Master Plumber key terms

The official or agency that enforces the plumbing code in a given area and approves equipment, materials, and installations. Inspectors representing the AHJ sign off on permits and final approvals.

A written authorization from the local building department allowing plumbing work to begin. It triggers required inspections and creates a public record that the installation was completed to code.

A published, standardized set of plumbing rules, such as the Uniform Plumbing Code or International Plumbing Code, that states and cities adopt, sometimes with local amendments, to regulate installations.

Water that is safe for drinking, cooking, and personal hygiene because it meets health standards for contaminants. Only potable water may be supplied to fixtures used by people.

The pipe that carries potable water from the public main or a private well to the building, ending at the first shutoff valve or meter inside. It operates under street pressure.

A device that lowers incoming water pressure to a safe, steady level for the building's piping and fixtures. It protects against damage from excessive street pressure, often taken as above 80 psi.

A chamber containing a trapped air cushion or piston, installed near a quick-closing valve. It absorbs the pressure surge that would otherwise bang pipes when flow stops suddenly.

A number assigned to each fixture reflecting how much water it demands and how often it is used. Sizing tables add these units to determine the pipe size needed.

A rating of the volume and rate of wastewater a fixture discharges in one minute. Code tables sum DFUs to size the building drain and sewer.

The water held in the dip of a trap that blocks sewer gas from entering the building. It is usually 2 to 4 inches deep and can be lost by evaporation or by siphonage.

A vertical pipe that lets air into the drainage system and releases sewer gas outdoors above the roof. It keeps trap seals from being siphoned out by flowing waste.

A one-way mechanical vent that opens to admit air when a fixture drains and closes to seal out sewer gas. It is allowed only where the code permits and must remain accessible.

The lowest horizontal piping inside a building that receives soil and waste from stacks and conducts it to the building sewer, which begins outside the foundation.

A removable plug or fitting giving access to a drain for clearing blockages with a cable or rod. Codes require them at the base of stacks, at changes in direction, and at set intervals.

A one-way flap installed on a drain line that closes when the sewer backs up, preventing sewage from flooding a basement. It must be installed where accessible for maintenance.

A toilet. It is a fixture that receives human waste and flushes it into the drainage system, requiring a water supply, a trapway, and a code-compliant flush volume.

A valve installed on the supply to a fixture or appliance so water can be turned off for repairs without shutting down the whole building. It must remain accessible.

A safety device on a water heater that opens when temperature or pressure exceeds safe limits, discharging hot water and steam to a drain. It must never be plugged or capped.

A small tank with a compressed air bladder that absorbs the extra volume created when water heats and expands in a closed system. Without it, pressure can exceed relief valve settings.

A sacrificial metal rod inside a tank water heater that corrodes instead of the steel tank lining. Inspecting and replacing it extends the life of the tank.

A return pipe or pump circuit that keeps hot water moving from the heater to distant fixtures, so hot water arrives quickly and water is not wasted while waiting.

The standard designation for pipe diameter, which is close to but not exactly the actual outside or inside diameter. Wall thickness is set separately by schedule or dimension standard.

A number that indicates the wall thickness of steel pipe for a given nominal size. Higher schedules mean thicker walls, greater pressure capacity, and a smaller inside bore.

Joining plastic pipe and fittings by applying solvent that softens the surfaces so they fuse together. The joint requires proper priming, full insertion, and cure time before pressure testing.

A fitting with an insulating plastic or rubber separator, installed where copper and steel piping meet, that prevents galvanic corrosion from eating away the metal at the connection.

A flexible plastic tubing widely used for water supply, joined with crimp, clamp, or press fittings. It resists freezing damage better than rigid pipe and needs protection from sunlight and abrasion.

A short downward leg of pipe with a cap, installed at a gas appliance connection to catch dirt and moisture before they reach the burner controls. It must be installed per the manufacturer and code.

The pipe or duct that carries combustion gases from an appliance to the chimney or vent. It must slope upward, be securely joined, and maintain required clearances from combustible materials.

A test in which capped gas piping is filled with air or nitrogen and monitored with a gauge for a set period, proving there are no leaks before gas is turned on.

Any actual or potential link between the potable water supply and a source of contamination, such as a hose submerged in a bucket. It must be eliminated or protected by a backflow preventer.

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

A testable backflow preventer with two check valves and a relief valve that dumps water if pressure reverses or a check fails. It protects against high-hazard cross-connections.

A device that opens to atmosphere when supply pressure drops, breaking a siphon so contaminated water cannot be drawn back into the potable line. Some types must not be under continuous pressure.

A three-dimensional style of plumbing drawing showing pipe runs on angled axes, so lengths, fittings, and elevations can be read from one view. Plumbers use it to lay out DWV and supply systems.

The process of counting and measuring pipe, fittings, fixtures, and equipment from the plans and specifications to build a material list and cost estimate for a job.

A leak test in which water piping or a drainage system is filled with water and held at a specified pressure for a set time, with no pressure drop allowed.

A test of the drainage system in which smoke is forced into the piping and any escaping smoke reveals broken joints or open connections that would leak sewer gas.

An inspection performed after framing and piping installation but before walls are closed, letting the inspector verify pipe sizing, slope, support, and venting.