15 Common Plumbing Terms You Need to Know

If you live somewhere with a plumbing system (which you probably do), it’s worth having some basic knowledge of common plumbing terms.

If anything goes wrong with your system then the chances are that you’ll need to speak to a professional about it. This can be pretty tricky if they’re using terms and phrases you don’t understand. So here are 15 common plumbing terms you need to know.


When air is trapped in pipes, slowing down or stopping the flow of liquid.

Automatic air vent

A mechanical device that automatically releases air trapped in a water system. This is usually fitted at the highest point of a plumbing system.


When the flow of liquid is reversed and siphons back towards the source. This can often contaminate the source.

Ball cock

A valve used to control the flow of water into a cistern or tank. The valve is controlled by a float on the surface of the water in the cistern or tank.


The unit that you measure water pressure in.

Bleed valve

An air release valve you can usually find on radiators or at high points in pipework. You can use them to release air from your central heating system.

Check valve

A fitting designed to only let water flow in one direction.


A fitting that connects two pieces of pipe together.

Expansion tank

A tank that accommodates the expansion of water within a system as it heats up or absorbs pressure shock waves. This can be open or sealed depending on whether the system is vented or sealed.

Stack pipe

A tall, vertical vent pipe for the main waste pipe.

Stop cock

A hand-operated on/off valve, which allows water flow in one direction.

Thermostatic mixing valve

A water mixing device that automatically adjusts to temperature and pressure variations to maintain a selected temperature at the outlet. These are often fitted with showers or wash basins.


Part of a pipe that holds water to create a seal, stopping waste fumes from travelling back into a building. Examples of these include u-bends under toilets and p-bends and s-bends under basins and baths.

Vent pipe

A pipe that releases air or water from a hot water system.

Working pressure

The normal operating pressure that a faucet, valve or plumbing product is designed for.

So now you should know a few more handy plumbing terms. These should help you whenever you’re talking to a professional about your plumbing system. And remember, if they still use words or phrases that you don’t understand – just ask. The chances are that they’ll be happy to explain them to you.

Evy Coe

Evy works for Quotatis as a Content Marketing Executive. She loves to write about interior design and help homeowners with their DIY projects.