Plumbing terms, defined
Plain definitions of the plumbing words that come up on estimates, inspections and supplier calls, written for plumbers. Each term says where it matters on the job and links the Koira calculator, cost guide or template that goes with it.
A
PlumbingAir admittance valveAn air admittance valve is a one way valve that lets air into a drain line when water flows, then closes to keep sewer gas in.PlumbingAir gapAn air gap is an open vertical space between a water outlet, or a waste pipe, and the flood rim of the fixture or drain it empties into.PlumbingAnode rodAn anode rod is a metal rod inside a tank water heater that corrodes on purpose, protecting the steel tank from rust.
B
PlumbingBackflow preventerA backflow preventer is a valve assembly that stops water from flowing backward from a hose, irrigation system or boiler into the drinking water supply.Shared with HVACBoilerA boiler heats water, or makes steam, and circulates it through pipes to radiators, baseboard or floor tubing to heat a building.PlumbingBuilding drainThe building drain is the lowest drain pipe inside the house, collecting everything from the other drains and carrying it out to the building sewer.Shared with General ContractorBuilding permitA building permit is the local government's approval to do regulated construction work, with inspections at set stages.PlumbingBuilding sewerThe building sewer is the pipe that runs from the end of the building drain outside the house to the public sewer or the septic tank.
C
PlumbingCleanoutA cleanout is a capped opening in a drain line that gives access to clear a clog or run a camera.Shared with HVACCondensate lineThe condensate line carries water that drips off the cooling coil, or out of a high efficiency furnace, to a drain or outside.PlumbingCPVC pipeCPVC is a rigid plastic pipe rated for hot and cold water supply, joined with solvent cement.PlumbingCross connectionA cross connection is any link between the drinking water system and another piping system or source that could let something flow into the drinking water.Shared with General ContractorCut sheetA cut sheet is the maker's one or two page product sheet with dimensions, ratings and install requirements for a fixture, appliance or material.
D
Shared with Appliance RepairDiagnostic feeA diagnostic fee is the set charge for coming out and finding what is wrong, before any repair is approved.PlumbingDielectric unionA dielectric union joins two different metals, such as copper and steel, with an insulating barrier so they do not corrode each other.PlumbingDiverter valveA diverter valve sends water to one outlet or another, such as from a tub spout to a shower head, or between body sprays.PlumbingDrain slopeDrain slope is how much a horizontal drain pipe drops along its length, so waste flows by gravity without leaving solids behind.
F
Shared with Appliance RepairFirst-time fix rateFirst-time fix rate is the share of service calls finished on the first visit, without a return trip for parts or a second tech.PlumbingFixture unitA fixture unit is a number the code assigns to each plumbing fixture to estimate its load.Shared with ConcreteFrost lineThe frost line is how deep the ground freezes in a given area.
G
PlumbingGalvanized pipeGalvanized pipe is zinc coated steel water pipe found in older homes.PlumbingGas lineA gas line is the piping that carries natural gas or propane from the meter or tank to appliances, in black iron, CSST or other approved material.PlumbingGPMGPM means gallons per minute, the flow rate of water through a pipe, fixture, pump or nozzle.
H
PlumbingHose bibbA hose bibb is an outdoor faucet with a hose thread.PlumbingHydro jettingHydro jetting is cleaning a drain or sewer line with a high pressure water hose and nozzle that scours grease, scale and roots off the pipe walls.Shared with HVACHydronic heatingHydronic heating moves heat with hot water pumped from a boiler through baseboard, radiators or tubing in the floor.
P
PlumbingP-trapA P-trap is the curved section of drain pipe under a fixture that holds a little water, the trap seal, which blocks sewer gas from coming up the drain.PlumbingPEX pipePEX is flexible cross-linked polyethylene tubing for water supply lines, joined with crimp, clamp or expansion fittings.Shared with RoofingPipe bootA pipe boot is the flashing that seals a plumbing vent pipe where it comes through the roof, with a rubber collar that hugs the pipe.Shared with RemodelingPipe chaseA chase is an enclosed vertical or horizontal space framed to hide pipes, ducts or wires as they pass through a building.PlumbingPipe dopePipe dope is paste thread sealant brushed on tapered pipe threads to seal the joint.PlumbingPipe nippleA pipe nipple is a short length of pipe threaded on both ends, used to connect fittings, valves and equipment.PlumbingPipe sizingPipe sizing is choosing supply pipe diameters so every fixture gets enough flow and pressure at the same time, based on fixture units, pipe length and the starting pressure.PlumbingPolybutylene pipePolybutylene is a gray or blue plastic supply pipe used in many homes decades ago that is prone to failing at fittings and from within.PlumbingPressure reducing valveA pressure reducing valve is an adjustable valve on the main water line that lowers high street pressure to a safe level for the house.PlumbingPVC and ABS drain pipePVC, which is white, and ABS, which is black, are the rigid plastic pipes used for drain, waste and vent lines.
S
PlumbingSewage ejector pumpA sewage ejector pump lifts waste from fixtures below the sewer line, such as a basement bathroom, up to the gravity drain.PlumbingSewer camera inspectionA sewer camera inspection runs a waterproof camera on a cable through the sewer line to see cracks, roots, bellies and blockages.Shared with TileShower panThe shower pan is the sloped, waterproofed floor of a shower that sends water to the drain, built from mortar and a liner, a foam system or a preformed base.PlumbingShutoff valveA shutoff valve stops water to the whole house, a branch or a single fixture.PlumbingSlab leakA slab leak is a leak in a water line running under or inside a concrete slab foundation.PlumbingStub-outA stub-out is the end of a supply or drain pipe left sticking out of a wall or floor at rough-in, capped, ready for the fixture to connect at finish.PlumbingSump pumpA sump pump sits in a pit at the low point of a basement or crawl space and pumps out groundwater that collects there.
T
PlumbingT and P valveThe T and P valve on a water heater opens to release water if the tank gets too hot or the pressure too high, so the tank cannot burst.PlumbingTailpieceA tailpiece is the short straight pipe between a sink drain or faucet and the trap or supply connection.PlumbingTankless water heaterA tankless water heater heats water as it flows through, with no storage tank, firing only when a hot tap is opened.PlumbingTee fittingA tee is a fitting shaped like the letter T that joins a branch line to a main line.
W
PlumbingWater hammerWater hammer is the bang in the pipes when a valve shuts quickly and the moving water stops all at once, sending a pressure wave down the line.PlumbingWater heater drain panA drain pan is a shallow pan under a tank water heater that catches leaks and drains them away.PlumbingWater pressureWater pressure is the force of the water in the supply lines, measured in pounds per square inch with a gauge on a hose bibb or test port.Shared with Water Treatment and WellWater softenerA water softener removes the minerals that make water hard by trading them for sodium or potassium on a resin bed, which it recharges with salt.Shared with Water Treatment and WellWell pumpA well pump lifts water from a private well into the house, either submerged down the well or as a jet pump above ground.PlumbingWet wallA wet wall is a wall that holds the drain, vent and supply pipes for the fixtures along it, often built thicker than a normal wall to fit the pipes.Shared with Property MaintenanceWork orderA work order is the document that authorizes a job and records what was done: the request, location, tasks, parts, time and sign off.
More for plumbers: free plumbing tools, templates and guides and how the trade runs on Koira. Or browse the whole glossary.