Boiler pressure too high? Help!!

kandy91

Hi the pressure on my combi boiler is really high,it's between 3-4 (should be 1-1.5). After reading online I bled the radiators and the pressure came down right away and I was able to get the heating on with no problems. I checked it about half an hour later and it's went back up to just below 4! I'm really not sure what to do now as we're homeowners and don't have any money to call someone out! I'd be grateful if anyone could give any suggestions as to what I can try.

TIA

BristolS

Disconnect the filling loop, it might be passing

kandy91

how do I do that? I know nothing about boilers.

Nikkster

Did the pressure go up after you put the heating on? When the boiler is running, the pressure will and should go up, then return to the 'normal' range once the boiler has cooled down (this won't be immediate, will take a little while).

kandy91

It did yes,but it never goes up that high. It's been turned off now for about 45 minutes and it's not went back down to normal.

bridgedino

Your expansion vessel has either lost is charge or is broken

cajef

Sounds like the expansion vessel needs re-pressurising.

kandy91

Is that something I can fix myself?

cajef

kandy91 wrote: »

Is that something I can fix myself?

No, the boiler needs servicing, if it is gas then by a Gas Safe registered boiler engineer.

Ectophile

There's two likely possibilities:

1. Boiler is constantly filling through the refilling hose because the valves aren't closed properly.
2. Expansion vessel has failed.

It should be easy to work out which of the two it is. If the pressure is way too high when the boiler is on, but drops down again once the heating is off and the system has cooled down, then it's the expansion vessel. That's a job for a heating engineer to fix, either by replacing the existing one, or adding a second one.

If the pressure just keeps going up even when the boiler is off, then it's the refilling pipe. Look for a flexible hose under the boiler. Depending on the system, it may just be a hose with a tap on each end in the pipework near the boiler, or it may be tucked up inside the boiler. There will be a valve on each end. Make sure that both are turned off. If that still doesn't work, the hose should just unscrew from the valves so you can remove it entirely. Have a container handy to catch any water that spills out while you do that. If one of the valves starts dripping, it will need to be replaced.