If your boiler’s pressure gauge is below 1 bar, or it’s showing a low-pressure code (such as F22 on a Vaillant, E119 on a Baxi or F1 on an Ideal), you can usually fix it yourself in a few minutes.
What pressure should a boiler be?
With the heating cold, the gauge should read between 1 and 1.5 bar. It rises a little when the heating is on — that’s normal.
How to top up the pressure
- Turn the boiler off and let it cool
- Find the filling loop under the boiler — your manual shows where
- Slowly open the valve(s) and watch the gauge
- Close them when it reaches 1.2–1.5 bar
- Turn the boiler back on and reset it if needed
If the pressure keeps dropping
Pressure that keeps falling means water is escaping somewhere. Check under radiators, around valves and the pressure relief pipe outside. If you can’t find it, we can trace the leak for you.
Never open the boiler casing. If you smell gas, call the National Gas Emergency line on 0800 111 999 straight away.