OBC Plumbing House key terms

A unit of measure that expresses the probable load a plumbing fixture places on the drainage or water supply system, allowing dissimilar fixtures to be added into one comparable design load.

A value assigned to a fixture reflecting its rate of discharge and likely simultaneous use, used to size drain pipes and stacks rather than counting fixtures individually.

A value reflecting the probable demand a fixture places on the potable water distribution system, accounting for flow rate and frequency of use when sizing supply piping.

The depth of water held in a fixture trap that blocks sewer gas from entering a building, measured from the trap weir to the dip of the trap arm connection.

The uppermost point of the dip tube in a trap where water begins to spill over into the drain, establishing the water level that creates the trap seal.

A U-shaped fitting beneath or behind a fixture that retains a water seal while allowing waste to pass, named for its resemblance to the letter P.

A vertical pipe that extends from the drainage system to open air, equalizing pressure so trap seals are not siphoned and sewer gases are safely released outdoors.

The principal vertical drain pipe that carries sewage from water closets and other fixtures down to the building drain, often continuing upward as a vent.

The lowest horizontal portion of the drainage piping inside a building that receives waste from all stacks and conveys it to the building sewer.

The pipe that carries sewage from the building drain to the public sewer, private disposal system, or other point of disposal outside the structure.

The length of a soil or waste stack measured between successive horizontal branch connections, used when determining allowable stack loading and vent sizing.

An accessible fitting with a removable cap that provides entry into a drain line so blockages can be cleared with drain-cleaning tools without cutting pipe.

A one-way mechanical device installed on a vent line that admits air to relieve pressure but closes to prevent sewer gas from escaping into the building.

An unobstructed vertical separation between a water supply outlet and the flood-level rim of a fixture, providing the highest form of backflow protection.

A device or assembly that stops contaminated water from reversing flow into a potable supply, typically installed at service connections, boilers, and irrigation lines.

Any actual or potential physical link between a potable water system and a source of contamination or pollution that could allow backflow to occur.

A device that uses atmospheric pressure to prevent backsiphonage by opening and admitting air when supply pressure drops below atmospheric pressure.

The total measured length of pipe including all straight runs, fittings, and valves converted to equivalent pipe length when calculating friction loss in a supply line.

A loud banging or hydraulic shock in piping caused by the sudden stopping of water flow, controlled with air chambers, arrestors, or properly sized pipes.

A device that lowers incoming water pressure to a safe, usable level for fixtures and appliances, protecting piping and preventing excessive flow at outlets.

A safety device on a storage water heater that opens to release excess pressure or temperature, preventing tank rupture or dangerous overheating.

A tank that absorbs the increased volume of water as it is heated in a closed system, preventing excessive pressure buildup and relieving stress on piping and valves.

The edge of a fixture over which water would overflow onto the floor, used to establish the required height of air gaps and backflow protection.

A plumbing fixture that receives human waste and discharges it into the drainage system through a trap, commonly known as a toilet.

A drain set in the floor of a room or area that collects surface water and discharges it into the drainage system through a trap, often with a removable strainer.

A fixture or appliance that drains its waste into the drainage system through an air gap or air break rather than a direct connection, protecting potable water and preventing backup contamination.

The network of piping, inlets, and leaders that collects rainwater and surface runoff from roofs and paved areas and conveys it to a point of disposal.

A vertical pipe that carries rainwater from a roof drain or gutter down to the storm drainage system, sized by the roof area it serves.

A drain installed at grade level to collect surface water from an open area such as a driveway or courtyard and route it to the storm drainage system.

A pump installed in a pit that removes accumulated groundwater or stormwater from a basement or low area, discharging it to an approved point of disposal.

A one-way valve installed on a drain or sewer line that closes automatically to prevent sewage from backing up into a building during surcharge conditions.

An official authorization issued by the authority having jurisdiction that allows plumbing work to proceed and subjects it to required inspections before approval.

The organization, office, or individual responsible for approving equipment, materials, installations, and enforcing the plumbing code in a given area.

An inspection performed after piping and fixtures are installed but before walls and floors are closed, verifying code compliance of concealed work.

The last inspection conducted after all plumbing work is complete and fixtures are set, confirming the system is functional and approved for use.

The vertical pipe assembly that connects a building's fire sprinkler system to its water supply, often including valves, gauges, and a main drain.

A fixed piping system with hose connections at various levels that provides water for firefighting operations inside a building, supplied by a riser or pump.

A connection made by melting a filler metal into the space between copper tube and fitting, forming a leak-resistant bond without melting the base metal.

A connection for plastic pipe made by applying solvent cement that softens the surfaces and fuses pipe and fitting into a single continuous material.

A fitting that separates dissimilar metals, such as copper and steel, to prevent galvanic corrosion at the connection point in a piping system.

A connection made with gaskets, clamps, or threaded components rather than heat or chemicals, allowing assembly and disassembly of pipe and fittings.