A loss of water pressure is a good indicator of some common issues that arise with boilers. Low pressure is relatively easy to diagnose, as most boilers have a built-in pressure gauge. Sometimes, it’s possible to correct water pressure yourself

Understanding water pressure

Constant water pressure is essential to the efficient functioning of your boiler system. Pressure in most modern combination boilers is maintained by cold water flowing from the water mains supply through a mechanism known as the ‘filling loop’[1].

What causes a drop in pressure?

A number of things can cause pressure to drop. It may be that there is a leak somewhere in your boiler system. Or, if you bled your radiators recently, it may be that pressure was lost then.

However, you may not be able to tell that you have a problem until you check the pressure gauge. A water leak, for instance, may be tiny and go unnoticed at first, only to develop into a larger problem down the line.

Checking your pressure gauge

Check the water pressure gauge or indicator, which is typically on the front of your boiler. For most boilers, this should be set around the 1 bar. The position set when the boiler was installed is sometimes shown by a red indicator needle.

If you have noticed repeated drops in your boiler pressure, make sure you check the gauge regularly. A drop in pressure is a good indication that there is a problem with your boiler.

How to tackle lost pressure

Each boiler will come with specific instructions about its pressure system. Check your user manual to see if you can re-pressurise your boiler yourself.

You may also find instructions on the rear of your boiler control panel. However, if your boiler panel needs tools to remove it, don’t touch it – book an engineer.

Likewise, if you continue to have pressure problems after re-pressurising your boiler according to the user manual, our expert engineers can diagnose and repair the problem. You don’t need to be a British Gas customer to book one-off boiler repairs for a fixed price.

Further reading

Central heating troubleshooting