Central heating and boilers explained

Did you know your home’s plumbing system determines the taps, shower and radiators you buy? Choosing a product that isn’t compatible with your water pressure could affect its performance. After all, there’s nothing worse than a shower with no power.

So, before you start shopping for a bathroom, you need to understand the type of plumbing system you have, as it’s this that will dictate whether the water pressure is high or low. You can use our handy guide to the main types to get started (but check with your plumber if you’re in any doubt).

Mains system

In a mains water system, your water comes from an unvented hot water cylinder that is fed directly from the cold mains water feed. This will deliver hot water at mains pressure, which tends to be high (1 – 3bar), and hot water is stored until it’s needed.

Combination boiler

A combi boiler provides hot water on demand from the mains. It takes up less room than other systems because you don’t need a cold water tank or hot water cylinder. Water pressure is dependent on the age and size of the combi boiler, along with the pressure of the mains water. A 28kW combi boiler will typically provide between 1bar and 1.5bar pressure.

Gravity-fed system

Older properties tend to have gravity-fed systems, where a large cold water tank in the loft feeds a hot water cylinder somewhere else in the house, such as in the airing cupboard. The water pressure and flow will tend to be low (around 0.2bar).

Pump assisted system

Low-pressure gravity-fed systems can be boosted with a pump, resulting in anything between 1.5bar and 4bar pressure. There are two types: a shower pump and a universal pump. If you have a shower less than 600mm from the cold water tank, this is known as a negative head system and you’ll need a universal pump. However, if the shower is more than 600mm from the tank, this is a positive head system and you can use a standard shower pump.