Last autumn I put in a Vaillant combi, over the winter it needed weekly
topping up and I have not found any leaks. Still none the wiser and now the
rads have shut off, another clue presents itself.
Now the boiler doesn't need topping up as often in fact it's been months
since I did it last. I'd have thought there would be no change. I mean the
whole system is still under the same pressure isn't it? Does it point to
knackered expansion vessel? And no, the PRvalve is not weeping one bit.

--
Mike W

On Thu, 31 May 2007 22:36:26 GMT, "visionset"
wrote:

Last autumn I put in a Vaillant combi, over the winter it needed weekly
topping up and I have not found any leaks. Still none the wiser and now the
rads have shut off, another clue presents itself.
Now the boiler doesn't need topping up as often in fact it's been months
since I did it last. I'd have thought there would be no change. I mean the
whole system is still under the same pressure isn't it? Does it point to
knackered expansion vessel? And no, the PRvalve is not weeping one bit.

Two Tests

Put the system on for a while to heat right up and then see if any
pressure loss when cool.

Then empty the smallest rad, (bathroom?), and then repressurise and
heat up again. When it cools see if any pressure has been lost as
usual.

The empty rad will act as an expansion pressure vessel and no pressure
loss will point to a defective one in the boiler.

In message , visionset
writes
Last autumn I put in a Vaillant combi, over the winter it needed weekly
topping up and I have not found any leaks. Still none the wiser and now the
rads have shut off, another clue presents itself.
Now the boiler doesn't need topping up as often in fact it's been months
since I did it last. I'd have thought there would be no change. I mean the
whole system is still under the same pressure isn't it? Does it point to
knackered expansion vessel? And no, the PRvalve is not weeping one bit.

Sounds like the leak is scaled up and is waiting for xmas eve to start
again

--
geoff

Sounds like the leak is scaled up and is waiting for xmas eve to start
again

PMSL

On Thu, 31 May 2007 22:36:26 +0000, visionset wrote:

Last autumn I put in a Vaillant combi, over the winter it needed weekly
topping up and I have not found any leaks. Still none the wiser and now the
rads have shut off, another clue presents itself.
Now the boiler doesn't need topping up as often in fact it's been months
since I did it last. I'd have thought there would be no change. I mean the
whole system is still under the same pressure isn't it? Does it point to
knackered expansion vessel? And no, the PRvalve is not weeping one bit.

The chances are that there is a tiny leak on a joint or valve which is
only present when the water is hot. Since the topping up was only weekly
it's quite possible that the size of the leak could have gone unnoticed,
especially when the pipes were hot causing and leakage to evaporate.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards