Combi boiler pressure and a leaking pipe

bouicca21

I am currently dealing with builders about damage caused by leaking central heating pipes. Two leaks were identified and repaired 3 weeks ago. I now have drying equipment.

Initially the pressure in the combi boiler was rock solid so after a few days I stopped checking it. Today I discover that the pressure has fallen back. It was a fraction under 2 bar, now it is 1.5.

Does this suggest there is another leak? Maybe more of a weep than a full on leak? It seems a big drop in just 3 weeks.

I can't face going through all the disruption again, so I want to be absolutely sure before the floor gets reinstated.

Le_Kirk

If it was a full-on leak I would expect to see it reduce to zero. When it was 2 bar, was the system hot and did you check it when it was cold? This might account for the difference.

JohnB47

In my experience, when you recharge a system with a large amount of water, the initial few bursts of central heating produce gas in the system. This gas is easier compressed compared to water, so the pressure falls. You need to bleed the rads and then recharge a few times and then monitor the pressure. If you don't have a leak, the pressure should settle after doing this about three times.

bouicca21

I haven't run the heating at all but presumably it has all filled up again. So I will bleed the radiators and see what happens!

Thanks.

southcoastrgi

2 bar is too high anyway, the prv might have opened when you used it dropping the pressure & it might continue to drip, tape a freezer type bag over the copper pipe outside & see if it gets water in it

JohnB47

bouicca21 wrote: »

I haven't run the heating at all but presumably it has all filled up again. So I will bleed the radiators and see what happens!

Thanks.

Sorry, you've lost me there - "presumably it has all filled up again"?

I would bleed the radiators and re pressurise to 1.5 bar - no more. Then monitor it. You might have some docs that came with the boiler that would state what the pressure should be - or quote the boiler make and model and experts here will tell you.

However, if you haven't run the central heating at all, could be you do have a leak, either in pipework or through the PRV as southcoastrgi says.

Personally, I would re pressurise and turn the central heating on for an hour. Next day, I'd bleed the rads, re pressurise to 1.5 again and turn heating on again for 1 hour. I'd do this sequence at least two times, maybe three and then leave the system off and monitor the pressure. This might be a pain but better to test the system 'under load' than just assume that all leaks have been fixed and then find out otherwise in the autumn when you really need the heating.

bouicca21

Ok will do. The manual says 1.5 bar. I did tell the track and trace people that, but they pressurised to nearly 2 bar anyway!

southcoastrgi

Just over 1 bar when cold & not working is the correct pressure for any sealed or combi boiler

southcoastrgi

bouicca21 wrote: »

Ok will do. The manual says 1.5 bar. I did tell the track and trace people that, but they pressurised to nearly 2 bar anyway!

They prob did that to try & find the leak but they should have then reduced it