Roman Empire.^[13] The Latin for lead is plumbum. Roman roofs used lead in conduits and drain pipes^[14] and some were also covered with lead. Lead was also used for piping and for making baths.^[15]

Plumbing reached its early apex in ancient Rome, which saw the introduction of expansive systems of aqueducts, tile wastewater removal, and widespread use of lead pipes. The Romans used lead pipe inscriptions to prevent water theft. With the Fall of Rome both water supply and sanitation stagnated—or regressed—for well over 1,000 years. Improvement was very slow, with little effective progress made until the growth of modern densely populated cities in the 1800s. During this period, public health authorities began pressing for better waste disposal systems to be installed, to prevent or control epidemics of disease. Earlier, the waste disposal system had consisted of collecting waste and dumping it on the ground or into a river. Eventually the development of separate, underground water and sewage systems eliminated open sewage ditches and cesspools.

In post-classical Kilwa the wealthy enjoyed indoor plumbing in their stone homes.^[16][17]

Most large cities today pipe solid wastes to sewage treatment plants in order to separate and partially purify the water, before emptying into streams or other bodies of water. For potable water use, galvanized iron piping was commonplace in the United States from the late 1800s until around 1960. After that period, copper piping took over, first soft copper with flared fittings, then with rigid copper tubing using soldered fittings.

The use of lead for potable water declined sharply after World War II because of increased awareness of the dangers of lead poisoning. At this time, copper piping was introduced as a better and safer alternative to lead pipes.^[18]

The major categories of plumbing systems or subsystems are:^[19]

• potable cold and hot tap water supply
• plumbing drainage venting
• sewage systems and septic systems with or without hot water heat recycling and graywater recovery and treatment systems
• Rainwater, surface, and subsurface water drainage
• fuel gas piping
• hydronics, i.e. heating and cooling systems using water to transport thermal energy, as in district heating systems, like for example the New York City steam system.

A water pipe is a pipe or tube, frequently made of plastic or metal,^[a] that carries pressurized and treated fresh water to a building (as part of a municipal water system), as well as inside the building.

Lead was the favoured material for water pipes for many centuries because its malleability made it practical to work into the desired shape. Such use was so common that the word "plumbing" derives from plumbum, the Latin word for lead. This was a source of lead-related health problems in the years before the health hazards of ingesting lead were fully understood; among these were stillbirths and high rates of infant mortality. Lead water pipes were still widely used in the early 20th century and remain in many households. Lead-tin alloy solder was commonly used to join copper pipes, but modern practice uses tin-antimony alloy solder instead in order to eliminate lead hazards.^[20]

Despite the Romans' common use of lead pipes, their aqueducts rarely poisoned people. Unlike other parts of the world where lead pipes cause poisoning, the Roman water had so much calcium in it that a layer of plaque prevented the water contacting the lead itself. What often causes confusion is the large amount of evidence of widespread lead poisoning, particularly amongst those who would have had easy access to piped water,^[21] an unfortunate result of lead being used in cookware and as an additive to processed food and drink (for example as a preservative in wine).^[22] Roman lead pipe inscriptions provided information on the owner to prevent water theft.

Wooden pipes were used in London and elsewhere during the 16th and 17th centuries. The pipes were hollowed-out logs which were tapered at the end with a small hole in which the water would pass through.^[23] The multiple pipes were then sealed together with hot animal fat. Wooden pipes were used in Philadelphia,^[24] Boston, and Montreal in the 1800s. Built-up wooden tubes were widely used in the US during the 20th century. These pipes (used in place of corrugated iron or reinforced concrete pipes) were made of sections cut from short lengths of wood. Locking of adjacent rings with hardwood dowel pins produced a flexible structure. About 100,000 feet of these wooden pipes were installed during WW2 in drainage culverts, storm sewers and conduits, under highways and at army camps, naval stations, airfields and ordnance plants.

Cast iron and ductile iron pipe was long a lower-cost alternative to copper before the advent of durable plastic materials but special non-conductive fittings must be used where transitions are to be made to other metallic pipes (except for terminal fittings) in order to avoid corrosion owing to electrochemical reactions between dissimilar metals (see galvanic cell).^[25]

Bronze fittings and short pipe segments are commonly used in combination with various materials.^[26]

The difference between pipes and tubes is a matter of sizing. For instance, PVC pipe for plumbing applications and galvanized steel pipe are measured in iron pipe size (IPS). Copper tube, CPVC, PeX and other tubing is measured nominally, basically an average diameter. These sizing schemes allow for universal adaptation of transitional fittings. For instance, 1/2" PeX tubing is the same size as 1/2" copper tubing. 1/2" PVC on the other hand is not the same size as 1/2" tubing, and therefore requires either a threaded male or female adapter to connect them. When used in agricultural irrigation, the singular form "pipe" is often used as a plural.^[27]

Pipe is available in rigid joints, which come in various lengths depending on the material. Tubing, in particular copper, comes in rigid hard tempered joints or soft tempered (annealed) rolls. PeX and CPVC tubing also comes in rigid joints or flexible rolls. The temper of the copper, whether it is a rigid joint or flexible roll, does not affect the sizing.^[27]

The thicknesses of the water pipe and tube walls can vary. Because piping and tubing are commodities, having a greater wall thickness implies higher initial cost. Thicker walled pipe generally implies greater durability and higher pressure tolerances. Pipe wall thickness is denoted by various schedules or for large bore polyethylene pipe in the UK by the Standard Dimension Ratio (SDR), defined as the ratio of the pipe diameter to its wall thickness. Pipe wall thickness increases with schedule, and is available in schedules 20, 40, 80, and higher in special cases. The schedule is largely determined by the operating pressure of the system, with higher pressures commanding greater thickness. Copper tubing is available in four wall thicknesses: type DWV (thinnest wall; only allowed as drain pipe per UPC), type 'M' (thin; typically only allowed as drain pipe by IPC code), type 'L' (thicker, standard duty for water lines and water service), and type 'K' (thickest, typically used underground between the main and the meter).

Wall thickness does not affect pipe or tubing size.^[28] 1/2" L copper has the same outer diameter as 1/2" K or M copper. The same applies to pipe schedules. As a result, a slight increase in pressure losses is realized due to a decrease in flowpath as wall thickness is increased. In other words, 1 foot of 1/2" L copper has slightly less volume than 1 foot of 1/2 M copper.^[29]

Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead, bamboo, wood, or stone. Hollowed wooden logs wrapped in steel banding were used for plumbing pipes, particularly water mains. Logs were used for water distribution in England close to 500 years ago. US cities began using hollowed logs in the late 1700s through the 1800s. Today, most plumbing supply pipe is made out of steel, copper, and plastic; most waste (also known as "soil")^[30] out of steel, copper, plastic, and cast iron.^[30]

The straight sections of plumbing systems are called "pipes" or "tubes". A pipe is typically formed via casting or welding, whereas a tube is made through extrusion. Pipe normally has thicker walls and may be threaded or welded, while tubing is thinner-walled and requires special joining techniques such as brazing, compression fitting, crimping, or for plastics, solvent welding. These joining techniques are discussed in more detail in the piping and plumbing fittings article.

Galvanized steel potable water supply and distribution pipes are commonly found with nominal pipe sizes from 3⁄8 inch (9.5 mm) to 2 inches (51 mm). It is rarely used today for new construction residential plumbing. Steel pipe has National Pipe Thread (NPT) standard tapered male threads, which connect with female tapered threads on elbows, tees, couplers, valves, and other fittings. Galvanized steel (often known simply as "galv" or "iron" in the plumbing trade) is relatively expensive, and difficult to work with due to weight and requirement of a pipe threader. It remains in common use for repair of existing "galv" systems and to satisfy building code non-combustibility requirements typically found in hotels, apartment buildings and other commercial applications. It is also extremely durable and resistant to mechanical abuse. Black lacquered steel pipe is the most widely used pipe material for fire sprinklers and natural gas.

Most typical single family home systems will not require supply piping larger than

3⁄4 inch (19 mm) due to expense as well as steel piping's tendency to become obstructed from internal rusting and mineral deposits forming on the inside of the pipe over time once the internal galvanizing zinc coating has degraded. In potable water distribution service, galvanized steel pipe has a service life of about 30 to 50 years, although it is not uncommon for it to be less in geographic areas with corrosive water contaminants.

Copper pipe and tubing was widely used for domestic water systems in the latter half of the twentieth century. Demand for copper products has fallen due to the dramatic increase in the price of copper, resulting in increased demand for alternative products including PEX and stainless steel.

Plastic pipe is in wide use for domestic water supply and drain-waste-vent (DWV) pipe. Principal types include: Polyvinyl chloride (PVC) was produced experimentally in the 19th century but did not become practical to manufacture until 1926, when Waldo Semon of BF Goodrich Co. developed a method to plasticize PVC, making it easier to process. PVC pipe began to be manufactured in the 1940s and was in wide use for Drain-Waste-Vent piping during the reconstruction of Germany and Japan following WWII. In the 1950s, plastics manufacturers in Western Europe and Japan began producing acrylonitrile butadiene styrene (ABS) pipe. The method for producing cross-linked polyethylene (PEX) was also developed in the 1950s. Plastic supply pipes have become increasingly common, with a variety of materials and fittings employed.

• PVC/CPVC – rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC stands for polyvinyl chloride, and it has become a common replacement for metal piping. PVC should be used only for cold water, or for venting. CPVC can be used for hot and cold potable water supply. Connections are made with primers and solvent cements as required by code.^[31]
• PP – The material is used primarily in housewares, food packaging, and clinical equipment,^[32] but since the early 1970s has seen increasing use worldwide for both domestic hot and cold water. PP pipes are heat fused, being unsuitable for the use of glues, solvents, or mechanical fittings. PP pipe is often used in green building projects.^[33]
• PBT – flexible (usually gray or black) plastic pipe which is attached to barbed fittings and secured in place with a copper crimp ring. The primary manufacturer of PBT tubing and fittings was driven into bankruptcy by a class-action lawsuit over failures of this system.^{[citation needed]} However, PB and PBT tubing has since returned to the market and codes, typically first for "exposed locations" such as risers.
• PEX – cross-linked polyethylene system with mechanically joined fittings employing barbs, and crimped steel or copper rings.
• Polytanks – plastic polyethylene cisterns, underground water tanks, above ground water tanks, are usually made of linear polyethylene suitable as a potable water storage tank, provided in white, black or green.
• Aqua – known as PEX-Al-PEX, for its PEX/aluminum sandwich, consisting of aluminum pipe sandwiched between layers of PEX, and connected with modified brass compression fittings. In 2005, many of these fittings were recalled.^{[further explanation needed]}

Present-day water-supply systems use a network of high-pressure pumps, and pipes in buildings are now made of copper,^[34] brass, plastic (particularly cross-linked polyethylene called PEX, which is estimated to be used in 60% of single-family homes^[35]), or other nontoxic material. Due to its toxicity, most cities moved away from lead water-supply piping by the 1920s in the United States,^[36] although lead pipes were approved by national plumbing codes into the 1980s,^[37] and lead was used in plumbing solder for drinking water until it was banned in 1986.^[36] Drain and vent lines are made of plastic, steel, cast iron, or lead.^[38][39]

• 
  Monument to water pipe in Mytishchi (Russia)
• 
  A specific water pipe made for use with pressure vessels. The pipe can sustain high-pressure water and is relatively small.
• 
  Concrete water pipe
• 
  Connecting to an existing water line (white pipe) with a stainless steel tapping sleeve and valve (red). A concrete thrust block is being formed behind the new connection.
• 
  Water pipe connected to the septic tank.
• 
  Sewer pipe

In addition to lengths of pipe or tubing, pipe fittings such as valves, elbows, tees, and unions. are used in plumbing systems.^[40] Pipe and fittings are held in place with pipe hangers and strapping.

Plumbing fixtures are exchangeable devices that use water and can be connected to a building's plumbing system. They are considered to be "fixtures", in that they are semi-permanent parts of buildings, not usually owned or maintained separately. Plumbing fixtures are seen by and designed for the end-users. Some examples of fixtures include water closets^[41] (also known as toilets), urinals, bidets, showers, bathtubs, utility and kitchen sinks, drinking fountains, ice makers, humidifiers, air washers, fountains, and eye wash stations.

Threaded pipe joints are sealed with thread seal tape or pipe dope. Many plumbing fixtures are sealed to their mounting surfaces with plumber's putty.^[42]

Plumbing equipment includes devices often behind walls or in utility spaces which are not seen by the general public. It includes water meters, pumps, expansion tanks, back flow preventers, water filters, UV sterilization lights, water softeners, water heaters, heat exchangers, gauges, and control systems.

There are many tools a plumber needs to do a good plumbing job. While many simple plumbing tasks can be completed with a few common hand held tools, other more complex jobs require specialised tools, designed specifically to make the job easier.

Specialized plumbing tools include pipe wrenches, flaring pliers, pipe vise, pipe bending machine, pipe cutter, dies, and joining tools such as soldering torches and crimp tools. New tools have been developed to help plumbers fix problems more efficiently. For example, plumbers use video cameras for inspections of hidden leaks or other problems; they also use hydro jets, and high pressure hydraulic pumps connected to steel cables for trench-less sewer line replacement.

Flooding from excessive rain or clogged sewers may require specialized equipment, such as a heavy duty pumper truck designed to vacuum raw sewage.^{[citation needed]}

Bacteria have been shown to live in "premises plumbing systems". The latter refers to the "pipes and fixtures within a building that transport water to taps after it is delivered by the utility".^[43] Community water systems have been known for centuries to spread waterborne diseases like typhoid and cholera. However, "opportunistic premises plumbing pathogens" have been recognized only more recently: Legionella pneumophila, discovered in 1976, Mycobacterium avium, and Pseudomonas aeruginosa are the most commonly tracked bacteria, which people with depressed immunity can inhale or ingest and may become infected with.^[44] Some of the locations where these opportunistic pathogens can grow include faucets, shower heads, water heaters and along pipe walls. Reasons that favor their growth are "high surface-to-volume ratio, intermittent stagnation, low disinfectant residual, and warming cycles". A high surface-to-volume ratio, i.e. a relatively large surface area allows the bacteria to form a biofilm, which protects them from disinfection.^[44]

Much of the plumbing work in populated areas is regulated by government or quasi-government agencies due to the direct impact on the public's health, safety, and welfare. Plumbing installation and repair work on residences and other buildings generally must be done according to plumbing and building codes to protect the inhabitants of the buildings and to ensure safe, quality construction to future buyers. If permits are required for work, plumbing contractors typically secure them from the authorities on behalf of home or building owners.^{[citation needed]}

In Australia, the national governing body for plumbing regulation is the Australian Building Codes Board. They are responsible for the creation of the National Construction Code (NCC), Volume 3 of which, the Plumbing Regulations 2008^[45] and the Plumbing Code of Australia,^[46] pertains to plumbing.

Each Government at the state level has their own Authority and regulations in place for licensing plumbers. They are also responsible for the interpretation, administration and enforcement of the regulations outlined in the NCC.^[47] These Authorities are usually established for the sole purpose of regulating plumbing activities in their respective states/territories. However, several state level regulation acts are quite outdated, with some still operating on local policies introduced more than a decade ago. This has led to an increase in plumbing regulatory issues not covered under current policy, and as such, many policies are currently being updated to cover these more modern issues. The updates include changed to the minimum experience and training requirements for licensing, additional work standards for new and more specific kinds of plumbing, as well as adopting the Plumbing Code of Australia into state regulations in an effort to standardise plumbing regulations across the country.

In Norway, new domestic plumbing installed since 1997 has had to satisfy the requirement that it should be easily accessible for replacement after installation.^[48] This has led to the development of the pipe-in-pipe system as a de facto requirement for domestic plumbing.

In the United Kingdom the professional body is the Chartered Institute of Plumbing and Heating Engineering (educational charity status) and it is true that the trade still remains virtually ungoverned;^[49] there are no systems in place to monitor or control the activities of unqualified plumbers or those home owners who choose to undertake installation and maintenance works themselves, despite the health and safety issues which arise from such works when they are undertaken incorrectly; see Health Aspects of Plumbing (HAP) published jointly by the World Health Organization (WHO) and the World Plumbing Council (WPC).^[50][51] WPC has subsequently appointed a representative to the World Health Organization to take forward various projects related to Health Aspects of Plumbing.^[52]

In the United States, plumbing codes and licensing are generally controlled by state and local governments. At the national level, the Environmental Protection Agency has set guidelines about what constitutes lead-free plumbing fittings and pipes, in order to comply with the Safe Drinking Water Act.^[53]

Some widely used Standards in the United States are:^{[citation needed]}

• ASME A112.6.3 – Floor and Trench Drains
• ASME A112.6.4 – Roof, Deck, and Balcony Drains
• ASME A112.18.1/CSA B125.1 – Plumbing Supply Fittings
• ASME A112.19.1/CSA B45.2 – Enameled Cast Iron and Enameled Steel Plumbing Fixtures
• ASME A112.19.2/CSA B45.1 – Ceramic Plumbing Fixtures

In Canada, plumbing is a regulated trade requiring specific technical training and certification. Standards and regulations for plumbing are overseen at the provincial and territorial level, each having its distinct governing body:

• Governing Bodies: Each province or territory possesses its regulatory authority overseeing the licensing and regulation of plumbers. For instance, in Ontario, the Ontario College of Trades handles the certification and regulation of tradespeople, whereas in British Columbia, the Industry Training Authority (ITA) undertakes this function.

• Certification: To achieve certified plumber status in Canada, individuals typically complete an apprenticeship program encompassing both classroom instruction and hands-on experience. Upon completion, candidates undergo an examination for their certification.

• Building Codes: Plumbing installations and repairs must adhere to building codes specified by individual provinces or territories. The National Building Code of Canada acts as a model code, with provinces and territories having the discretion to adopt or modify to their specific needs.

• Safety and Health: Given its direct correlation with health and sanitation, plumbing work is of paramount importance in Canada. Regulations ensure uncontaminated drinking water and proper wastewater treatment, underscoring the vital role of certified plumbers for public health.

• Environmental Considerations: Reflecting Canada's commitment to environmental conservation, there is an increasing emphasis on sustainable plumbing practices. Regulations advocate water conservation and the deployment of eco-friendly materials.

• Standards: The Canadian Standards Association (CSA) determines standards for diverse plumbing products, ensuring their safety, quality, and efficiency. Items such as faucets and toilets frequently come with a CSA certification, indicating adherence to required standards.^[54]

• Teresi, Dick (2002). Lost Discoveries: The Ancient Roots of Modern Science--from the Babylonians to the Maya. New York: Simon & Schuster. pp. 351–352. ISBN 0-684-83718-8.

• Lead Water Pipes and Infant Mortality in Turn-of-the-Century Massachusetts

Agency for Toxic Substances and Disease Registry:

• ATSDR Case Studies in Environmental Medicine: Lead Toxicity
• Case Studies in Environmental Medicine—Lead Toxicity
• ToxFAQs: Lead

[[Category:Bathrooms]