Glossary
Plumbing glossary
34 plumbing terms in plain language. Use it to follow a plumber's explanation or to read a quote. Updated .
A
- Anode rod
- A metal rod inside a tank water heater, usually magnesium or aluminum, that corrodes in place of the steel tank. When it is used up, the tank itself starts to rust. Learn more about anode rod
B
- Backflow preventer
- A valve assembly that stops water from flowing backward from a property into the public water supply. Irrigation systems and some fixtures are required to have one, and many cities require yearly testing.
- Backwater valve
- A one-way valve on a building's sewer line that closes if sewage flows back from the street, protecting basement fixtures during sewer surcharges. Learn more about backwater valve
- Ball valve
- A shutoff valve with a lever handle that opens or closes with a quarter turn. The handle in line with the pipe means open; across the pipe means closed. Learn more about ball valve
- Belly (sag)
- A low section in a sewer line where the pipe has settled. Water and waste collect in it and cause repeated blockages. Lining cannot correct a belly; the section has to be re-laid. Learn more about belly (sag)
C
- Cleanout
- A capped access point on a drain or sewer line, usually near where the line leaves the house, that lets a plumber run a cable, jetter or camera into the pipe.
- Closet auger
- A short, hand-cranked cable with a protective sleeve, made for clearing clogs in a toilet's trap without scratching the porcelain. Learn more about closet auger
- Combined sewer
- A sewer system that carries storm water and sewage in the same pipes. In heavy rain it can fill and push sewage back into basements. It is common in older cities in the Northeast and Midwest.
- CPVC
- Chlorinated polyvinyl chloride, a rigid cream-colored plastic pipe approved for hot and cold water supply. It becomes brittle with age and can crack if frozen.
- Cured-in-place pipe (CIPP) lining
- A trenchless repair in which a resin-soaked liner is pulled or inverted into an old sewer pipe and hardened to form a new pipe inside it. Learn more about cured-in-place pipe (cipp) lining
D
- Dip tube
- The plastic tube that carries incoming cold water to the bottom of a tank water heater. If it breaks, cold water mixes at the top and hot water runs out quickly. Learn more about dip tube
E
- Expansion tank
- A small pressurized tank on the cold line above a water heater that absorbs the extra volume created when water is heated in a closed plumbing system. Learn more about expansion tank
F
- Fill valve
- The valve inside a toilet tank that refills the tank after a flush and shuts off when the water reaches its set level. Learn more about fill valve
- Flapper
- The rubber seal at the bottom of a toilet tank that lifts to release water for a flush. A worn flapper lets water leak into the bowl and makes the toilet run. Learn more about flapper
G
- Galvanized pipe
- Steel pipe coated with zinc, used for water supply until about the 1960s. It corrodes from the inside, which lowers pressure and discolors water. Learn more about galvanized pipe
- Gate valve
- An older style of shutoff valve with a round wheel handle that takes several turns to close. Gate valves often seize or fail to close fully after years without use. Learn more about gate valve
H
- Hose bib
- An outdoor faucet with a threaded spout for a garden hose. Also called a sillcock or spigot. Learn more about hose bib
- Hydro jetting
- Cleaning a drain or sewer line with water at high pressure, typically 1,500 to 4,000 psi, to remove grease, scale and roots from the pipe wall. Learn more about hydro jetting
L
- Lateral (sewer lateral)
- The pipe that carries wastewater from a building to the public sewer main. In most cities the property owner owns and maintains it. Seattle calls it a side sewer. Learn more about lateral (sewer lateral)
- Lead service line
- A water service pipe made of lead, installed in many US cities until it was banned in 1986. Utilities are replacing them because lead can enter drinking water.
M
- Main shutoff valve
- The valve that stops all water entering a building. It is normally found where the water line enters the house, near the meter or the water heater. Learn more about main shutoff valve
P
- P-trap
- The U-shaped bend of pipe under a sink or other fixture. It holds water that blocks sewer gas from entering the room, and it is where many clogs collect. Learn more about p-trap
- PEX
- Cross-linked polyethylene, a flexible plastic tubing used for hot and cold water supply. It resists scale and tolerates freezing better than rigid pipe. Learn more about pex
- Pipe bursting
- A trenchless method of replacing a sewer or water line by pulling a new pipe through the old one while a bursting head breaks the old pipe apart. Learn more about pipe bursting
- Polybutylene
- A gray flexible plastic water pipe installed from about 1978 to 1995, often stamped PB2110. It becomes brittle and fails without warning, and is usually replaced. Learn more about polybutylene
- Pressure-reducing valve (PRV)
- A valve on the main water line that lowers incoming street pressure to a safe level for the house. Plumbing codes call for one when pressure exceeds 80 psi. Learn more about pressure-reducing valve (prv)
S
- Slab leak
- A leak in a water or drain pipe that runs beneath or within a concrete slab foundation. Learn more about slab leak
- Sump pump
- A pump in a pit at the lowest point of a basement or crawl space that removes groundwater before it can flood the space. Learn more about sump pump
T
- Temperature and pressure relief (T&P) valve
- The safety valve on a water heater that opens if the tank gets too hot or pressure gets too high. It must never be capped or plugged. Learn more about temperature and pressure relief (t&p) valve
- Thermocouple
- A sensor in a gas water heater that detects the pilot flame and keeps the gas valve open. When it fails, the pilot will not stay lit. Learn more about thermocouple
- Trenchless repair
- Any method of repairing or replacing a buried pipe without digging a trench along its length, mainly pipe lining and pipe bursting. Learn more about trenchless repair
V
- Vent stack
- A vertical pipe that runs through the roof and lets air into the drain system so water flows freely and traps keep their water seal. A blocked vent causes gurgling and slow drains.
W
- Water hammer
- The banging noise in pipes when a valve closes quickly and moving water stops suddenly. Arrestors and lower water pressure prevent it. Learn more about water hammer
- Wax ring
- The wax seal between the base of a toilet and the drain flange in the floor. When it fails, water or sewer gas escapes at the base of the toilet. Learn more about wax ring
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