Where's my leak? They say not the boiler, but I am not so sure.

ought74 · Feb 23, 2022

Good morning.

I have run another test. Initially I had 2 (out of 5) radiators turned off to stop the house getting to hot and the pressure never went above 2.7 bars, but there was also no dripping from the PRV pipe.

I then turned on all the radiators and the pressure briefly went up to 3.1 bars, then settled on 3 bars, and then the bag on the PVR pipe quickly collected water.

What conclusion does that lead to?

Thank you for your help and staying with me.

John.g · Feb 23, 2022

Start from scratch.
Are you just turning off the filling valve after topping up to 1 bar or are you also disconnecting the filling (flexible) line?. If just shutting the filling valve(s) water could still leak in, build up pressure leading to the PRV lifting. I would definitely disconnect the filling line to rule that out, for a start.
If no problems with above then problem definitely points to the EV (expansion vessel), it could have a punctured diaphragm resulting effectively in having no EV as it would be filled with water, it could also have a pre charge pressure far too high, maybe 2bar, if the pre charge pressure has fallen to 0 bar then the pressure would only have risen to ~ 1.7bar with 5 rads on but would have lifted the PRV at 3.0 bar with all rads on.

Guesswork is no good, get the EV checked out ASAP, I would then also get the PRV renewed as it might still dribble now that it has lifted numerous times, not worth taking the chance.

ought74 · Feb 23, 2022

I don't think it is slow pressure build up from the filling line as it doesn't go up unless I do it manually.

I have been in touch with the Energy supplier installation man, explained what I have done, and what you say it suggests, and he has agreed to come and sort us out with the boiler.

I fear though it might take about 8 weeks to eventually get the new boiler installed.