NITC Journey Level Plumber key terms

The unobstructed vertical distance between the lowest opening of a water outlet and the flood-level rim of the fixture it serves. It is the most reliable backflow prevention method because no mechanical part can fail.

The unwanted reversal of water flow in a piping system, caused by backpressure or backsiphonage. It can pull contaminants into the potable supply, so codes require approved prevention devices or air gaps.

A device that admits air into a piping system when internal pressure drops below atmospheric, breaking a siphon. Hose-bibb and pressure-type versions are common on outdoor sillcocks and irrigation connections.

The edge of a fixture over which water would spill onto the floor. It establishes the reference point for air gaps and for setting fixture and rim heights during rough-in.

A work area large enough to enter, with limited entry or exit, and not designed for continuous occupancy. Plumbers entering pits or vaults must test the atmosphere and follow permit and attendant rules.

A safety procedure that isolates hazardous energy and applies locks and tags before work begins. Plumbers use it on pumps, water heaters, and circuits so equipment cannot be energized or pressurized unexpectedly.

A pressure test that fills a piping system or container with water and checks for leaks and holding ability. DWV systems are often tested at a specified head of water before walls and ceilings close.

The standardized size label for pipe, such as 1/2 inch or 4 inch, used for ordering fittings and describing systems. It does not equal the actual outside diameter, which varies by material and schedule.

A number that indicates the wall thickness of a pipe for a given nominal size. Higher schedules mean thicker walls and higher pressure ratings, while the outside diameter stays the same.

The measured distance across the outer surface of a pipe or fitting. It governs which joining method and fittings will work, especially with plastic pipe and mechanical couplings.

A chemical adhesive that softens and fuses plastic pipe and fitting surfaces when they are joined. Proper application requires clean, square-cut ends, primer where required, and a short hold time to prevent push-out.

A solvent applied to plastic pipe and fittings before cement to clean and soften the surfaces. Codes and manufacturers specify when it is required, often by pipe size or material.

A fitting with an insulating barrier that separates dissimilar metals, such as copper and steel, to stop galvanic corrosion. It is commonly installed at water heater connections and where piping material changes.

The deterioration of one metal when two different metals touch in the presence of an electrolyte such as water. It eats away the less noble metal and can cause pinhole leaks, so code requires dielectric separation.

A copper connection made by heating the fitting and filling the gap with melted solder. The joint depends on clean surfaces, correct flux, and enough heat for capillary flow, not on the solder alone.

A paste or liquid that cleans and protects heated metal from oxidation so solder flows properly. It is applied to cleaned pipe ends and fittings before soldering and must be residue-free afterward.

A U-shaped fitting that holds a water seal to block sewer gas from entering a building. It must be self-cleaning, properly vented, and set at the correct depth, and it cannot be double-trapped.

The depth of water held in a trap, measured from the trap weir to the top of the trap dip. It must be within code limits so it is not siphoned out and still blocks sewer gas.

The sloped section of pipe that connects a fixture trap to the drain and vent system. Its length and fall are limited, and it must be vented within the allowed distance from the trap.

A vertical pipe that provides air to the drainage system and lets sewer gas escape above the roof. It protects trap seals by keeping pressure balanced and must extend the required distance above the roof surface.

A one-way valve that admits air into a drain line when negative pressure occurs and seals shut otherwise. It may replace a vent under conditions and only where the code and listing allow.

The downward pitch of horizontal drain pipe, usually expressed in inches per foot. Too little slope causes solids to settle, while too much allows water to outrun waste, so codes set minimum and maximum values.

The combined drain, waste, and vent piping that carries sewage and wastewater out of a building while protecting trap seals. It is sized by fixture units and tested before being concealed.

A numerical value that expresses the load a fixture places on the drainage or water supply system. Scores are added to size pipes and vents, so the fixture count directly determines pipe diameter.

A rating of the probable demand a fixture places on the water distribution system. It accounts for the fact that not all fixtures run at once, so pipe sizing is based on expected peak demand.

A device that lowers incoming water pressure to a safe, usable level for the building. It protects fixtures and appliances and is often set between 50 and 75 psi where supply pressure is excessive.

The banging noise and pressure surge caused when water flow stops suddenly in a pipe. Arrestors, properly sized piping, and secure support reduce the shock that can damage joints and valves.

An appliance that heats and stores or delivers hot water for domestic use. Installation requires a temperature and pressure relief valve, a proper vent or flue, and dielectric connections where metals differ.

A temperature and pressure relief valve that opens to release excess heat or pressure from a water heater. It must be rated for the heater, properly piped, and never capped or plugged.

The stage when supply and drain piping is installed to exact locations before fixtures are set. Correct dimensions, blocking, and heights prevent later rework and are checked at inspection.

The code inspection of piping and framing before concealment or fixture installation. It verifies size, slope, venting, support, and testing, and must pass before walls are closed.

A three-dimensional style drawing showing piping runs on angled axes to convey direction and elevation. Plumbers use it to plan and install systems from a flat plan.

A drawing that shows a building or system as seen from above. It locates fixtures, pipe runs, and dimensions in the horizontal plane and is read together with elevations and isometrics.

A schematic drawing that shows vertical piping, floors, and fixture connections without scale. It clarifies how stacks and branches connect through a building and is used for layout and inspection.

The true length of pipe needed along a run, including offsets and bends, before cutting. It is calculated from drawings and fitting dimensions so the installed pipe matches the plan.

A pair of bends that shifts a pipe run sideways to clear an obstruction or change alignment. Its dimensions are calculated from the fitting angle and the required rise or run.

The diagonal length of pipe between two fittings in an offset. It is found from the offset rise and fitting angle, and the correct value prevents short or long cuts.

A model plumbing code adopted by many jurisdictions to regulate installation, materials, and inspection. Local amendments control, so the plumber must confirm which edition and rules apply in the jurisdiction.

An official authorization to perform plumbing work, issued after plans and fees are submitted. Work must follow the approved scope and pass inspections, and unpermitted work can require removal or rework.

An accessible fitting with a removable plug that allows a drain line to be cleared of blockages. Codes require them at specified intervals and at the base of stacks and changes in direction.

A flexible cable tool used to clear blockages in drain lines. Correct use and head selection depend on the blockage and pipe material, since aggressive tools can damage plastic or older pipe.

The rubber valve in a toilet tank that lifts to release water into the bowl and seals afterward. A worn or warped flapper causes a running toilet and is a common service repair.

The tank component that refills the bowl and tank after a flush and shuts off at the set level. A misadjusted or failing valve causes continuous water noise or overflow into the overflow tube.