Plumbing glossary

Cleanout — a capped fitting that lets a plumber get a snake or camera into the drain line without pulling a fixture. If your house lacks one, expect to pay more for main-line service, because the plumber may have to remove a toilet for access. P-trap — the U-bend under a sink that holds a water seal against sewer gas. A dry trap is the most common cause of a sewer smell in a rarely used bathroom.

GPM (gallons per minute) — flow rate at a fixture. WaterSense labeled showerheads use no more than 2.0 gpm versus a 2.5 gpm standard; WaterSense bathroom faucets use no more than 1.5 gpm against a 2.2 gpm federal maximum. GPF (gallons per flush) — toilet flush volume. The federal standard is 1.6 gpf, WaterSense labeled models are 1.28 gpf or less, and pre-1994 toilets used up to 6 gpf.

Expansion tank — a small tank that absorbs thermal expansion in a closed system. Pressure regulator (PRV) — a valve that reduces incoming street pressure to a level your plumbing can live with. Backflow preventer — a device stopping water from flowing backward into the supply. Hose bib — an exterior spigot; the frost-free type has the shutoff set back inside the heated envelope.

Hydro jetting — high-pressure water cleaning of a drain line, as distinct from snaking, which bores a hole through a blockage. Trenchless — sewer repair methods that avoid full excavation. Sanitary sewer lateral — the pipe from your house to the municipal main; in most places it's the homeowner's responsibility for at least part of its length, and where that responsibility ends is a local question worth asking your utility.

How to choose

Ask what a line item means before you approve it

No competent plumber minds explaining a term. Someone who's annoyed by the question is telling you something.

Learn 'cleanout' first

Whether your home has one directly affects the price of every future drain service call.

Know your lateral responsibility line

Where the homeowner's sewer responsibility ends and the utility's begins varies by city. Call your utility and ask — before there's a problem.

Use gpf and gpm to compare fixtures

These are standardized, published numbers, which makes them one of the few genuinely comparable specs in plumbing.