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

[ought74]

You can't change the PRV as you need to be gas safe qualified and resistered.

You can carefully note the pressure (cold) before topping up, tie wrap or tape a plastic bag around the PRV exit pipe, top up and again carefully note the top up pressure, when the pressure again falls the topping up pressure (cold), remove and carefully measure the water in the plastic bag.

I will try that tomorrow. Thanks. How much water would I expect for a 1/2 bar change?

 

[John.g]

Top up from 0.5bar to 1.0bar, 2.0litres (max) Just ensure the plastic bag can hold say 1 litre at least because if it fills up then the PRV is the problem.

 

[ought74]

I have run the experiment, once with a balloon on the PVR pipe, which didn't work very well, then a bag which leaked, and a third time more successfully.

I started at almost zero pressure topping up to 1 bar and in less than an hour (mostly with the heating on) the bag collected water. I left it longer but the level did not really rise much if any further.

I put the heating on for 2 spells with the system cooled down in between. After 3 hours the heating had gone off and the system cooled down again. The water pressure was about 0.2 bars and I had 400mls of water in the bag.

Do you think that is enough to be conclusive?

 

[John.g]

Yes, IMO, as long as the boiler pressure didn't exceed 2.8ish pressure which I'm sure you said it didn't/hasn't. Definitely, your fist port of call is to get the PRV renewed, and take it from there.
You might also get the exp vessel pre charge pressure checked as well while the boiler is de pressurized.

 

[ought74]

I am not sure if the pressure exceeded 2.8 when the heating was on, as I was not watching it. Is that important?

I do not really want to get the boiler fixed. I want to go back to the energy company boiler installer and tell them I was advised it was unlikely to be a system leak, and that I should run the test with the plastic bag, which shows that the PVR is at fault.

That will hopefully satsify them and then they will install the new boiler for me.

 

[John.g]

Yes, if the pressure reaches 3 bar or slightly less then it will lift the PRV, any pressure up to 2.6/2.7 is OK.

 

[ought74]

I see, thanks.

I will have to top the boiler up again, turn it on and watch for that then.

If the pressure went up to 3 bars with the heating on, but with a cold pressure of 1 bar, what would that mean?

 

[John.g]

It would mean that the pre pressure is incorrectly set (too high) or the air has leaked out of the exp vessel or it is too small for your system.

 

[ought74]

Right. Being as the boiler was working I would guess the middle one would be the likely one.

I will run the heating later and see what the pressure goes up to when the PVR pipe drips.

Either way it does not sound like a system leak does it.

 

[John.g]

Doesn't look like a system leak.