IA Plumber key terms

An unobstructed vertical distance between the lowest point of a water-supply outlet and the flood-level rim of the receiving fixture or receptacle. It is the most reliable form of backflow protection because it provides a physical separation.

A piping arrangement in which a drain or waste pipe discharges into a receptacle through an air space rather than a direct connection, preventing sewage from backing up into fixtures or equipment. It protects drainage connections rather than potable water outlets.

The unintended reverse flow of water, liquids, or gases through a piping system, opposite to the intended direction. It can result from backpressure, where downstream pressure exceeds supply pressure, or from backsiphonage caused by negative pressure.

Any actual or potential physical link between a potable water system and a source of contamination or pollution that would allow foreign material to enter the drinking water supply. Cross-connections must be eliminated or protected by an approved backflow preventer.

A testable assembly with two independently acting check valves and a pressure differential relief valve located between them. It protects against both backpressure and backsiphonage and is used on high-hazard connections.

A backflow device with a float check that opens to admit air when supply pressure drops, breaking a siphon. It must be installed at least six inches above the highest downstream outlet and may not be under continuous pressure.

The column of water retained in the dip of a trap that blocks sewer gas from entering a building. It must be deep enough to resist pressure fluctuations yet shallow enough to avoid self-siphoning.

A trap shaped like the letter P that creates a water seal between a fixture and the drainage system while letting waste pass through. It must be self-cleaning, of uniform bore, and installed level.

The section of pipe connecting a trap outlet to the vent or drain into which it discharges. Its length and slope are limited so that the trap seal is not siphoned out.

The pipe that carries waste from a fixture's trap to the point where it joins another drain or stack. It includes the trap arm portion but does not include the trap itself.

A unit of measure expressing the probable rate at which waste discharges from a fixture, used to size drainage piping. One DFU roughly equals a lavatory; water closets carry substantially higher values.

The total length of pipe measured along its centerline, including all horizontal and vertical runs and fittings, but excluding the vertical drop through tee fittings. It is used in sizing and pressure-loss calculations.

The vertical drop of a horizontal drainage pipe over a given horizontal distance, usually stated in inches per foot or as a percentage. Adequate slope keeps solids moving without leaving liquid behind.

A vertical pipe that carries sewage, including solids from water closets, from fixtures down to the building drain. It extends upward to the point where it is vented to outdoor air.

The extension of a soil or waste stack above the highest fixture connection, open to outside air to relieve pressure within the stack. It is simply the upper portion of the stack itself.

A vertical vent pipe installed to provide air circulation to a drainage system, connecting vents from lower floors up to the vent terminal. It serves the venting needs of the stack rather than a single fixture.

The open end of a vent pipe where it terminates outdoors, allowing air to enter and sewer gases to escape. It must be located away from windows, doors, and air intakes to prevent odors and gas entry.

A vent pipe serving a single fixture trap, connecting its trap arm to a vent stack or stack vent. It protects the trap seal of just one fixture.

A one-way mechanical device installed on a vent pipe that admits air when negative pressure develops in the drainage system and seals closed to keep sewer gas inside. It provides venting without a pipe through the roof.

The lowest pipe of a building's drainage system, receiving waste from all soil, waste, and other drains and discharging to the building sewer. It extends to a point outside the building wall, commonly about two feet beyond.

The pipe that carries sewage from the building drain to a public sewer, private disposal system, or other point of disposal. It begins where the building drain ends.

An accessible opening fitted with a removable plug in drainage piping so blockages can be cleared with a rod or auger. Cleanouts are required at the base of stacks and at changes of direction.

A receptacle installed in the drainage line from a commercial kitchen that slows flow so fats, oils, and grease float and are retained before wastewater reaches the sewer. Accumulated grease must be removed periodically.

The pipe carrying water from a public main or other source to the building, ending where the water distribution system begins. It must withstand the highest pressure in the system.

The piping inside a building that carries hot and cold water from the service or water-heating equipment to the fixtures. Sizing must limit pressure loss while keeping velocity and noise reasonable.

The pressure remaining at a fixture outlet or other point in a piping system while water is flowing. It must be high enough to operate fixtures properly, while excessive pressure requires a regulator.

A device containing a trapped air chamber or piston that absorbs the shock wave created when valves close quickly in a pressurized piping system, preventing noise and pipe damage.

A safety device on a water heater that opens to release water or steam when temperature or pressure inside the tank exceeds safe limits, preventing a rupture. It must be fitted with a full-size discharge pipe.

A closed tank installed on a water heating system that absorbs the extra volume created as water is heated and expands, keeping pressure from rising too high in a closed system.

The air supplied to a gas appliance for burning fuel, plus excess air and often dilution air for venting. An adequate supply must be provided to prevent incomplete combustion and carbon monoxide production.

A short vertical drop in a gas line with a capped outlet, installed just before an appliance's controls to catch dirt, scale, and moisture that could clog orifices. Gas flows down into it and then up to the burner.

An approved flexible or semi-rigid length of pipe used to connect a gas appliance to the building gas piping, permitting movement, vibration, or easy removal. It must be listed for the purpose and protected from damage.

A formal authorization issued by the code authority before work begins, allowing specified plumbing work to be done and inspected in stages. Work performed without one may have to be removed and redone.

The official or agency responsible for enforcing and interpreting the plumbing code, such as a building official or plumbing inspector. The AHJ approves plans, conducts inspections, and may require tests.

Accepted by the authority having jurisdiction as meeting code requirements, whether through listing, testing, or the authority's judgment. All installed materials, fixtures, and methods must be approved.

Included in a published list of equipment or materials tested and certified by an approved testing agency for a specific use. Listed equipment is generally accepted as approved by the authority.

A change, addition, or modification to an existing plumbing system, such as relocating a fixture or replacing pipe with a different material. Alterations must comply with code requirements for new work.

A valve that uses line pressure to deliver a measured volume of water to a fixture, usually a water closet or urinal, then closes automatically after the flush. It needs adequate pressure and flow to work properly.