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Plumbing Repair Glossary

Brian Gregory

By Brian Gregory
Updated October 21, 2022

Your home's plumbing system can be intimidating. Lowe's has all the information you need to make repairs and updates on your own, without being overwhelmed.

A man tightening a pipe under a sink.

Techniques for Plumbing

Dry Fit: Connecting pipe without adhesive for the purpose of checking measurements

Roughing In: Positioning and installing supply and drain-waste-vent pipe in walls and floors, while the walls and floors are unfinished; roughing in doesn't include connecting fixtures

Solvent Welding: Joining two things together by using a solvent, which softens the materials, then evaporates after adhering them

Snaking: Clearing blocked drains by pushing and twisting a drain-and-trap auger

Sweating: Connecting copper pipe and fittings with soldered joints

Tapping In: Connecting new pipe to an existing plumbing line to serve a new fixture

Threaded Connections: Connecting pipe together by screwing them in using the spiral ridges on the ends of the pipe

Valve Dressing: Grinding a worn valve seat with a special tool to stop drips in compression faucets

Pipe Fittings

Adapter: a fitting that joins pipe made of different materials or sizes

Bushing: a fitting that joins pipe made of different sizes, threaded inside and out

Cap: a fitting that covers and seals the end of a pipe

Coupling: a fitting that makes a connection between two straight runs of pipe

Ell: an elbow joint with hubs on both ends used to make an angled connection between two straight runs of pipe

Hub: the wide end of a fitting that allows insertion of a pipe for making a joint

P-Trap: a curved section of pipe that prevents sewer odors from escaping into the house; required on all fixtures with a drain

Street Ell: an elbow joint with a hub on one end used to make an angled connection between pipe and a fitting with a hub

Tee: a T-shaped fitting that joins three lengths of pipe — two lengths in line with each other and the third length perpendicular to the first two

Toilet Flange: an anchoring ring that secures the toilet to the floor while also connecting the toilet to the sewer pipe

Union: a three-piece fitting that joins two sections of pipe while allowing them to be disconnected without having to cut the pipe

Wye: a Y-shaped fitting that joins three lengths of pipe in branch fashion

Supply-System Components

Air Chamber: an extra length of pipe installed vertically on a supply line near a fixture to prevent water hammer

Branch Line: a supply line that branches off the main water trunk with either tees or manifolds to extend water to fixtures.

Compression Fitting: a connector — composed of a threaded body, a compression nut and a compression ring — used on copper and plastic pipe, forming a watertight seal when the body and nut are tightened, squeezing the ring around the pipe

Riser: a supply pipe that runs vertically from floor to floor

Service Pipe: the pipe that delivers cold water to the house from a water main or well

Shut-Off Valve: a valve that cuts off water to one or more fixtures, allowing repairs without shutting off the supply system for the entire house

Waste-System Components

Air Admittance Valve: a one-way, mechanical valve installed at the site of a plumbing fixture, allowing proper venting to occur when negative pressure develops in the pipe due to waterflow.

Air Gap: a Y-shaped fitting that connects to the kitchen sink drain to prevent wastewater from backflowing into your dishwasher, eliminating the risk of dirty water contaminating your clean dishes

Cleanout: an opening, closed by a removable plug, that provides access to a drain or sewage pipe for clearing blockages

Drain Trap: a U-shaped passage at a fixture or in a drain line that stays filled with water to keep sewer gases from escaping from the drain into living spaces

Main Drain: the slanting pipe in the basement or crawlspace that carries waste to a sewer or septic tank; also called a building drain

Septic Tank: a buried tank where waste from the drain system is decomposed and purified

Soil Stack: a large, vertical pipe that carries waste from fixture drains to the main drain

Toilet Wax Ring and Floor Seal: a round ring made of wax or heavy-duty rubber (wax-free) to prevent odors and create a water-tight seal between the floor and the toilet

Vent Stack: a large, vertical pipe that projects above the roof, connected to the soil stack, and vents sewer gases from the soil stack, preventing the gases from entering the living space

Plumbing Problems

Galvanic Corrosion: Corrosion caused by natural chemical interaction between different metals

Siphoning: Suction from dropping water pressure that draws water or waste through the lines

Water Hammer: The banging of pipes against hard surfaces when water flow is suddenly cut off at a fixture

Plumbing Safety

Cross Connection: Occurs when there's a chance that drinking water and nonpotable wastewater could mix; most often happens when the pressure in the system changes or is turned off and nonpotable water is drawn into the supply system

Hydrostatic Testing: A test using noncompressible liquid under pressure at a level equal to or greater than the maximum pressure that will be utilized when in use, such as in steam boilers; used to find leaks

Legionella: A bacteria that tends to grow in hot water heaters in which the water isn't hot enough to kill them; leads to Legionnaire's disease, which has caused many deaths; best means of preventing this bacteria from growing in a hot water system is to set the temperature above 122°F

Scalding: This is a major concern with water heaters because the temperature of the water can get high enough that it scalds the skin upon first coming out of the tap; the elderly and children are the most susceptible to this danger; temping valves are used to keep this from happening

Temperature and Pressure Relief Valve: This valve releases water if the temperature or pressure inside the water heater tank becomes too high, preventing the water heater from becoming dangerous and exploding

Additional Plumbing Resources

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