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Plumbing Terms & Definitions

Plumbing is one of the most important aspects of your home. You should be as informed as possible when it comes time to hire a plumber. Along the way you'll discover many new words you've probably never seen or heard before. We have provided our users a list of these important plumbing terms and their definitions.

1/8 Bend Offset
A plumbing fitting used for positioning a pipe around an obstacle.
Access Panel
Covered opening in a wall or ceiling near a fixture that allows access for servicing a plumbing or electric system.
Arconitrile Butadiene Styrene (ABS)
A type of plastic used to make plumbing pipe.
Air Gap
Vertical, unobstructed distance, between the flood level in a plumbing fixture and the lowest water supply inlet, such as the distance between the rim of the tub and the faucet.
Air Trap
A u-shaped pipe filled with water and located beneath plumbing fixtures to form a seal against the passage of gases and odors.
Acetylene tank holding 40 cubic feet of gas, used for plumbing, once used to fuel Boats, thus the name.
Back Vent
Plumbing fixture's separate vent in a building drainage system.
Balancing Ell
Control of water flow through a heat distribution unit using an elbow plumbing fitting.
Ball Joint
The sphere shaped end of this flexible plumbing joint rests in a socket.
Branch Drain
Plumbing fixture drain to the main drain line.
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.
Closet Auger
A plumbing tool used for clearing obstructions from toilet traps to the mouth of the waste pipe.
A type of fitting with two female ends that receive the smaller ends of piping or tubing, making a connection. A mechanical device or part for joining parts together to make a joint. A type of fitting used to join plumbing pipes.
Directional Tee Plumbing
Tee fitting, which directs flow in one direction by use of an internal baffle.
Drum Trap
Plumbing fixture, which is cylindrical in shape, which retains water as a seal, with an outlet at its top and an inlet at its base. Used in plumbing fixtures that are too low to the floor for installation of a P-trap.
Plumbing fitting, shaped like an elbow, which allows water to flow in a curve. Also referred to as an elbow, it is designed to use with pipe, tubing, conduit, or duct and is available in 90 to 45 degrees.
Finish Plumbing
Installation of plumbing fixtures to make the system usable.
First Draw
Water that has been sitting in pipes or plumbing fixtures overnight and is first drawn when taps are opened in the morning. For instance, where lead is present in plumbing, this water would have the highest levels of lead contamination.
Sinks, toilets, tubs. Plumbing fixtures. Electrical devices connected to electrical current.
Fixture Branch
Pipe that carries wastes from non-toilet plumbing fixtures directly to the building drain. It is also called a waste pipe, wet vent, or fixture drain.
Fixture Drain
Pipe that carries wastes from non-toilet plumbing fixtures directly to the building drain. It is also called a waste pipe, wet vent, or fixture branch.
Flow Control Valve
Device designed to reduce water flow to a plumbing fixture. Often used to improve efficiency and reduce operating costs. Also a check valve that prevents flow reversal when heater is turned off.
Horizontal Branch
Lateral drain pipes which run from the plumbing fixtures to the waste stack in a building or into the soil.
Plumbing drainage fitting that enlarges the diameter of a straight-line run by virtue of its larger size on one end and smaller on the other. If it is used for the reverse, to make the diameter of a straight-line run smaller, it is called a reducer.
Plumbing device, used to prevent sewer gas from entering a building, by keeping a water seal in the drain.
Pipe Ell
Plumbing fitting, shaped like an elbow, which allows water to flow in a curve. Also referred to as an ell, it is designed to use with pipe, tubing, conduit, or duct and is available in 90 to 45 degrees.
Tradesman who installs and repairs plumbing systems.
Collective term for the pipes and fixtures, etc. involved with the movement of fluid throughout a building.
Plumbing Bend
Elbow fitting, used in drain and vent lines, to make a bend at an angle to the main line.
Plumbing Drawing Symbols
Symbols used to denote specific fittings, etc. of drawing.
Plumbing Fixture
Mechanism which both receives and discharges wastes and water into a drainage system.
Plumbing Snake
Thin, flexible length of spiral-wound metal, which is inserted into a drain and rotated to clear anything that is clogged in the pipes.
Plumbing Tree
Prefabricated set of drain waste, vent, and supply lines.
Plumbing Y-Branch
Y-shaped fitting, also called a wye, which has one straight side and a branch joining at an angle and is used to join a branch line and a main run.
Pressure Head
Pressure in a plumbing system. The unit of measure which is the vertical force exerted by water at a depth of one foot.
A plumbing fitting with a 180-degree bend.
Rough In Plumbing
Plumbing system installation which prepares for but does not include the installation of fixtures.
A plumbing trap that takes the shape of the letter S and is used where a waste pipe feeds into the floor instead of the wall, which uses a P Trap. Disallowed in many parts of the country, they can create a siphoning situation, pulling water out of the trap.
A system of pipes, containment and treatment facilities for the disposal of plumbing wastes.
Soil Pipe
A pipe that penetrates a roof and is used to vent a building's plumbing.
Tap Water
Water provided by a water company by way of the home's plumbing system.
A plumbing fitting in the shape of the letter "T," used to connect three sections of pipe.
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.
Surface material on some plumbing fixtures derived from or consisting of glass, translucent, and low on porosity.
Waste Stack
A vertical pipe in a plumbing system that carries the discharge from any fixture.

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