Journeyman Plumber key terms

The depth of water held in the bend of a plumbing trap, typically 2 to 4 inches, that blocks sewer gases from entering the building. Evaporation, siphonage, or backpressure can destroy the seal and defeat the trap.

The section of pipe between a fixture trap's weir and the point where it ties into a vented drain. Its length and fall are limited by code so the trap seal is not siphoned out.

A vertical pipe that supplies air to the drainage system and carries sewer gases to outdoor air. It typically serves fixtures on more than one floor and extends through the roof.

The extension of a soil or waste stack above the highest fixture connection that runs to open air. It vents the stack itself and is sometimes called a vent extension.

A one-way mechanical valve that admits air into a drain to protect trap seals but does not release sewer gas. Code limits where it may be used, and it usually needs accessible installation.

A number expressing the probable drainage load of a fixture relative to a standard fixture. Fixture units are used to size building drains, stacks, and vents.

The lowest pipe of a building's drainage system, receiving soil and waste from stacks and branches and carrying it to the building sewer. It ends at or near the building wall.

The pipe that carries sewage from the end of the building drain to the public sewer or a private disposal system. It begins outside the building foundation.

A vertical drainage pipe that carries the discharge of water closets, with or without other fixtures, down to the building drain.

A drain pipe that connects fixture drains to a stack or building drain and runs at a slope, no more than 45 degrees from horizontal.

An accessible fitting with a removable plug that allows a drain line to be rodded or snaked. Code requires them at stack bases, on long horizontal runs, and at certain changes of direction.

A one-way check device installed in a drain to prevent sewage from backing up into the building when the public sewer surcharges.

The total length of pipe measured along its centerline, following every fitting and change of direction, rather than the straight-line distance. It is used to size vents and check trap arm limits.

The construction stage when pipe, fittings, and supports are installed before fixtures are set and walls are closed. Rough-in work must be inspected before it is concealed.

A fixture with a strainer and a trapped body set into the floor to receive surface water and spills. It is usually protected by a trap primer or a deep-seal trap.

A flush valve that uses line pressure to deliver a measured flush to a water closet or urinal. It requires adequate pipe size and pressure at the fixture to work properly.

The unobstructed vertical distance between a water supply outlet and the flood-level rim of the fixture or receptacle it serves. It is the most reliable form of backflow protection.

A device or assembly that stops contaminated water from reversing into the potable supply because of backpressure or backsiphonage.

Any actual or potential link between the potable water system and a source of contamination. It must be eliminated or protected against with an approved device or air gap.

A chamber containing a trapped air cushion or a moving piston that absorbs the pressure surge created when a valve closes quickly, reducing noise and pipe damage.

A device that lowers incoming water pressure to a safe, usable level, protecting fixtures, appliances, and piping from excessive pressure.

The increase in water volume as it is heated. In a closed system this raises pressure and must be relieved by a device such as an expansion tank or a thermal expansion valve.

A safety valve on a water heater that opens when internal temperature or pressure exceeds its rating, discharging hot water to a safe approved location.

A sacrificial metal rod inside a tank-type water heater that corrodes in place of the steel tank, extending the tank's service life.

A piping arrangement that keeps hot water circulating from the heater toward fixtures so hot water arrives quickly, reducing wait time and wasted water.

A fitting on a gas appliance that admits dilution air and stabilizes the draft into the vent, helping prevent flue gases from spilling into the room.

A short downward leg of pipe installed near a gas appliance's inlet that collects dirt, scale, and moisture before they can reach the appliance controls.

A flexible gas piping material sold in coils and joined with special fittings. It must be installed per its listing and bonded to the electrical grounding system.

A header or fitting that splits a single gas supply line into multiple branch lines, each serving an individual appliance or outlet.

A safety procedure that isolates energy sources and applies locks and tags so equipment cannot be energized or started while work is being performed on it.

An area with limited entry and exit that is not designed for continuous occupancy and may contain hazardous air or engulfment hazards. Entry requires testing, permits, and procedures.

Temporary support for an excavation, such as sloping, shielding, or bracing, used to protect workers from cave-ins and falling material.

A pictorial drawing that shows piping in three dimensions along angled axes, used to plan, coordinate, and communicate a system layout.

A pair of fittings joined by a pipe that shifts a run sideways or vertically, used to pass around obstructions or line up with a fixture or stack.

The slope of a drain pipe, expressed as a percentage or as inches of fall per foot of run. It must be enough to carry solids without leaving liquids behind.

The official or agency that enforces the plumbing code in a local area, interprets its requirements, issues permits, and inspects completed work.

Written authorization from the authority having jurisdiction to install or alter plumbing work. It must be obtained before work starts and is closed out after inspection.

Water that is safe for drinking and free of harmful contamination, as supplied to fixtures and appliances throughout the plumbing system.