Plumbing glossary

Water supply fixture unit. A code value used to size water piping and meters.

Drainage fixture unit. A code value used to size drains and building sewers.

Pressure-reducing valve. Required when street pressure is too high for fixtures.

Cross-linked polyethylene made by the Engel method. Expansion fittings, high freeze tolerance.

Silane-method PEX. Stiffer, usually crimp or clamp fittings, common in production homes.

Medium-wall copper used for water supply. Still the benchmark for exposed and commercial work.

Cream or tan rigid plastic supply pipe. Gets brittle with heat and age.

Gray flexible supply pipe from the late 1970s–mid 1990s. Known failure risk.

Threaded gray steel supply. Corrodes from the inside and starves fixtures.

Traditional drain pipe. Lasts a long time, then scales and cracks, especially under slabs.

White plastic drain, waste and vent pipe. Standard for new drains above grade.

Black plastic DWV, more common in some older Texas tracts.

High-density polyethylene. Common for buried water service and some process lines.

A device that stops contaminated water from reversing into the potable system.

A tank that captures FOG from commercial kitchens before the sewer.

A water test of the drain system used to find leaks under a slab.

Temperature and pressure relief valve on a water heater. Must dump to a safe place.

A sacrificial rod inside a tank heater that slows corrosion. Hard water eats it faster.

How many gallons of hot water a tank can deliver in the peak hour.

The demand curve that turns fixture units into estimated peak GPM.

Responsible Master Plumber. The Texas license holder who is responsible for the work.

A counted list of pipe, fittings, fixtures and equipment from a drawing set.

Aligning multiple bids so they price the same scope.

Changing materials or routing to save money without hiding a cut in quality.

Routing new supply through the attic instead of under the slab. Common on Central Texas clay.