Plumbing Glossary | Terms & Definitions

Plumbing Glossary | Terms & Definitions

May 25, 2018


Words in one field can mean something entirely different in another field.

For instance, “bleed” to most people refers to blood. To plumbers, bleed means to drain a pipe of excess air.

Male, female, snake, rim, trap… you may think you know what these words mean, but to a plumber, they carry a whole different set of meanings.

Learn the plumber’s language by reading the plumbing glossary.

Plumbing Glossary

ABS (acrylonitrile-butadiene-styrene) – A type of rigid plastic drainage pipe.

Aerator – A woven, sieve-like screen attached to the end of a spigot that adds oxygen to the water.

Air chamber (aka air cushion or water hammer arrester) – A device added to supply pipes to prevent water hammer.

Air gap – 1) The unobstructed vertical distance between the opening of a pipe or fixture (such as a tub) and the overflow rim of the receptacle where the water is flowing. 2) A capped pipe (backflow protection) that prevents sink drain water from backing up into the dishwasher.

Angle valve – Valve with a 90-degree bend, eliminating the need for an elbow.

Antisiphon valve – Device installed on supply line to prevent the siphoning of contaminated water into the potable drinking supply.

Auger – see Snake.

Back venting – Vent pipe that loops up from fixture and connects with the vent stack or secondary vent at higher level (see Vent stack).

Ball cock – The assembly inside of a tank that uses a float or similar device to control the flow of water into the tank, such as inside your toilet tank.

Ball float – see Float ball.

Bidet – A French loan word for a bathroom fixture designed for washing the perineal area. Plumbing for bidets is much simpler than for toilets, only requiring a sink-type trap and drainpipe.

Bleed – The process of draining a pipe of excess air by opening a valve, such as with a radiator.

Boiler – A system that uses hot water or low pressure steam for heating or power. Also, a storage tank for hot water.

Building trap – see House trap.

Cap – A pipe fitting with a solid end used to close off a pipe.

Center-to-Center – When mounting faucets, it’s the distance between the centers of the holes on a sink deck. In pipefitting, it’s the distance between the centers of two fittings in a run.

Cleanout – A drainage system opening that provides plumbers access to the drainline or trap under a sink, typically used for the removal of obstructions. Cleanouts can be a removable plug or cap, or a removable fixture or fixture trap.

Code – A shorthand way of referring to the Uniform Plumbing Code and the legal requirements for the installation and inspection of plumbing systems.

Coupling – A pipe fitting that connects two lengths of pipe in a straight run.

CPVC (chlorinated polyvinyl chloride) – Type of plastic pipe used for hot water.

Cross Connection – An accidental connection between two otherwise separate plumbing systems, one of which contains potable water. The other piping system, whatever it is, contaminates the potable water supply.

Drain – Any pipe that transfers waste water into a drainage system.

DWV (drain-waste-vent) – The plumbing system that carries waste water and waste, allows sewer gases to safely escape, and maintains atmospheric pressure within the pipes.

Elbow – A plumbing fitting used to make sharp turns in pipe runs. Normally a 90-degree elbow is used to make a right-angle turn. A street elbow has one male end and one female end.

Escutcheon – A decorative flange piece that fits over a pipe or faucet coming out of a wall.

Faucet – The valve end of a water pipe where water is drawn or flows from.

Female – Any pipe, valve, or fitting with internal threads.

Flange – A flat fitting or integral edging with holes used to form a tight connection, for instance a toilet bowl bolted to a floor flange.

Flapper – Device that fits over the valve opening at the bottom of your toilet tank that opens when you flush, allowing water to flow from the tank to the bowl.

Float arm – The metal arm that connects the float to the ball cock assembly.

Float ball – A large ball, usually made of plastic, that floats on the surface of the water in the toilet tank. It rises and falls with the water level. When it reaches a certain height, the water supply is turned off.

Flue – A large pipe that safely vents combustion gases, excess air, ad fumes from gas-powered appliances, such as furnaces and gas water heaters.

Gasket – A device, usually rubber, used to form a watertight seal around two valve parts.

Gate valve – The most common type of plumbing valve, which acts as a gate to fully open or close the flow of water. Gate valve are normally used for isolation valve where only fully closed or fully opened is needed.

Globe valve – A valve with a washer at the end of the stem that fits into the valve seat to stop of control the flow of water. Globe valves are used to regulate water flow.

House trap – U-shaped fitting with two adjacent cleanout plugs. If the main drain runs under the floor, it should be visible at floor level.

Indirect venting – Plumbing fixture is vented (and drained) into floor drain or laundry tub.

Individual venting – Fixture or fixture group has its own vent to the roof.

J-bend – A piece of drainpipe in the shape of a J, used with an elbow in traps.

Joint – The point here two sections of pipe are fitting together.

Locknut – A type of nut that fits onto one piece of pipe to connect it to another piece.

Male – Any pipe, valve, or fitting with external threads.

Nipple – a short length of galvanized pipe with external threads on both sides for joining fittings.

O-ring – A narrow rubber ring used around some faucets to prevent leaking around the stem or base.

Packing nut – A nut screwed down onto the faucet stem to hold the packing tight.

PB (polybutylene) – Flexible plastic piping used for hot or cold water.

PE (polyethylene) – Flexible plastic tubing for cold water.

Pipe cutter – A sharp tool used to make perfectly straight cuts.

Plug – A closed-off, male fitting to close off female pipe ends with internal threads.

PP (polypropylene) – Type of rigid plastic used for traps and drainpipes.

P-trap – A P-shaped fixture trap. Water gets trapped in the bend to create a seal, preventing sewer gases from rising through the drain.

PVC (polyvinyl chloride) – A popular rigid type of plastic piping for cold water.

Reamer – A tool that fits into pipe ends to grind any internal burrs formed after pipe cutting. It is often sold with pipe cutters.

Riser – A vertical run of pipe.

Relief valve – A safety valve used to relieve either pressure, temperature, or a vacuum automatically. A temperature and pressure relief valve lets excess water and steam escape from the water heater.

Safety shutoff device – A safety device that automatically shuts off the gas supply in the event that the igniter fails.

Seat – The part of the valve where the washer, stem, or piece fits, stopping the flow of water.

Sludge – The solid-ish waste matter that falls and collects at the bottom of a septic tank.

Snake – A metal, spring-like tool used to break up drain clogs and blockages.

Solder – Soft metal (tin and lead) used to join copper piping.

Stopper – see Flapper.

Sweating – Term used to describe droplets and moisture accumulation on pipes, tanks, and other cold surfaces, caused by condensation when humid air meets a cold surface.

Tempering valve – A valve that mixes some cold water with hot water to prevent a sweating tank.

Threader – Tool used to cut threads into a pipe.

Toggle bolt – A bolt with two hinged wings, used for fastening brackets and sometimes to repair small leaks in water tanks.

Trap – A section of pipe, normally a P-trap, used to hold a water seal to prevent sewer gases from rising through the drain opening.

Union – A fitting that joins two sections of pipe, allowing assembly and disassembly without having to take the section apart.

Valve – Device that controls the flow of water.

Valve seat – see Seat.

Valve seat wrench – A hexagonal wrench used for inserting or removing a valve seat.

Vent – A system for releasing flue gases to the outside atmosphere.

Water hammer – The sound of pipes banging, hammering, or rattling. Hammer suppressor devices can be installed to stop water hammers.

Wax gasket (ring) – A donut-shaped seal installed between the toilet base and the floor to prevent leaks.

Wet venting – A venting system that is connected to a fixture’s drainpipe, tied directly to soil stack.

Y (or wye) – A fitting with three outlet to create branch lines, shaped like a Y.

If there’s a plumbing word or phrase you don’t see in our plumbing glossary, visit or contact the professional plumbers at Fix-It 24/7.

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