possible causes of boiler pressure dropping

[Londoncalling]

Grrrrr , with AA for boiler insurance for two years but pretty sure they are going to get out of this one as in two years of payment ive never had that "initial inspection" so likely void for first issue

Anyways to the issue , i have sealed system with a "loop" pipe , turn thr knob pressure goes up , however last week "pressure "has started going down every couple of days , meaning top up required

any ideas ?

[John Rumm]

Either, a leak, or, a failed / discharged expansion vessel.

The former is self explanatory ;-) The latter is a little more subtle.

See the sealed system FAQ for chapter and verse:

[Tim+]

Water's leaking out. ;-)

That maybe a simple repair like a leaking radiator valve gland or it could be a knackered heat exchanger or anything in between.

First thing to check is to see if any water is coming out of the blow off valve by the expansion vessel. A common cause of pressure loss is expansion vessel failure which means that water is expelled from the system when boiler warms up (after a top-up) as there's no expansion capacity left in the system.

If the expansion vessel has failed it's easy to add a new one to the system.

Tim

[Dave Liquorice]

Don't let 'em if they have never contacted you for the inspection that is their problem not yours. If they do try to wriggle they have taken your premiums under false prentences, get them refunded...

There is a leak some where. It might be a right bar steward to find or could simply be a gland on a valve that has objected to the summer and doesn't want to play any more. Also check the pressure relief valve, they can get a bit of crud in and not close properly. But of course the AA will do that for you.

[R D S]

I had this going on for years then a temp sensor packed in and since replacing it's been steady.

I'd checked all the fittings at the rads but had never thought too look in the boiler as there were no visible leaks, I guess it was leaking slowly enough to evapourate.

[RJH]

Apparently, and this is from the dark recesses, if the fault would have arisen inspection or no, a claim can be made.

Rob

[Phil L]

Check each valve on each radiator - one of mine leaked slightly but it was at the side of a sofa and the small puddle was completely out of view, check the carpets below each rad for signs of dampness, look on ceilings and near pipe boxes for signs of damp that have not been noticed before....in other words, water is getting out somewhere.

[John Rumm]

A plastic bag elastic banded onto the over pressure relief pipe will tell you if it is there...

[Londoncalling]

thanks guys

you have gave me a few things to chase there