A boiler usually loses pressure because of a small water leak, recently bled radiators, a faulty pressure relief valve or a problem with the expansion vessel. While topping up the pressure may restore your heating temporarily, repeated pressure loss often indicates an underlying fault that should be inspected by a Gas Safe engineer.

Most boilers should read between 1 and 1.5 bar when the heating system is cold. When the heating is running, the pressure will naturally rise slightly, usually to around 2 bar. Always refer to your manufacturer's instructions, as recommended operating pressure can vary slightly between models.

Yes, in most cases homeowners can safely repressurise a combi boiler using the filling loop. However, you should only increase the pressure to the recommended level, usually around 1–1.5 bar. If you're unsure or the pressure keeps dropping afterwards, it's best to arrange a professional inspection.

Bleeding radiators removes trapped air from your heating system, which also reduces the water pressure. This is completely normal. Once you've finished bleeding all radiators, simply repressurise the system back to the recommended level before restarting your boiler.

Yes. If the pressure falls too low, many modern boilers automatically shut down to protect the system. This can leave you without heating or hot water until the pressure is restored.

It's a good idea to check your boiler pressure every few weeks, especially during winter when your heating is used more frequently. You should also check the pressure after bleeding radiators or if you notice your heating isn't performing as expected.

Yes. Any leak within your heating system, whether from the boiler itself, pipework or radiators, can gradually reduce pressure over time. Even a small leak may eventually cause your boiler to stop working properly if left unrepaired.

You should contact a Gas Safe engineer if your boiler continues losing pressure after repressurising, you notice water leaking from the boiler, the pressure drops repeatedly within a few days or your boiler displays recurring fault codes. These symptoms often indicate a fault that requires professional diagnosis and repair.

A very small drop in pressure over several months can be normal. However, if you find yourself regularly topping up the pressure, there is likely an issue that should be investigated.