IAPMO UPC PI key terms

The organization, office, or individual responsible for enforcing the code, interpreting its provisions, and approving materials, equipment, and installations. Inspectors and plan reviewers act as the AHJ's representatives.

A written authorization issued by the AHJ allowing work described in an application. Work may not begin until the permit is issued, and the permit lapses if work is not started or inspected within the time the code sets.

The AHJ's pre-construction examination of submitted drawings and specifications to verify code compliance before a permit is issued. Reviewers check fixture counts, pipe sizing, venting, and gas load calculations against the code.

An inspection performed after piping is installed but before it is covered, concealed, or permanently connected, allowing the inspector to verify sizing, slope, support, and venting while the work is still visible.

The closing inspection conducted when the work is complete, confirming that fixtures, appurtenances, and connections are installed, tested, and functioning as approved before the system is placed in service.

A pressure test of a drainage or water supply system performed by filling it with water and observing it for a set period. Leaks, drops in pressure, or visible seepage indicate failure.

A test in which a drainage system is sealed and pressurized with air to a specified pressure and monitored for leakage. It is an alternative to water testing where freezing, weight, or site conditions make hydrostatic testing impractical.

The depth of water held in a trap's dip that blocks sewer gas from entering a building. The code sets a required depth, and the seal is lost by evaporation, siphonage, backpressure, or capillary action.

The pipe segment between a fixture trap and the point where it connects to a branch or stack. Its length and fall are limited by the code so the trap seal is not self-siphoned.

A pipe or opening that admits air into a drainage system to protect trap seals from siphonage and backpressure and to allow sewer gases to escape outdoors above the roof.

A vertical vent pipe that extends through the roof and serves one or more drainage stacks, providing relief air to the drainage system. It must terminate at the required height above roof and openings.

A general term for a main vertical pipe in a drainage or venting system. A soil stack carries fixtures with solids; a waste stack carries fixtures without solids; a vent stack carries air.

The lowest piping inside a building that receives the discharge of soil, waste, and other drainage pipes and conveys it to the building sewer. It is typically sized and sloped for gravity flow.

The pipe conveying sewage from the building drain to the public sewer or private disposal system. It begins outside the building foundation wall and is often governed by separate requirements from the building drain.

An accessible fitting with a removable plug or cap that allows a drain or sewer to be rodded or cleared of blockages. The code prescribes where cleanouts are required and how they must be accessible.

A dimensionless measure of the probable drainage load or water supply demand of a plumbing fixture, used to size pipes and vents. One fixture unit approximates the load of a lavatory.

The fixture-unit value assigned to a fixture based on its discharge rate and characteristics, used to size drainage pipes, branches, and stacks in accordance with code tables.

The fixture-unit value reflecting a fixture's probable hot and cold water demand, used to size water distribution piping and the water service. Values differ for cold, hot, and total demand.

The pipe and fittings that convey potable water from the public main or private source to the building, ending at the point where the building's water distribution system begins.

Piping within a building that conveys potable water from the service to fixtures and appliances. Sizing depends on fixture-unit demand, developed length, pressure, and allowable friction loss.

A device installed in a water supply line to lower incoming pressure to a safe, usable level for the building's piping and fixtures. It is required where supply pressure exceeds the code limit.

An assembly or device that prevents reverse flow of contaminated water into the potable supply. Selection depends on the degree of hazard and must match the assembly type approved for that hazard.

Any actual or potential link between the potable water supply and a source of contamination or pollution. Cross-connections must be eliminated or protected by an approved backflow prevention method.

An unobstructed vertical separation between a water supply outlet and the flood-level rim of a receiving vessel. It is the most reliable form of backflow protection because it relies on no moving parts.

A device that admits air into piping to break a vacuum and prevent backsiphonage. Atmospheric and pressure-type versions are applied to specific fixtures and must be installed in the orientation the listing requires.

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 noise and damage.

The increase in water volume as it is heated, which raises pressure in a closed system. A thermal expansion tank or other approved means must control this pressure to protect piping and components.

A device or arrangement that supplies a small amount of water to a floor drain or similar trap to maintain its seal where infrequent use would otherwise allow evaporation to break the seal.

A drain fitting set in a floor to receive surface water and discharges. It requires a trap, must be accessible for cleaning, and often needs a trap primer where it is used infrequently.

The system of pipe, tubing, and fittings that conveys fuel gas from the point of delivery to appliances. Sizing, materials, support, and bonding are governed by code and manufacturer listing.

A dirt pocket or drip leg installed at the appliance connection to capture debris and condensate before it reaches the gas controls. It must be installed in the direction the code and listing specify.

A listed flexible or semirigid connector used to join a gas appliance to the building piping. It must be sized for the appliance input, protected from damage, and not used to make rigid pipe runs.

Air supplied to a fuel-burning appliance for proper combustion and draft. The code specifies opening sizes or mechanical means to provide adequate indoor or outdoor combustion air.

An appliance that heats potable water for domestic use. Installation requirements cover relief valves, discharge piping, seismic strapping, venting, and clearances from combustible construction.

A safety device on a water heater that opens to relieve excess temperature or pressure. Its discharge must terminate in an approved location, typically outside or to a safe drain, without reduction in pipe size.

The minimum unobstructed space required in front of and beside a plumbing fixture so it can be used and cleaned. Clearances vary by fixture type and are checked during plan review and inspection.

A plumbing fixture that receives human waste and discharges it through a trap to the drainage system. Installation requires proper rough-in dimensions, clearance, water supply, and a code-compliant flush volume.

A fixture designed and installed to be usable by people with disabilities, meeting requirements for height, reach, clearance, controls, and insulation of exposed piping, as referenced by accessibility standards.