AL Plumber key terms

The official, board, or agency that enforces a code's requirements, approves materials and methods, and interprets the rules. Inspectors acting for that office carry the same authority when making field decisions.

Written authorization from the code authority to install, alter, or repair plumbing work. Work generally may not begin until the permit is issued, and inspections are required before the work is covered.

The stage of construction when pipes, fittings, and supports are installed inside walls, floors, and ceilings but before fixtures and trim are set. Rough-in inspections must pass before covering the work.

A pictorial drawing that shows piping in three dimensions on a flat sheet, using vertical, horizontal, and 45-degree diagonal lines. Plumbers use it to plan offsets and visualize how a system goes together.

A single-line schematic showing the vertical relationship of stacks, floors, fixtures, and vents in a building. It is not drawn to scale but shows sizes, connections, and the path of flow.

The ratio between a distance on a drawing and the real distance it represents, such as one-quarter inch equals one foot. Reading the scale correctly is required to order pipe lengths and set fixtures accurately.

A relative measure of the load a plumbing fixture places on the drainage or water supply system. Values are assigned by code based on fixture type and give designers a common basis for sizing pipe.

A unit expressing the probable rate at which waste discharges from a fixture, used to size drainage piping. One DFU corresponds roughly to the flow from a lavatory.

A unit expressing the probable demand a fixture places on the water distribution system, accounting for intermittent use. Total units are converted to probable flow in gallons per minute for pipe sizing.

The lowest part of a drainage system that receives waste from stacks and branches inside the building and carries it to the building sewer. It ends at the building wall or 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 laid with continuous slope.

A vertical pipe that carries the discharge of water closets and may also receive other fixtures. It extends at least one story and connects at its base to the building drain.

An access fitting with a removable plug that allows a drain or sewer to be rodded or inspected. Cleanouts are required at specified intervals, at changes in direction, and at the base of stacks.

The downward pitch of a horizontal drain, usually stated in inches of drop per foot of run. Proper slope allows solids to move while keeping liquid velocity high enough to scour the pipe.

The depth of water held in a trap's dip that blocks sewer gas from entering the building. Codes require a seal of a specified depth, commonly two to four inches.

The pipe section between a fixture's trap outlet and its connection to a vented drain or stack. Its length and slope are limited so the trap does not self-siphon.

A tank or fitting installed in a drain line that slows flow and separates fats, oils, and grease so they do not clog the sewer. It requires regular cleaning and must be sized for the discharge.

The unobstructed vertical distance between a water supply outlet and the flood level rim of the receiving fixture. It is the most reliable form of backflow protection because no mechanical part can fail.

Any actual or potential link between the potable water system and a source of contamination or pollution. Cross-connections must be eliminated or protected by an approved backflow prevention assembly.

The unwanted reversal of flow of water or other substances into the potable distribution system. It is caused by backpressure, where downstream pressure exceeds supply pressure, or by backsiphonage.

An assembly with two independently acting check valves and a relief valve between them that discharges if either check fails. It protects against both backpressure and backsiphonage and requires annual testing.

A device that admits air into piping when internal pressure drops below atmospheric, breaking a siphon. Atmospheric and pressure types are used on hose outlets and flush valves to protect the water supply.

A vertical vent pipe that provides air to a drainage stack or serves as the upper extension of a soil or waste stack. It protects trap seals by keeping pressures in the system near atmospheric.

The extension of a soil or waste stack above the highest fixture connection that opens to outdoor air. It vents the stack itself and may also serve as a vent for fixtures below.

A single vent that serves two fixture drains connected at the same level on opposite sides of a vertical drain. It keeps both traps sealed when the fixtures discharge at the same time.

A one-way valve that opens to admit air into a drain and closes to prevent sewer gas from escaping. Its use, location, and quantity are limited by code and manufacturer instructions.

The pipe that carries potable water from the water main or private source to the building. It terminates at the point where the building's distribution piping begins.

The pressure remaining at a fixture or outlet while water is flowing. Codes set a minimum to ensure fixtures work properly, and the value is used to size supply piping.

A device with a trapped air charge or piston that absorbs the pressure surge created when a valve closes quickly. It protects piping and fittings from noise and damage caused by the shock.

The increase in water volume as it is heated, which raises pressure in a closed system. It must be handled with an expansion tank or relief device to avoid damage or unsafe conditions.

A safety valve on a water heater that opens when either temperature or pressure exceeds its setting, releasing hot water. It must be piped to a safe discharge point and never capped or blocked.

A closed vessel with a compressed air charge connected to a water heater or system that absorbs the volume of thermally expanded water. It prevents excess pressure and protects fixtures and valves.

A capped vertical leg of piping installed at the bottom of a gas line near an appliance to collect dirt, scale, and condensation before they reach the burner controls.

Air supplied to a gas appliance for burning fuel and for dilution of flue gases. It must be provided through permanent openings or ducts sized by code to ensure complete combustion.

A listed corrugated metal hose assembly used to connect a gas appliance to the rigid piping. It must be installed without kinks or sharp bends and cannot pass through walls or floors.

A device such as a faucet, flush valve, or drain assembly attached to a fixture that controls or directs the flow of water. It must be listed and installed to allow cleaning and repair.

A fixture fitting that meters a measured volume of water into a water closet bowl through a siphon-breaking device. It must be adjusted to deliver the fixture's rated flush and be protected against backflow.