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

[ought74]

Hello,

Can anybody please advise.

For months now our old Ideal Mini HE C24 (combi boiler) has had pressure problems. It won't stay above 1 bar. Occasionally I top it up, to above one bar, twice in a day, other times if I am happy to leave it about a 1/3 of a bar it won't complain for a week. Usually I would probably top it up a couple of times a week, on average.

We live in a house with concrete foundations and all the pipework is above ground or on the 1st floor below the floor boards. There is no sign of a leak anywhere. No damp patches on the ceilings, no raised flooring, nothing that would indicate a leak. Of course some of the pipework is boxed in but there are no signs at the bottoms of the boxing. Some piping is behind kitchen cupboards but the floor underneath is dry.

If I top up the pressure to above 1 bar there will sometimes be a slow slow gentle drip from the PRV outside, but never a gush. If the pressure is low then nothing comes out.

The pressure goes up to near 2 bars when the heating is on.

So as I can not see any sign of a leak in the house I have assumed it is the boiler being wrong somewhere. I have had a couple of people in and they don't seem to agree. I am told if there was a problem with the boiler water would be squirting out of the PRV. I just don't see how I can have a leak in the house, for such a long time, with no signs at all.

Might anybody have any ideas or suggestions please?

Is there any way to easily check if it is the boiler or the system? I have read something about isolating the boiler but I am not really sure.

Also in the last few weeks the boiler has become more unhappy and sometimes won't fire for hot water, though it always works for heating.

We do need a new boiler but unless the leak is sourced it seems that is not a good idea.

Thank you.

 

[John.g]

I would renew that PRV pronto, it doesn't take long to lose your exp. vessel reserve of 1 to 2 litres

 

[cjg]

change prv first, then run boiler, check prv again when boiler has run for some time on heating, watch presure, if up to more than 2bar re check prv, if dripping , presure gauge faulty, change that. then check expansion vess.

 

[SJB060685]

A PRV will never gush water unless it seizes wide open. Under normal operation the pressure in the system rises to spring tension pressure, the valve opens and sea saws between open and closed providing a constant drip.
From your description I suspect either a faulty PRV or a bit of grit stopping it from seating properly. If the pressure on the gauge at the boiler is less than 2.5-3 bar (depends on the PRV setting) when the PRV lifts then I would arguably change the valve first.

 

[Limecc]

For micro leaks Worcester Bosch themselves recommend a leak sealer. I don't know about Ideal but you could try that if a new PRV doesn't fix it.

 

[John.g]

Suggest addressing the PRV issue first.

 

[ought74]

Thanks for the replies.

Is the PVR something I could change myself?

To explain the situation, we are a low income family with two young children, so the energy company will install us a boiler for free. The expert came to size us up for a boiler based on rooms, radiators etc. He asked what the problem with the boiler was. I said it is 18 years old, doesn't always fire up and drops pressure.

He said they are not allowed to approve installations where there is a pressure drop as then the company would be liable for any system leaks in future.

I explained that I did not see how there could be a leak in the system (for the reasons mentioned above). He said that as there was no water even dripping out of the PVR at that time, or sign of water it could not be the boiler. That we must have a hidden lean somewhere. I told him I'd not topped it up for a few days but when I do the PVR drips. He said that if a PVR went it would be spaying out.

He said we had a choice of paying them £3700 to replace all the pipes in our 2 bed house or we could fix the leak ourselves by doing a test and trace or maybe get somebody to use a sealant. Then get the new boiler for free.

£3700 is mad and I really do not believe there is a leak in the system so it seems we are in the situation where if I am right, we need to fix our 18 year old boiler, so then we can get a new one fitted. It seems crazy, money is tight and they are supposed to help us.

So if I can replace the PVR myself, and then the pressure stays up, they will then replace the blimming thing!

What do you think?

 

[John.g]

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.

 

[Limecc]

Thanks for the replies.

Is the PVR something I could change myself?

To explain the situation, we are a low income family with two young children, so the energy company will install us a boiler for free. The expert came to size us up for a boiler based on rooms, radiators etc. He asked what the problem with the boiler was. I said it is 18 years old, doesn't always fire up and drops pressure.

He said they are not allowed to approve installations where there is a pressure drop as then the company would be liable for any system leaks in future.

I explained that I did not see how there could be a leak in the system (for the reasons mentioned above). He said that as there was no water even dripping out of the PVR at that time, or sign of water it could not be the boiler. That we must have a hidden lean somewhere. I told him I'd not topped it up for a few days but when I do the PVR drips. He said that if a PVR went it would be spaying out.

He said we had a choice of paying them £3700 to replace all the pipes in our 2 bed house or we could fix the leak ourselves by doing a test and trace or maybe get somebody to use a sealant. Then get the new boiler for free.

£3700 is mad and I really do not believe there is a leak in the system so it seems we are in the situation where if I am right, we need to fix our 18 year old boiler, so then we can get a new one fitted. It seems crazy, money is tight and they are supposed to help us.

So if I can replace the PVR myself, and then the pressure stays up, they will then replace the blimming thing!

What do you think?

I think you've been fobbed off. Try again and don't mention you have any leaks. It's temperamental and you want a new efficient model. Reality is it's a boiler fault the system isn't leaking. Change provider if no joy.

You can try the sealant as an easy first option but it's probably the relief valve that's the cause. The sealant would confirm.

Shame you don't have a trustworthy plumber as a friend.

 

[cjg]

It's not technically illegal to carry out DIY gas work in your own home* as long as you are 'competent' to do so, but the consequences of doing so without the necessary skills are hugely dangerous. Working with gas is a complex and dangerous task that requires extensive training, knowledge and experience. your prv is not gas related... but i do stress that if its gas or burner LEAVE IT ALONE,!!!!!!!! and get a gsr engineer in . BECAUSE you think you have done it ,THEN BOOOOOOM.

 

[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.

 

[ought74]

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]

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]

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.

 

[cjg]

sounds very much like expansion vessel,