NBOPE Journeyperson Plumber key terms

The measured distance along the centerline of a pipe run, including all fittings, offsets, and bends. Plumbers use it to calculate total pipe needed and to convert fitting takeoffs into accurate cut lengths.

The length of pipe that a fitting occupies, subtracted from a measured center-to-center or end-to-end distance so the cut piece fits properly. Values come from manufacturer dimensions or standard tables.

The amount of length a fitting consumes at a joint, commonly measured from the fitting face to the centerline intersection. Subtracting takeoffs from a run gives the true pipe cut length.

The diagonal length of an offset in a piping run, measured along the pipe between the two fittings. It is calculated from the offset and the fitting angle, commonly using the 45-degree multiplier of 1.414.

A pair of matching bends that shifts a pipe run sideways, usually to clear an obstruction or align with a fixture. The offset is the perpendicular distance between the two parallel pipe lines.

The downward pitch of a horizontal drain, expressed as unit of drop per unit of run or as a percentage. Adequate fall carries solids while limiting water velocity and noise in the pipe.

A load rating that expresses the probable discharge rate of a fixture in gallons per minute, used to size drainage piping. Values are assigned by code tables based on fixture type and use.

A vertical drainage pipe that carries waste or soil from fixtures down to the building drain. Soil stacks serve water closets, while waste stacks serve other fixtures; both require venting.

The lowest horizontal portion of the drainage system inside the building, receiving discharge from stacks and branches and conveying it to the building sewer. It ends at the building wall or foundation line.

The pipe that carries sewage from the building drain to the public sewer or private disposal system. It lies outside the building foundation and is typically governed by separate site utility rules.

A device installed on a drainage line that closes automatically to prevent sewage from reversing into the building during a sewer surcharge. It must be accessible for inspection and maintenance.

An accessible fitting with a removable plug or cover that allows a drain line to be rodded or jetted clear of blockages. Codes specify required locations, spacing, and size relative to the pipe served.

A vertical pipe that extends from the drainage system to outdoor air, equalizing pressure in the drains and protecting trap seals. It may serve as a soil or waste stack vent or as a separate vent.

The water held in the dip of a fixture trap that blocks sewer gas from entering the building. Its depth is typically 2 to 4 inches and is protected by proper venting and fixture use.

A one-way valve that admits air into a drain when water flows and seals closed when pressure equalizes, protecting trap seals without a through-roof vent. Codes limit its use and require accessibility.

The pipe section between a fixture trap and the point where it connects to a stack or branch, sized and limited in length by code. Its length affects whether the trap requires additional venting.

A rating of the probable water demand of a fixture, used with demand curves or tables to size water distribution piping. It accounts for fixture flow rate and the likelihood of simultaneous use.

A device that lowers incoming water pressure to a safe, usable level for the building distribution system. Excessive pressure stresses fixtures and fittings, while low pressure causes poor fixture performance.

The increase in water volume as it is heated, which raises pressure in a closed system such as one with a backflow preventer or check valve. An expansion tank or relief device controls the resulting pressure.

A pressure surge caused by the sudden stop of water flow, producing banging and stress on piping. Arrestors, properly sized piping, and gradual valve closure reduce or absorb the shock.

A physical separation between a water supply outlet and the flood level rim of a fixture or vessel. It is the most reliable form of backflow protection and requires no moving parts.

An assembly or device that stops reverse flow of water caused by backsiphonage or backpressure, protecting the potable supply. Common types include reduced-pressure zone, double-check, and pressure vacuum breaker assemblies.

Any actual or potential link between the potable water system and a source of contamination or pollution. Eliminating or protecting cross-connections is the core purpose of backflow prevention programs.

The uppermost edge of a fixture, receptor, or vessel from which water can overflow. It establishes the reference point for air gaps and for locating fixtures that must drain by gravity.

The drain opening at the bottom of a fixture through which waste exits. Its size and the shape of the outlet determine flow capacity and must match the trap and drain sizing.

A safety device that opens to discharge water if tank temperature or pressure exceeds set limits, preventing rupture. It must be piped to a safe discharge point and never plugged or capped.

A sacrificial metal rod inside a storage water heater tank that corrodes preferentially to protect the steel lining. Inspecting and replacing it extends tank life, especially in aggressive water areas.

A short downward leg of piping at a gas appliance connection that collects dirt and condensate before gas enters the controls. It must be installed so debris does not pass into the appliance orifices.

A vertical section of gas piping, capped at the bottom, installed at the lowest point before a gas appliance or regulator. It traps moisture and particulate matter carried in the gas stream.

A manual valve installed in the gas piping near an appliance that lets the gas supply be isolated for service or emergency. It must be accessible and clearly identified.

An official authorization issued by the authority having jurisdiction to perform plumbing work. It establishes a record of the project and triggers required inspections before the work may be covered or used.

The organization, office, or individual responsible for enforcing code requirements and approving materials, installations, and inspections. Local amendments and interpretations come from this authority.

An inspection performed after piping, vents, and fixture supports are installed but before walls, floors, or ceilings are closed. Approval is required before covering work that the inspector must see.

A unit of measure that combines flow rate and probable use to express the load a fixture places on a plumbing system. Separate scales exist for drainage and for water supply sizing.

A vent that also serves as a drain for fixtures on the floor above, carrying both air and waste. Code limits the fixtures and distances allowed on a wet vent to prevent trap seal loss.

The condition of potable water with respect to contaminants, hardness, taste, odor, and corrosiveness. Plumbers address it through material selection, filtration, treatment, and protection from contamination.

A fixture that receives human waste and discharges it through a trap to the drainage system. Its flush volume, trapway, and connection size affect drainage fixture unit loading.

Safety gear such as eye protection, gloves, respirators, and hearing protection worn to reduce injury risk on the job. Proper selection and fit are required when working with chemicals, solvents, and power tools.