Plumbing Glossary

Plumbing glossary is an alphabetical list of terms used in the plumbing field with the definitions for those terms. Every industry and trade has its own standards and terminologies. This plumbing glossary is our attempt to help the general public understand some of the terms unique to plumbing industry. Click on a letter below to jump to the definition you need.




ABS - Acrylonitrile Butadiene Styrene: A rigid black plastic pipe used for Drain, waste, and vent lines.

Aerator : A device screwed into the end of a faucet spout that mixes air into flowing water, and controls flow to reduce splashing. It sometimes contains a baffle to reduce flow to 2.5 gpm.

Air Lock : Blockage in the flow of liquid, esp. on the suction side of a pump caused by an air bubble in the line.

Anti-Siphon : Preventive device for the backflow of liquid into a system. Used on sprinkler systems to prevent water from trickling back into the supply that is feeding it.

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BTU : British Thermal Unit - A unit of heat energy required to raise the temperature of 1 lb. of water 1 degree Fahrenheit.

Back Flow Preventer : A device to prevent water from traveling from one system back into any part of the main distribution system, usually by siphoning, esp. into a potable water supply. This is generally required for sprinkler systems, handheld showers, pullout faucet spouts, kitchen sprayers, etc.

Back Pressure : Pressure that resists the flow of fluid in a piping system.

Backwater Valve : Sewer line valve that prevents sewage from flowing back into the house.

Ball Check Valve : A valve that uses a ball to seal against a seat to stop flow in one direction.

Basin Wrench : A wrench with a long handle with jaws mounted on a swivel that allows the jaws to reach and handle nuts to fasten faucets to a previously installed sink.

Branch : Any part of a drain system other than the main, riser, or stack.

Branch Vent : A vent connecting one or more individual vents with a vent stack.

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Catch Basin : Large underground container, with a grate on the top, for collection of storm water run-off. It catches or collects dirt and other debris and prevents them from polluting streams and lakes.

Centerset : Style of bathroom faucet having combined spout and handles, with handles 4 inches apart, center-to-center. Also a single-handle faucet installed on 4 inches center-to-center faucet holes.

Check Valve : A type of backflow preventer installed in a pipe run that allows water to flow in only one direction.

Circuit Vent : Plumbing drainage system vertical vent which is run from the last two traps on a horizontal drain line to the main vent stack of a building drainage system.

Cistern : Rainwater storage tank, often underground.

Cleanout Plug : A plug in a trap or drain pipe that provides access for the purpose of clearing an obstruction.

Closet : Toilet.

Closet Auger : A flexible rod with a curved end used to access the toilet's built-in trap and remove clogs.

Closet Bend : A curved fitting mounted immediately below the toilet that connects the closet flange to the toilet drain.

Closet Flange : An anchoring ring that attaches to the closet bend and secured to the floor. The heads of closet bolts, used to secure the toilet in place, insert into slots in the closet flange.

Cock : A faucet or valve for regulating the flow of water.

Common Vent : Building drain system vertical vent which connects two or more fixture branches on the same level.

Compression Valve : A type of valve that is often used for water faucets. It is opened or closed by raising or lowering a horizontal disk by a threaded stem.

Coupling : Vent pipe hood, which protects it from the elements.

Culvert : A pipe-like construction of concrete that passes under a road to allow drainage.

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plumbing glossary


Desanco Fitting : A type of compression adapter that connects tubular brass fittings to PVC pipe.

Dip Tube : Tube inside the water heater that sends cold water to the bottom of the tank.

Direct Tap : Clamping device that allows a branch line to be drilled and tapped off a main line.

Discharge Tube : Outlet tube that connects a disposer or sump pump to the drain line.

Dishwasher Tailpiece : A flanged adapter connecting a basket strainer to the drainpipe with a dishwasher inlet.

Diverter : Valves which direct water to various outlets. They are used in showers, tubs, bidets, and sinks.

Drip Leg : A stub end pipe placed at a low point in the gas piping to collect condensate and permit its removal.

Drum Trap : An obsolete, non-vented drain lead or cast iron canister trap formerly used in sewer lines.

Duo Valve : A twin valve (hot & cold) with a single on/off lever used for washing machine boxes.

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E. Coli : The common abbreviation of Escherichia Coli. One of the members of the coliform groups of bacteria indicating fecal contamination.

Earthquake Strap : A metal strap used to secure a water heater to the house frame or foundation.

Efficiency : A product's ability to utilize input energy, expressed as a percentage.

Effluent : Septic system liquid waste.

Expansion Tank : A tank designed to absorb excess pressure due to thermal expansion (e.g. closed system).

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Fall/Flow : The proper slope or pitch of a pipe for adequate drainage.

Female Fitting : A fitting that receives a pipe or fitting. A fitting into which another fitting is inserted.

Finish Plumbing : Installation of plumbing fixtures to make the system usable.

Flapper Valve : The part on the bottom of the toilet tank that opens to allow water to flow from the tank into the bowl.

Float Ball : The floating ball connected to the ballcock inside the tank that rises or falls with changing water levels in the tank, and actuates or shuts off the ballcock as needed.

Floor Flange : A fitting that connects a toilet to a floor drain.

Flushometer : Toilet valve that automatically shuts off after it meters a certain amount of water flow.

Flux : Paste applied to copper pipes and fittings before soldering to help the fusion process and prevent oxidation.

Footprint : The area of floor space taken up by a water heater or other appliance.

French Drain : A covered ditch containing a layer of fitted or loose stone or other pervious material.

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Gas Cock : Plug valve installed the main gas line and an appliance.

Gas Control : Device used to regulate gas pressure on a water heater.

Gate : A device that controls the flow in a conduit, pipe, or tunnel.

Gate Diverter : The pop-up lever on a tub faucet that activates the diverter valve.

Gravity Operated Toilet : A toilet that relies on the natural downward pressure of water in a toilet tank to flush the toilet effectively.

Gray Water : Waste water from sinks, showers, and bathtubs, but not toilets.

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Horizontal Branch : Lateral drain pipes that run from plumbing fixtures to the waste stack in a building or in the soil.

Horizontal Run : The horizontal distance between the point where fluid enters a pipe and the point at which it leaves.

Hose Bibb : An outdoor faucet, also used to supply washing machines.

House Trap : U-shaped fitting with two adjacent cleanout plugs visible at floor level if main drain runs under floor.

Hubless (No-Hub) : Cast iron drainage pipe with neoprene gaskets and clamps.

Hydronic : System of forced hot water.

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Indirect Wastes : Waste pipe used to convey gray water by discharging it into a plumbing fixture such as a floor drain.

Instantaneous Water Heater : A type of water heater that heats water as it flows through a heat exchanger coil.

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Jet : An orifice or other feature of a toilet that is designed to direct water into the trapway quickly to start the siphon action.

Johnni-bolts : Closet bolts, used to mount toilet bowls to the closet flange.

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Knockout Plug : PVC test plug.

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Lavatory (Lav) : A fixed bowl or basin with running water and drainage for washing. Bathroom sink.

Leach Field : Porous soil area, through which septic tank leach lines run, emptying the treated waste.

Leader : Pipe carrying rainwater to the ground or sewer.

Lock Nut : Nut fitted into a piece of pipe and screwed onto another pipe to join the two pieces

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Main : The primary artery of supply of the water supply or drain system in which all the branches connect. In the case of drains, known as the Main Vent.

Male Threads : Threads on the outside of pipes and fittings.

Malleable Fittings : Fittings made of metal which is soft and pliable.

Manifold : A fitting that connects a number of branches to the main; serves as a distribution point.

Mechanicals : The wiring, plumbing and heating and cooling systems in a building; also the components with moving parts such as furnaces, plumbing fixtures, etc.

Multi-Stage Pump : A pump that has more than one impeller.

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plumbing glossary


Nipple : A short length of pipe installed between couplings or other fittings.

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O-Ring : Round rubber washer used to create a watertight seal, chiefly around valve stems.

Oakum : Loosely woven hemp rope that has been treated with oil or other waterproofing agent; it is used to caulk joints in a bell and spigot pipe and fittings.

Outlet Sewer : Pipe section in a septic system which runs between the septic tank and the drainage field.

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PVC : Polyvinyl chloride. A rigid white or cream-colored plastic pipe used in non-pressure systems, such as drainage, waste, and vent systems.

Packing : Fibrous material that is used on faucets to prevent leaks.

Packing Nut : Nut that holds the stem of a faucet in position & holds the packing material.

Peak Hour Demand : Time when the largest demand for hot water is needed.

Pipe Dope : Slang for pipe-joint compound. Substance applied to threaded fittings to create a watertight seal.

Pitch : Downward slope of a drain pipe in the direction of the water flow.

Plumb : Precisely vertical. Also to test for, or to make vertical. Also to perform plumbing work.

Plumber's Putty : Pliable, popular putty used to seal joints between drain pieces and fixture surfaces.

Plumbing Tree : Prefabricated set of drain waste, vent, and supply lines

Pressure Balance Valve : Shower mixing valve that automatically maintains balance between incoming hot and cold water supplies by immediately regulating fluctuations in pressure. As a result, temperature remains constant, though the outlet pressure may drop. Also known as an anti-scald valve.

Pressure Tank : Device used to pump water from a well.

Pressure Tubing : Tubing used to conduct fluids under pressure or at elevated temperatures or both, and produced to stricter tolerances than pipe.

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Rated Storage Volume : Quantity of water stored in a tank.

Reamer : A grinding tool used to level or remove burrs from valve seats in faucets so that the valve stem will fit properly.

Recovery Capacity : The amount of water in gallons per hour raised 100 degrees F at a given thermal efficiency and BTU per hour input.

Reducer : A fitting that connects pipes of different sizes together.

Return Circulation System : Tempered water from or near the point of usage which eliminates waste of hot water used for long runs and adds storage to the system.

Revent : Pipe installed specifically to vent a fixture trap. Connects with the vent system above the fixture.

Reverse Trap Water Closet : A water closet having a siphonic trapway at the rear of the bowl, and integral flushing rim and jet.

Rigid Pipe : Pipe designed to transmit the backfill load to the foundation beneath the pipe. Rigid pipe must be supported on the bottom portion of the pipe.

Roof Flashing : Sheet metal installed at any break in a shingled roofline to prevent leaks. Also around sewer vents, fluepipes.

Rough-In : Installation of the drain, waste, vent, and supply lines in a structure to the proposed location of each fixture.

Rough-In Dimensions : The distance from a finished wall or floor to the center of the waste or supply opening or mounting holes on a plumbing fixture.

Run : A complete or secondary section of pipe that extends from supply to fixture or drain to stack.

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Sanitary Sewer : House drain that carries wastewater away from the house to a sewer system or septic tank.

Self-Rimming Sink : Sink with no metal ring that has a built-in lip of the same material which supports it in the vanity top.

Service Entrance : Pipe connecting the water company piping to the water meter.

Setting : Pumps' vertical distance in feet from the top of the well to the top of the pump.

Shroud : Color-matched component under a wall-mount lavatory that covers the drain outlet for aesthetic purposes.

Sleeve : Pipe which is passed through a wall for the purpose of inserting another pipe through it.

Slip Joint : A connection made with compression fittings.

Soil Stack : Largest vertical drain line to which all branch waste lines connect. This line carries waste to the sewer line.

Solder : Metal alloy that is melted to create a fused joint between metal pieces. Also the act of melting solder into the joint.

Spud : A threaded opening on the water heater tank. Also a tool for digging having characteristics of a shade and chisel.

Stack : The vertical main in the drain, waste, and vent system, extending one or more stories.

Static Lift : The vertical distance between source and discharge water levels in a pump installation.

Stop Valve : The shutoff valve under sinks and toilets. Allows water supply to be cut off to one fixture without affecting the water supply to other fixtures.

Straight Cross : Fitting that connects four pipes of the same diameter.

Sump : A pit or pool for draining, collecting, or storing water. A chamber which provides water to the pump.

Sweating : Slang term for soldering. Also formation of condensation on the outside of pipes or toilet tanks.

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T & P Valve : Temperature & pressure relief valve. A safety device used to expel excess pressure or heat from inside a tank.

Tailpiece : Section of pipe that runs between a fixture outlet and the trap.

Tail Pipe : The pipe added below the jet assembly, in a weak well application.

Tap Tee : Cast iron tee with a threaded female side inlet.

Thermocouple : Small electric generator. Electron flow between the hot junction of 1200 degrees F and cold junction of 600 degrees F creates millivoltage.

Trap : Curved section of drain line that prevents sewer odors from escaping into the atmosphere. All fixtures that have drains must have a "P" trap installed. A toilet is the only plumbing fixture with an "S" trap.

Trap Arm : The waste arm portion of a drainage trap.

Trap Dip : The U-bend portion of a drainage trap.

Trap Seal : Height of water in a toilet bowl "at rest.". It provides the water seal which prevents sewer gases from entering the home. It is measured from the top of the dam down to the inlet of the trapway. Also referred to as deep seal.

Trip Lever : Flush handle and actuating arm on a toilet tank. Also the lever that opens and closes the drain on the bathtub waste and overflow.

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Uni-flex : One piece stop and riser combination. One-piece supply.

Union : Three piece fitting that joins two sections of pipe, but allows them to be disconnected without cutting the pipe. Used primarily with steel pipe; never in a DWV system.

Usable Storage : Percentage of hot water that can be drawn from a tank before the temperature drops to a point that it is no longer considered hot.

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plumbing glossary


Vacuum Breaker : An anti-siphon device that prevents the backflow of contaminated water into the water supply system.

Valve Dressing : Resurfacing a worn valve seat with a special tool. Stops leaks by providing a smooth sealing surface. Applies only to older compression style faucets.

Valve Seat : The non-moving part of a valve. Water flow is stopped when the moveable portion of the valve comes in contact with the valve seat.

Vent : A pipe that allows air into a drain system to balance the air pressure, preventing water in the traps from being siphoned off.

Viscosity : The resistance of fluids to flow, due to internal forces and friction between molecules, which increases as its temperature decreases.

Vitreous China : Ceramic materials fired at high temperature to form a non-porous body, having exposed surfaces coated with ceramic glaze fused to the body. This is used to form bathroom fixtures such as toilets, bidets, and lavs.

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Washdown Water Closet : Water closet having a siphon trapway at the front of the bowl, and integral flushing rim.

Waste Arm : Drain extension pipe, usually to extend a sink drain into a wall.

Waste & Overflow : Drain assembly for a bathtub. The outlet at the top removes the overflow water during tub filling and the drain at the bottom removes wastewater when the tub is drained.

Widespread : A style of bathroom lavatory faucet having separate spout and handles, usually 8" from center of handle to handle.

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Yoke : Usually a brass casting that holds both the hot and cold valves and the mixing chamber for the water. May also refer to an assembly of copper or other metal which serves the same function.

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