NCCER Plumbing key terms

The total measured distance a pipe runs along its centerline, including all horizontal and vertical segments and changes of direction, measured before fittings are installed. Used to estimate material quantities and to size pipe for pressure loss.

A method of expressing the pressure loss caused by fittings and valves as an added length of straight pipe of the same size. Added to developed length so friction loss through the whole run can be calculated.

The pressure lost as water moves through pipe, caused by the pipe wall and by turbulence at fittings. It increases with flow rate, pipe length, and roughness, and decreases with larger pipe diameter.

The difference in pressure between two points in a piping system, usually caused by friction, elevation change, or a device in the line. Designers limit it so fixtures still receive adequate pressure.

The pressure created by the weight of a column of water at a given height, equal to about 0.434 psi per foot of elevation. Used to account for height differences between a supply source and fixtures.

The pressure remaining at a fixture or outlet while water is flowing. It must stay above the minimum required by code for the fixture to operate correctly and is checked during flow testing.

The volume of water passing a point in a piping system per unit of time, commonly expressed in gallons per minute. Used to size pipe, select pumps, and match supply to fixture demand.

The speed at which water travels through a pipe, usually stated in feet per second. Excessive velocity causes noise, erosion, and water hammer; codes and good practice set upper limits for supply and drainage piping.

A unit of measure that assigns a relative load value to a plumbing fixture based on its probable flow demand. Fixture units are added together to size water supply and drainage systems for a building.

A value assigned to a fixture representing its probable discharge rate into a drainage system. Values are totaled to determine drain pipe size, trap size, and vent requirements for a building drain.

A loud banging or knocking in piping caused by a sudden stop in water flow, such as a quick-closing valve, producing a pressure surge. Controlled with air chambers, arrestors, or slower-closing valves.

A vertical capped pipe or manufactured device connected near a fixture that traps air to absorb pressure surges when flow stops. It reduces water hammer and protects pipe and fittings from shock.

The slope of a drain pipe, expressed as fall per unit of length, such as one-quarter inch per foot. Proper grade lets waste flow by gravity while keeping liquid moving fast enough to carry solids.

The total vertical drop of a drain line over its run, calculated by multiplying the grade by the length. It must be checked so the pipe fits within available space and still drains properly.

The section of drain pipe between a fixture trap and the point where it connects to a branch or stack. Its length and slope are limited by code so the trap seal is not siphoned out.

The depth of water held in a fixture trap that blocks sewer gas from entering the building. Common seals are two to four inches deep and must be protected by proper venting.

The pulling of water out of a fixture trap by pressure differences in the drainage or vent system, which breaks the seal and allows sewer gas into the building. Prevented by correct venting and trap arm length.

A vertical pipe that provides air to a drainage system and allows sewer gases to escape above the roof. It protects trap seals by equalizing pressure in the drain piping.

The extension of a soil or waste stack above the highest fixture connection, continuing through the roof to open air. It vents the stack and helps maintain atmospheric pressure in the drainage system.

The main vertical drain pipe that carries sewage containing fecal matter from water closets and other fixtures down to the building drain. It must be sized and vented according to the fixtures it serves.

A vertical drain pipe that carries liquid waste from fixtures other than water closets, such as sinks and lavatories. It connects to the building drain and is vented to protect trap seals.

The lowest horizontal portion of a drainage system that receives waste from the stacks and carries it to the building sewer. It is usually located just inside or under the building foundation.

The pipe that carries sewage from the building drain to the public sewer or private disposal system. It begins outside the building foundation and is typically owned and maintained by the property owner.

An accessible fitting with a removable cap installed on drainage piping so blockages can be cleared with a snake or rod. Codes require cleanouts at specified locations, such as the base of stacks and changes in direction.

The unwanted reversal of water flow in a piping system, which can contaminate the potable supply. Prevented with air gaps, vacuum breakers, and backflow prevention assemblies selected for the hazard level.

Any actual or potential link between a potable water system and a source of contamination or pollution. It must be eliminated or protected by an approved backflow prevention device.

The unobstructed vertical distance between a water supply outlet and the flood level rim of the fixture it serves. It is the most reliable form of backflow protection because no mechanical parts are involved.

A device that opens to admit air and break a vacuum in piping, preventing back-siphonage of contaminated water into the supply. Common types include atmospheric and pressure vacuum breakers.

The pipe and fittings that carry potable water from the water main or private source to the building. It includes the meter, valves, and the connection to the building's water distribution system.

A primary pipe in a public or private water distribution network that supplies individual water services. Its size and pressure determine the flow available to connected buildings.

Water that is safe for human consumption and meets health-based quality standards. Plumbing codes require potable water for drinking, cooking, bathing, and other domestic uses.

The phase of plumbing work in which pipes, fittings, and supports are installed before walls, floors, and fixtures are finished. Inspections typically occur after rough-in and before covering the work.

The finished, visible plumbing components installed after rough-in, such as faucets, spouts, escutcheons, and fixture trim plates. Trim work completes the system and is installed during final finishing.

A projecting rim or collar on a pipe or fitting used to make a connection or to support a fixture. In plumbing, closet flanges secure a water closet to the drain and help seal the connection.

A ring of pliable wax placed between a water closet outlet and the closet flange to form a watertight seal. It compresses when the fixture is set and prevents leakage at the floor connection.

A toilet fixture that receives human waste and discharges it into the drainage system through a trap. It is set on a closet flange and connected with a water supply stop and flush valve or tank.

A U-shaped fitting that holds a water seal to keep sewer gas out of the building while allowing waste to pass. It is required at most fixtures and must be vented to protect the seal.

A manufactured device installed in a water supply line to absorb pressure surges and reduce water hammer. It is an alternative to a simple air chamber and is often placed near quick-closing valves.

A device that measures and records the volume of water passing through a service line. It is typically installed at the property line or building entry and may include a backflow prevention component.