"Andrew Mawson" wrote in message news:...

I have a combi boiler feeding two small holiday cottages. Total of two
large radiators, two small radiators, two showers and kitchen sinks. There
had been a history of loss of pressure, so when the cottages were renovated
and the floors taken up (suspended floor) every joint was checked and there
was no evidence of leakage or staining so the floor was re-laid and tiled.
Everything pointed to the Worcester 20-25 boiler which had other problems
(it had already had it's expansion vessel, safety pressure valve and auto
air vent changed).
Symptoms were that if the boiler stayed warm it was ok but if allowed to go
cold (power cut for example) the pressure would go to zero, no sign of any
pressure on the gauge what so ever.

So we had the boiler replaced (Grant Vortex 21 combi). Then we had a power
cut, and ARGH !!!!!! the pressure fell to zero. Re-pressurised and it was
ok for a few days - then the oil control solenoid failed (infant
mortality?), the boiler went cold, and again the pressure went to zero
indicated on the gauge. Last night again a repeat - system not working as
no pressure this morning - (it was fine when I checked it at 20:00 last
evening).

So logically the leak is most unlikely to be the new boiler as the symptoms
are pretty well identical to the old one, which begs the question, how can
a leak suddenly develop, allow total loss of pressure, yet seal fine when
the system is topped up and show no evidence?

Andrew

After a huge amount of faffing about I think we've found the leak

We put isolator valves in the two 'flows' and common 'return', blanked off
the riser pipes to each end of all the radiators, and pressurised each run
having a gauge on to see pressure drop. Nothing, zilch, no leaks !

So when everything else has been eliminated, Sherlock tells us what remains
MUST be the problem. So a very close look at the brand new boiler eventually
reveals that the flexible pipe to the integral expansion vessel is leaking
at it's 'tap connector' Dismantling shows the rubber washer to be graunched
in two, presumably in the factory, and is leaking when cold, but sealing
when hot. Exactly the same symptoms as the previous boiler showed, but in
this case the leak seems to have been into the combustion chamber from the
water jacket. Early days yet, but it does seem we've bottomed this one after
a lot of heartache

Andrew

"Andrew Mawson" wrote in message

After a huge amount of faffing about I think we've found the leak

We put isolator valves in the two 'flows' and common 'return', blanked off
the riser pipes to each end of all the radiators, and pressurised each run
having a gauge on to see pressure drop. Nothing, zilch, no leaks !

So when everything else has been eliminated, Sherlock tells us what
remains MUST be the problem. So a very close look at the brand new boiler
eventually reveals that the flexible pipe to the integral expansion vessel
is leaking at it's 'tap connector' Dismantling shows the rubber washer to
be graunched in two, presumably in the factory, and is leaking when cold,
but sealing when hot. Exactly the same symptoms as the previous boiler
showed, but in this case the leak seems to have been into the combustion
chamber from the water jacket. Early days yet, but it does seem we've
bottomed this one after a lot of heartache

Andrew

Glad you've got it sorted!

Tim

On Wednesday, March 5, 2014 11:02:51 AM UTC, Tim+ wrote:

Glad you've got it sorted!

Ditto.
Let us know if it does prove to be the only leak.
I'd have expected you'd have noticed that volume of water inside the boiler casing, unless it's evaporating or going down the condense drain somehow.

"Onetap" wrote in message
...

On Wednesday, March 5, 2014 11:02:51 AM UTC, Tim+ wrote:

Glad you've got it sorted!

Ditto.
Let us know if it does prove to be the only leak.
I'd have expected you'd have noticed that volume of water inside the
boiler casing, unless it's evaporating or going down the condense drain
somehow.

Thanks chaps.

I took the opportunity to measure what volume needs releasing to go to zero
pressure, and it's a whopping 950 mL, so I too would have expected to see a
big puddle. When the installer fitted the new boiler he had a bit of a
whoops moment in that the vertically mounted manual air vent (as is usual)
held onto it's rubber seal until the last second, let go and then produced a
fountain. This descended though the boiler, so things were rather damp
anyway

I feel sorry in a way for the chap as he's been back and forth like a yo-yo
for two issues that were manufacturer induced (the o/c oil coil and this
leak) and he reckons he'll get no sympathy from the makers (Grant)

Andrew

On 05/03/2014 09:13, Andrew Mawson wrote:
"Andrew Mawson" wrote in message news:...


So when everything else has been eliminated, Sherlock tells us what
remains MUST be the problem. So a very close look at the brand new
boiler eventually reveals that the flexible pipe to the integral
expansion vessel is leaking at it's 'tap connector' Dismantling shows
the rubber washer to be graunched in two, presumably in the factory, and
is leaking when cold, but sealing when hot. Exactly the same symptoms as
the previous boiler showed, but in this case the leak seems to have been
into the combustion chamber from the water jacket. Early days yet, but
it does seem we've bottomed this one after a lot of heartache

Andrew

Well done! It's so satisfying to get a "result"!

On Wednesday, March 5, 2014 1:17:33 PM UTC, Andrew Mawson wrote:

so I too would have expected to see a

big puddle.

Possibly the graunched-up washer was also blocking or restricting flow to & from the expansion vessel, making the PRV operate.
One of those irritating, obscure problems that you only recognise once you've fixed it.
Fingers crossed.

"Onetap" wrote in message
...

On Wednesday, March 5, 2014 1:17:33 PM UTC, Andrew Mawson wrote:

so I too would have expected to see a

big puddle.

Possibly the graunched-up washer was also blocking or restricting flow to &
from the expansion vessel, making the PRV operate.
One of those irritating, obscure problems that you only recognise once
you've fixed it.
Fingers crossed.

No definitely no water been escaping from the PRV - it has 'birthday'
balloon installed on it's pipe as a tell tale, a handy tip I picked up
somewhere Sad person that I am I've rigged an ip camera up looking at the
pressure gauge !

So far it's all working fine with everything back to normal. This fault has
been giving us grief for two years so I sincerely hope we've now seen the
end of it.

Andrew