pressure loss on combi boiler

12 Nov 2007
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United Kingdom
Please can someone help with a problem that is driving me mad!!
I have a Ferroli combi boiler which is losing pressure.

It has had the expansion vessel checked, is not losing water from the prv and has recently has a new aav. It will lose pressure from 2 bar down to 1 bar overnight occasionally.

I will then top it up and pressure may stay unchanged for a week but other times will fall slowly over a week.

I assume it is a leak but why would pressure loss fluctuate like this.

Could it be anything else ?

I just need to be sure as the pipes are all under concrete floors!!

Thanks for your help
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Probably to do with temperature of the pipes at the point where its leaking from (some leaks get worse as the pipe or fitting expands and some get worse when it cools down) To have to top up like this is bad news as you probably have no inhibitor left in the system. Is there no damp patches anywhere ?
thanks for the reply.

No there are no damp patches anywhere.

Looks like I will have to get specialist firm out to find it
Dont know how much these firms charge but might be worth getting estimate to re-pipe, good luck.
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I have the same problem , but iv tracked it down to a leaking secondary heat exchange ,iv just put a new seal kit into it but still loss of pressure, it look like a new one ,but they cost around £200/£250 not good ! very easy to put in/out . see how much water is running out of the condencing pipe over night/day when not in use if theres a cup full or so id start looking there !

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