GETTA Help
Boiler losing pressure: common causes
A small pressure change can be normal, but repeated pressure loss usually means the heating system needs attention. A water leak, a radiator issue, or a boiler component may be involved.
Safe observations to make
- Record the pressure when the system is cold and again when it is warm.
- Look for visible drips around radiators, valves and accessible pipework without opening the boiler.
- Check whether radiators were recently bled or other heating work was carried out.
- Note any fault code and how quickly pressure falls.
Possible reasons
Pressure can fall when water leaves the sealed heating system. That may be through a small leak, after radiator bleeding, or because an expansion vessel, pressure-relief valve or another component is not working correctly. Only an inspection can establish the cause.
Repressurising is not a diagnosis
Some manufacturers describe a user procedure for topping up pressure. Follow only the instructions for your exact boiler if they clearly identify it as a normal user control. Do not remove covers, guess which valves to operate, or repeatedly top up a system that keeps losing pressure.
When professional help is appropriate
Contact a suitably qualified Gas Safe registered engineer if pressure repeatedly drops, a leak is visible, the boiler stops working, or you are unsure how to use the controls. Share the pressure readings, timing, fault codes and any recent work.