Slow leak underground heating system

Matt Simis

I have an outside Gas boiler (in garage) and pipes running from there to the house. Last year I pressurised it to 2bar and it developed a slowish leak (would have to top up pressure every 24hrs to keep it around 1bar).

During the summer it held 1bar when the heating was off. Now that I start using it again its started loosing pressure again. I cannot see/hear the leak or find evidence of it, so assuming underground (I didnt install any of this). I do not have time or money to start digging pipes out and relaying them.

So is there a really good leak sealer I could try? The couple I tried from B&Q didnt do much.

Buford T Justice

They'll do a better job at clogging up the system rather than actually stopping the leak tbh.

mad m

I heard that filling it up constantly will eventually rot the system with new fresh oxygenated water....

There is a company that will detect leaks in a system for you...Maybe get back the company that did it....

I have similiar problem, but not as bad as you. Got my hands on a thermal imaging camera and I seem to have found the leak with it outside, could see the heat coming up the path, I know its insulated but with the heat that the camera was showing it must be a leak....

sullzz

Matt Simis wrote: »

I have an outside Gas boiler (in garage) and pipes running from there to the house. Last year I pressurised it to 2bar and it developed a slowish leak (would have to top up pressure every 24hrs to keep it around 1bar).

During the summer it held 1bar when the heating was off. Now that I start using it again its started loosing pressure again. I cannot see/hear the leak or find evidence of it, so assuming underground (I didnt install any of this). I do not have time or money to start digging pipes out and relaying them.

So is there a really good leak sealer I could try? The couple I tried from B&Q didnt do much.

It doesnt sound like as if you have a leak , if the pressure didnt drop all summer it sounds fine , if you had a leak which was dropping a bar a day it would of happend over the summer regardless of your heat being on or off.
what could be happening is that your expansion vessell is gone and when your boiler is on the pressure relief valve is opening and releasing pressure,
check this , it may take a few mins to happen but when you turn your heating on monitor the pressure gauge and the safety valve discharge pipe , the pressure should rise to about 3bar pretty quickly
this may not be what the problem is but just something to check.

Avns1s

sullzz wrote: »

It doesnt sound like as if you have a leak , if the pressure didnt drop all summer it sounds fine , if you had a leak which was dropping a bar a day it would of happend over the summer regardless of your heat being on or off.
what could be happening is that your expansion vessell is gone and when your boiler is on the pressure relief valve is opening and releasing pressure,
check this , it may take a few mins to happen but when you turn your heating on monitor the pressure gauge and the safety valve discharge pipe , the pressure should rise to about 3bar pretty quickly
this may not be what the problem is but just something to check.

I agree, and it's definitely where I would be looking before trying to find a leak that may not exist.

mad m

Yeah agreed, but wouldnt he see a release from the expansion safety pipe if it gets to over 3bar? Wouldnt the heating shut down altogether due to high pressure and heat?

sullzz

mad m wrote: »

Yeah agreed, but wouldnt he see a release from the expansion safety pipe if it gets to over 3bar? Wouldnt the heating shut down altogether due to high pressure and heat?

The discharge pipe does not always shoot water out of it , it can sometimes just trickle water out , plus he said that the boiler is in his garage so the pipe could go through a wall out of sight
to the 2nd question , no .

Matt Simis

sullzz wrote: »

It doesnt sound like as if you have a leak , if the pressure didnt drop all summer it sounds fine , if you had a leak which was dropping a bar a day it would of happend over the summer regardless of your heat being on or off.
what could be happening is that your expansion vessell is gone and when your boiler is on the pressure relief valve is opening and releasing pressure,
check this , it may take a few mins to happen but when you turn your heating on monitor the pressure gauge and the safety valve discharge pipe , the pressure should rise to about 3bar pretty quickly
this may not be what the problem is but just something to check.

I actually thought of this too from Googling and seeing similar suggested last year. I asked the local Boiler Plumbing place and they said thats highly unlikely and a leak would be what Im describing as holding stationary cold water in a system at 1bar doesnt mean it can hold expanding hot water at nearly 3bar, which I thought was a logical counterpoint so left it.

I dont think it ever gets to 3bar, maybe 2.75ish. I will check it out though. I take it nothing at all should come out of the pressure vent pipe unless over.. 3.5bar? Also when you say the expansion vessel could be gone, in what manner?

sullzz

1 bar pressure is too much pressure to stay in a system without any drop if there is a leak
no water should ever come out of the safety valve pipe until the pressure reaches 3bar not 3.5bar.
the function of the expansion is to take the expansion of water within the heating system , the vessell has a diaphram in the middle with air on one side and the heating systems water on the other , when the diaphram breaks there is no more air for expandion so the safety valve opens to release the pressure .

Matt Simis

Well I can confirm that with no heat on at all over the last 2 days it lost pressure, from 1.5bar to virtually no pressure, so it definitely seems to be a leak which come back after the summer ended once the system was put in operation again. General gunk or dregs of leak sealer may have slowly created a poor seal on the leak which is why it held the minimal 1bar when not in use.

I also checked the expansion tank, it has 0.4bar pressure in it (confirmed air coming out not water). I tried topping it up to 1bar of air pressure which it held but didnt help the water loss situation.

mad m

Well if it is a leak, the only blessing it that you know its probably from garage to where it enters house. You sure its not inside? Have you a sub floor downstairs?

Or pipes under concrete...

heinbloed

The leak could be in the boiler as well. Esp. with condensing boilers such a micro leakage in the heat exchanger is hard to spot.
Isolate the boiler,empty/drain it and then pressurise it with air to see if it holds the air.

aah yes

If you find a leak and fix it, refill the system with rust inhibitor, Fernox MB1 5 litre tub.

andy2die4

most leaks of this type are at the boiler. You can test this by pumping up system to working pressure to appox 1.8 to 2.0 bar, then find your main flow and return pipes going into the boiler, close off both isolation valves and leave for 24hrs. If the pressure guage in the boiler drops, its the boiler. If it holds, slowly open the F & R valves and if it falls then its the pipes.