Boiler loosing pressure question.

Hi All,

I’m having some problems with my Combi Boiler. It keeps loosing pressure, every 24 hours or so it goes from about 2.5 bar down to 0.

I’ve had a plumber investigate the boiler and he tells me there is no issue, and that it is likely there is a leak in the system somewhere, no leak can be spotted but there is one area where pipes are concreted into the floor (part of a new extension that is less than 12 months old), Obviously this is a strong contender for the where a leak might occur, as water hasn’t been spotted anywhere yet so it is unlikely to be anywhere visible. However last night while attending to my 6 month old I noticed that the radiator in her bedroom was warm and was on at 3:00 a.m. no other radiators were on in the house and neither was the heating. So there are 2 questions for the experts.

1) Why would the heating in one radiator come on in the middle of the night when the heating was not set to come on and no other radiators were on?
2) Could the radiator coming on be the source of our loss in pressure?

Many thanks for any advice offered as this is driving me up the wall (the boiler is in the loft so it is a real pain to keep re-filling!

what combi is it?

does it have a frost stat

why do you fill it up to 2.5?

is the pressure relief valve dripping (look out side and you should see a pipe that has been turned back to face the wall)

Did the plumber chap check the expansion vessel?

I thkni it is a Baxi something, and the plumber did check all of the above, he fitted a ne expasnion vessel when the extension was done. Ther ecould be a frost protector thing that may kick in but I can't understand why only 1 rad would come on?

Fat fingers sorry!

Also I only fill the boiler to 2.0

And the overflow thing doesn't appear to be leaking, the plumber checked the pipe at the boiler end and said it was dry.

We had a problem with our combi last year. We kept having to top up the system with water to keep it at least 0.5 bar, but when it was switched on it was going up to 2/2.5 bar for a couple of weeks before shooting up to 3.2bar very shortly thereafter. After a week's process of elimination by our engineer (who kindly charged us £15 for 3 visits!), it turned out to be an air leak in the expansion vessel - not the cheapest thing to replace, but it did the trick!