DC Plumber key terms

The locally adopted plumbing regulation for the District of Columbia, based on the model plumbing code with District amendments, governing design, installation, alteration, and inspection of plumbing systems within the jurisdiction.

The authority having jurisdiction who enforces the plumbing code, reviews plans, issues permits, conducts inspections, and approves or rejects installed work. In DC this is the authorized building official or designated representative.

The required authorization to perform plumbing work and the staged checks by the code official at defined points, such as rough-in, gas piping pressure test, and final, before a system may be concealed or placed in service.

The stage of installation when piping, fittings, and supports are in place but fixtures and finishes are not, allowing inspection before walls, floors, or ceilings are closed up.

An approved joining technique listed for the specific pipe material and application, such as solvent cementing for PVC, soldering or press for copper, or threaded joints for steel, required for code compliance.

The drainage, waste, and vent piping network that carries sewage and gray water away from fixtures while admitting air to protect trap seals and vent sewer gases outdoors.

The water retained in a fixture trap's dip that blocks sewer gas from entering the building. Its depth is code-specified, commonly between two and four inches, and must be maintained.

A U-shaped fitting installed at each fixture drain that holds the trap seal and prevents backflow of air and gas. Traps must be self-cleaning and protected against siphonage.

A vertical pipe that extends from the drainage system to open air, providing relief for air pressure in the drain and preventing trap seal loss from siphonage or back pressure.

A one-way mechanical vent device that opens to admit air into the drainage system and closes to prevent sewer gas escape, permitted only where the code allows in place of conventional venting.

The downward pitch of horizontal drainage pipe, expressed as a ratio, that lets wastewater flow by gravity. Code sets minimum slopes based on pipe diameter to keep solids moving.

A unit value assigned to each fixture type reflecting its probable drainage load, used to size drain and sewer piping and to determine required venting.

An accessible fitting with a removable plug or cover installed at the base of stacks, ends of horizontal runs, and changes in direction so blockages can be rodded out.

A one-way check device installed on a drainage line to prevent sewage from the public sewer from reversing into the building during surcharge or flooding conditions.

The piping and fittings that deliver potable water at adequate pressure and volume from the service main to fixtures, including distribution mains, branches, and control valves.

The pipe carrying potable water from the public main or private source to the building, ending at the first shutoff valve, meter, or connection inside the structure.

A device containing a trapped air chamber or piston that absorbs the pressure surge created when a valve closes quickly, protecting piping and fixtures from shock and noise.

A regulator installed where supply pressure exceeds code limits, reducing it to a safe level for fixtures and piping and protecting the system from excess stress.

The increase in water volume as it is heated in a closed system, which raises pressure and requires a relief valve, expansion tank, or other approved means to prevent damage.

The unwanted reversal of water flow in a supply system, caused by backsiphonage or backpressure, that can draw contaminants into potable water and create a health hazard.

An approved assembly or device, such as a reduced-pressure zone assembly or double check valve, installed to stop reverse flow and protect the potable water supply from contamination.

The unobstructed vertical distance between a water supply outlet and the flood level rim of the receiving fixture, providing the highest level of protection against backsiphonage.

Any actual or potential link between a potable water system and a source of contamination or pollution, which must be eliminated or protected by an approved backflow assembly.

A device that admits air into a piping system when pressure drops, breaking a vacuum that could siphon contaminants backward. Atmospheric and pressure types serve different applications.

An appliance that heats and stores potable water for domestic use, requiring a temperature and pressure relief valve, a drain pan where specified, and proper venting of combustion products.

The temperature and pressure relief valve on a water heater that opens automatically if temperature or pressure exceeds safe limits, preventing tank rupture or explosion.

A toilet fixture that receives human waste and discharges it through a trap to the drainage system, with code-specified flush volume and mounting requirements.

A device or appurtenance attached to a fixture or its supply, such as a faucet, flush valve, or shower valve, that controls water flow and must carry an approved listing.

The piping system that conveys natural gas or propane from the point of delivery to gas-fired appliances, installed with approved materials, joints, and testing before being placed in service.

A required test in which the gas piping is pressurized with air or inert gas and monitored for a specified period to prove the system is leak-free before gas is introduced.

A dirt pocket installed at the appliance connection to catch debris and condensate before it reaches the gas controls, protecting valves and orifices from fouling.

The air supplied to a gas appliance for safe burning, provided by openings or ducts sized to the appliance input so incomplete combustion and carbon monoxide are avoided.

The approved arrangement of vent pipe or chimney that carries combustion products from a gas appliance safely outdoors, with correct sizing, slope, and termination clearances.

The joining method for plastic pipe in which cement softens the pipe and fitting surfaces so they fuse, requiring proper cleaning, primer where specified, and cure time before pressure testing.

A fitting that separates dissimilar metals, such as copper and steel, to interrupt galvanic corrosion where the two materials connect in a piping system.

A safety procedure that isolates energy sources, such as electrical or gas, and applies locks and tags so equipment cannot be energized or released while work is in progress.

A space with limited entry and exit that is not designed for continuous occupancy, such as a pit or vault, requiring atmospheric testing and attendant procedures before entry.

The gear worn to reduce injury risk on the job, including safety glasses, gloves, hearing protection, and respiratory protection selected for the specific task hazards.