Check these first, whatever the brand
- Read the gauge when the heating is cold
Pressure rises as the water warms up, so check it with the heating off and the boiler cool. Many boilers want about 1 to 1.5 bar; your manual gives the exact range.
- Top it up with the filling loop
Follow your boiler's manual: open the filling loop valves slowly, watch the gauge, and close them fully when it reaches the right pressure. Don't go past the maker's figure.
- Reset the boiler
Once the pressure is back up, reset the boiler the way your manual describes.
- Bled a radiator recently?
Bleeding radiators lets air out and lowers the pressure, so a top-up afterwards is normal.
- Look for a leak
If it keeps dropping, check radiators, valves and the pipes under the boiler for drips. Also look at the small pressure relief pipe outside: if it drips, the boiler is letting water out.
When it's time for an engineer
If you have to top up more than now and then, something is losing water. A Gas Safe engineer will check the expansion vessel, the pressure relief valve and the system for leaks.
Parts people end up buying
Only once the checks point to a part. Match it to your model number: it's on a label on the data badge, usually under the boiler or behind the front cover.
- Radiator bleed keySearch on Amazon
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Questions people ask
What should my boiler pressure be?
Most boilers want about 1 to 1.5 bar when the system is cold, but check your manual: some makers give a wider range.
Why does my boiler keep losing pressure?
Usually a small leak somewhere in the system, or a fault with the expansion vessel or the pressure relief valve. If you're topping up often, have it checked.