Guide: how to re-pressurise your boiler

Every combination boiler has a pressure gauge, a small dial near the boiler controls. The system pressure should read between 1 and 1.5 on the scale. When pressure dips below 1, your central heating may stop working.

A drop in boiler pressure is the most common cause of heating system failures, but it is also among the simplest issues to resolve yourself. If you lack confidence doing this, our engineers can come and take a look.

Simple steps to re-pressurise your boiler

1. Check the pressure gauge. If the dial reads lower than 1, the pressure is insufficient and re-pressurisation is needed.
2. Turn off your system as a safety precaution.
3. Connect the filling loop. Inspect the pipework beneath your boiler. There should be two valves and a flexible silver pipe (the filling loop). Make sure both ends connect to each valve.
4. Release the valve to add cold water. Gradually open the valve using the handle (or a screwdriver or filling key if needed), watching the pressure gauge continuously.
5. Switch off the valves once pressure reaches 1 to 1.5. As soon as you reach the required pressure, shut off the valve.
6. Turn on your heating and verify it operates correctly. If not, contact an engineer.

Important notice

If you need regular pressure top-ups more than once a year, a system leak likely exists and needs professional inspection. Our team can help. See also our guide on the correct boiler pressure.