We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after
digging up trench under utility room radiator, there was no leak
there. Can anyone offer advise on how to make progress, or tips on
detection, cant keep on resetting boiler. Have only been in this
house 18 months and thought we were making progress up dating
utilities.

wrote:
We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after
digging up trench under utility room radiator, there was no leak
there. Can anyone offer advise on how to make progress, or tips on
detection, cant keep on resetting boiler. Have only been in this
house 18 months and thought we were making progress up dating
utilities.

It doesn't take a large leak to depressurise a CH system.

You could feed it a barium meal and go around with a geiger counter...

Is it possible to isolate sections of it at all?

wrote:
We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after
digging up trench under utility room radiator, there was no leak
there. Can anyone offer advise on how to make progress, or tips on
detection, cant keep on resetting boiler. Have only been in this
house 18 months and thought we were making progress up dating
utilities.

Have you watched the pressure gauge as the CH heats up? You may find it
it going up too high (i.e. 3 bar or more). If this is the case then the
pressure relief valve will probably open and vent some water outside.
Hence once it cools there is no longer enough pressure in the system.

You could tie a plastic bag under the blow off pipe to see if it
collects any water.

See the sealed system FAQ for information on pressure vessels:

http://www.makewrite.demon.co.uk/SealedCH.html

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

The Natural Philosopher wrote:
wrote:
We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after
digging up trench under utility room radiator, there was no leak
there. Can anyone offer advise on how to make progress, or tips on
detection, cant keep on resetting boiler. Have only been in this
house 18 months and thought we were making progress up dating
utilities.

It doesn't take a large leak to depressurise a CH system.

Well - to depressurise it every four hours must mean there's a
reasonable volume of water coming out in that time - ie measured in
pints rather than egg cups I'd have thought? Certainly enough to be
readily detected if it wasn't leaking some nefarious like under the
floor. I'm sure it would be coming through the ceiling, for example, if
there was a leak anywhere upstairs.

Where else is there pipework which you can't eyeball? When you say
you've dug a trench in the utility room floor do you mean you've exposed
all the buried pipework, or is there more?

If you can be convinced the leak is under there somehwere, one approach
might be to bypass the under-floor bit by running new pipes above ground
somewhere - less attractive but less invasive??

David

On Wed, 26 Dec 2007 07:51:08 -0800, paulanderika wrote:

We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after digging
up trench under utility room radiator, there was no leak there. Can
anyone offer advise on how to make progress, or tips on detection, cant
keep on resetting boiler. Have only been in this house 18 months and
thought we were making progress up dating utilities.

There is a FAQ for this. See below.


--
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

You could feed it a barium meal and go around with a geiger counter...

Barium sulphate, as given by mouth or as an enema is radio-opaque
to X-rays, not radio-active.

--
Graham

%Profound_observation%

In an earlier contribution to this discussion,
wrote:

We have a new combi boiler, installed in May, now losing all water
pressure about every 4 hours and shutting down. We have been advised
there must be a large leak under our concrete floors but no sign is
really showing. Utility and kitchen floors appear damp but after
digging up trench under utility room radiator, there was no leak
there. Can anyone offer advise on how to make progress, or tips on
detection, cant keep on resetting boiler. Have only been in this
house 18 months and thought we were making progress up dating
utilities.

There may not be a leak at all from the pipework. It is quite possible that
the expansion vessel has lost its air/nitrogen charge so that the water in
the system cannot expand when it gets hot without building up an excessive
pressure which causes the pressure relief valve to open - and water to be
expelled outside the house. Then, when the system cools again, the water
contracts and all pressure is lost.

Find the discharge pipe, and hang a container under it and see whether it
collects any water.
--
Cheers,
Roger
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