When discussing the problem with your plumbing system, many plumbers will use terms you’re unfamiliar with, and often, too shy to ask what they mean!  Our team of expert plumbers pride themselves on explaining the problem, and how we’ll fix it as clearly as possible… and in your own (jargon-free) language!

Though, you will often hear us use a few terms that might leave you searching for the nearest dictionary. So we’ve put together an outline of plumbing terms, and what they actually mean, to keep you fully in the loop with your plumbing problems…


A fitting that joins two different types of pipe together.


The part at the end of a tap spout, which mixes air into the running water, aerating it.

Air Gap

An air-filled space which allows contaminated water to be discharged,  preventing it from flowing back into the potable water supply.


Trapped air in pipework that is unable to escape naturally, resulting in a poor flow along the pipe.

Back siphonage

The reverse flow of water caused by siphonage, which can lead to a contamination of your water supply.

Back-to-wall cistern

A cistern separate from the toilet which might be concealed behind a wall or within fitted furniture.

Ball cock 

The valve which controls the flow of water into your  cistern


The unit of measurement of water pressure – one bar is approximately equivalent to a column of water 10m high or 14.5 lbf/in² or 100 kPa (kilopascal).

Bleed valve

The air release valve used to release air from your central heating system. You’ll find it on your radiator. (See: How to bleed your radiator)

Check valve

A plumbing fitting that allows water flow in one direction only.


The fixed container that holds water at atmospheric pressure, normally applied to the local water storage to flush your toilet.
Combination boiler (AKA “combi”)

A boiler which combines both a central heating water heater and a domestic water heater in one unit. Unlike an vented heating and hot water system, a combi does not store hot water, it heats water as and when you need it.

Deck mounted taps

Taps designed to sit on the edge of the basin or bath, rather than being wall mounted.

Dynamic pressure

The pressure rate when the water is flowing

Earth bonding 

A legal safety requirement to have all metal parts within a plumbing system connect to earth, preventing them from being dangerous.

Electrical heating element

A feature used in electric showers to heat the water as it flows through.

Grey water

The waste water from your bath, sink, washing machine, dish-washer etc., which has been used and is considered to be only mildly dirty.

Mixer shower / taps

A shower or tap using a valve to combine hot and cold water. You’ll adjust the two until you get the temperature and flow you like.

Monobloc taps

A mixer tap for a single mounting hole. The input pipes are smaller than ‘normal’ taps.

Overflow pipe

A pipe connected from a tank or cistern to get rid of any surplus water safely, without causing damage. This will usually kick in when there is a fault (i.e. a leaking valve etc).

Pressure balance valve

A shower mixing valve that maintains the balance between hot and cold water by immediately regulating fluctuations in pressure. This keeps the temperature constant.

Servicing Valve

A valve for shutting off the water flow for servicing.

Static Pressure

The pressure rate when no water is flowing

Stop cock

A hand operated on/off valve allowing water flow in one direction.