HI Plumber key terms

The unobstructed vertical distance between the lowest opening of 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 tested assembly such as a reduced-pressure zone valve or double check valve that stops contaminated water from reversing into the potable supply. Local rules dictate which device fits which hazard level.

A work area with limited entry and exit that is not designed for continuous occupancy, such as a vault or deep pit. Entry requires atmospheric testing, a permit, an attendant, and rescue provisions.

A safety procedure that isolates energy sources before service or repair. Each worker applies a personal lock and tag to the disconnect so equipment cannot be re-energized unexpectedly.

Gear worn to reduce injury risk, including safety glasses, gloves, respirators, hearing protection, and steel-toe boots. Selection follows a hazard assessment of the specific task and site.

Any actual or potential link between the potable water system and a source of contamination or pollution. Eliminating or protecting cross-connections is central to every plumbing code.

Water safe for human consumption that meets health-based quality standards. Plumbing codes require potable water for drinking, cooking, bathing, and handwashing fixtures.

The pipe carrying potable water from the public main or private source to the building. It typically includes a meter, a main shutoff valve, and sometimes a pressure-reducing valve.

A device that measures the volume of water delivered to a building for billing and leak detection. Meters are installed on the service line, often in a pit or meter box.

A regulator that lowers incoming street pressure to a safe level for the building's piping and fixtures. It protects against leaks and water hammer caused by excessive pressure.

A device containing a trapped air chamber or piston that absorbs the shock wave when a valve closes quickly. It prevents banging noise and protects joints from pressure spikes.

A capped vertical section of pipe near a fixture that traps air to cushion pressure surges. It is a simple, older alternative to a manufactured water hammer arrestor.

A dimensionless measure of the probable load a plumbing fixture places on the drainage or water supply system. Values are assigned by code and used to size pipe.

A rating of the rate at which a fixture discharges waste into the drainage system. Total drainage fixture units determine the required drain and building sewer size.

A rating of the probable demand a fixture places on the supply system, accounting for flow rate and frequency of use. Totals are converted to peak demand for pipe sizing.

The total equivalent pipe length of a run, including straight pipe plus allowances for fittings and valves. Friction loss calculations use developed length rather than measured distance.

Pressure lost as water moves through pipe, fittings, and valves due to resistance. It increases with flow rate, pipe roughness, and length, and must be accounted for in sizing.

The pressure exerted by water at rest, determined by elevation and the weight of the column of water. It is measured without flow and expressed in psi or kPa.

The pressure remaining at a point in the system while water is flowing. It reflects the original static pressure minus friction and elevation losses along the path.

The lowest horizontal pipe that receives waste from inside the building and conveys it to the building sewer. It extends to a point outside the foundation wall.

The pipe carrying sewage from the building drain to the public sewer or private disposal system. It begins outside the foundation and is often subject to separate code requirements.

A vertical pipe that carries toilet and other soil waste from fixtures down to the building drain. It must be vented and properly supported to prevent trap siphonage.

A vertical vent pipe that provides air to the drainage system and relieves pressure in the stacks. It extends above the roof to discharge gases safely outdoors.

The open end of a vent pipe that extends above the roof. Codes set minimum height above the roof and required distances from windows, doors, and air intakes.

The sloped pipe section between a fixture trap and the vent or stack connection. Its length and slope are limited so the trap seal is not siphoned out.

The depth of water held in a fixture trap that blocks sewer gas from entering the building. Codes require a specific minimum depth and maximum loss from evaporation or siphonage.

The loss of a trap seal caused by pressure differences in the drainage system pulling water out of the trap. Proper venting and trap arm limits prevent it.

An accessible fitting with a removable plug that allows a drain line to be rodded or inspected. Codes require cleanouts at specified intervals, changes of direction, and the building sewer.

The downward pitch of a horizontal drain pipe, expressed as a fraction of an inch per foot or a percentage. Adequate slope keeps solids moving while preventing water from outrunning waste.

The plumbing code term for a toilet. It must be installed with a trap, a water supply connection, and clearances that meet code and accessibility requirements.

The top edge of a fixture over which water would spill if the drain were blocked. It sets the reference point for air gaps and backflow protection.

A device that admits air into a pipe when pressure drops, breaking a siphon that could draw contaminated water backward. Common types include hose-bibb and flushometer models.

A fitting that separates dissimilar metals, such as copper and galvanized steel, to prevent galvanic corrosion at the joint. It is common where piping materials change.

Electrochemical deterioration that occurs when two different metals contact each other in the presence of an electrolyte such as water. It can quickly corrode the less noble metal.

An on-site wastewater treatment arrangement with a tank and a drain field. Solids settle and are digested, while liquid effluent seeps into the soil for treatment.

Official authorization from the local authority to perform plumbing work. It triggers required inspections and ensures work complies with the adopted code edition.

A required review by a code official at defined stages of work, such as rough-in and final. Passing each inspection is normally a condition of approval and occupancy.

The stage when pipes are installed and tested before walls are closed and fixtures are set. It is typically inspected to confirm sizing, slope, venting, and support.

The specific edition of a model plumbing code legally in force in a jurisdiction, often with local amendments. Contractors must follow the adopted edition, not the newest publication.

A written modification to the contract scope, price, or schedule signed by both parties. It documents extra work or substitutions so payment and responsibility are clear.

A priced projection of labor, materials, equipment, and overhead for proposed plumbing work. Accurate takeoffs and current pricing improve bid reliability and protect margin.

The process of counting and measuring materials from drawings and specifications to build a cost estimate. It includes pipe lengths, fittings, fixtures, and specialty items.

A written list of incomplete or defective items identified near the end of a project. Completing and verifying punch items is usually required before final payment.