New Boiler losing pressure but no sign of leak

[RHOBHfan]

We’ve recently had a new boiler fitted (end of May)

It’s losing pressure - we’ve had to top it up 3 times so far. (no idea if that’s normal but I’m guessing not)

We have no signs of a leak at all. None of our radiator pipe work runs underground so fairly sure we’d see one if we had one.

In addition, one of the radiators (and only one) doesn’t appear to work now. It’s been bled.

Anyone else had this? Our plumber has said if there’s no sign of a leak, his hands are bit tied (and I get that... I certainly don’t want him ripping up floors to investigate)

[BernadetteRostankowskiWolowitz]

Well I'd be getting the person who fitted the boiler back to do a proper investigation. Did they supply the boiler too? They fitted it less than a month ago. It should be in good working order.

I'd have no problem getting onto the phone and highlighting that the work they've done is not satisfactory.

[RHOBHfan]

I have no problem doing that either; but to do what though?

The obvious answer is, it’s a leak. How do they investigate that with no visible signs anywhere?

[BernadetteRostankowskiWolowitz]

Get him to inspect his fitting of the boiler. Make sure everything is exactly as it should be.

In the meantime; call the manufacturer and explain the issue and see if they can advise

[BernadetteRostankowskiWolowitz]

I think, also, that you have to bleed all your radiators, not just the one that isn't working

[Toddlerteaplease]

My parents had this issue. I think a rubber diaphragm had perished.

[gotothecooler]

I have no problem doing that either; but to do what though?

To find out the problem and fix it. Although I'm not sure why you brought in a different plumber when the boiler is so new, I would have gone right back to whoever installed it.

[sbplanet]

Or maybe the pressure release valve is faulty, or the expansion vessel?

[RHOBHfan]

@gotothecooler

I have no problem doing that either; but to do what though?

To find out the problem and fix it. Although I'm not sure why you brought in a different plumber when the boiler is so new, I would have gone right back to whoever installed it.

I didn’t bring in a different plumber.

I’m asking... if there’s no sign of a leak, how do you find one given this is the most likely reason for a boiler losing pressure?

[RHOBHfan]

@Toddlerteaplease

My parents had this issue. I think a rubber diaphragm had perished.

Interesting, thank you. Was it a new boiler?

[RHOBHfan]

@BernadetteRostankowskiWolowitz

I think, also, that you have to bleed all your radiators, not just the one that isn't working

Thanks - Have done that today and got a lot of air out of one... be interesting to see if that has any effect.

[Flamingolingo]

The plumber has to come back. If there is just one problem radiator though you can try to make it work by turning all the others off at the TRV, making sure the hot water is not on and forcing the heat up. We have one that always needs this doing after the system has been drained. It must get an airlock. We also have a heating system that needs to be topped up a couple of times when it’s refilled. It then usually settles. Is it a big house?

[gotothecooler]

I didn’t bring in a different plumber.

My mistake. You referred to 'your plumber' in the OP so I assumed he had been to look at it.

I’m asking... if there’s no sign of a leak, how do you find one given this is the most likely reason for a boiler losing pressure?

It doesn't really matter imo. It's not working properly so get the person back to sort it. It's not up to the customer to try and figure this out, it's up to the installation team.

[RHOBHfan]

@Flamingolingo

The plumber has to come back. If there is just one problem radiator though you can try to make it work by turning all the others off at the TRV, making sure the hot water is not on and forcing the heat up. We have one that always needs this doing after the system has been drained. It must get an airlock. We also have a heating system that needs to be topped up a couple of times when it’s refilled. It then usually settles. Is it a big house?

We’ve done that (turning off at TRV and turning heat on)

Interestingly though, not sure hot water was off at the time... I’ll recheck tomorrow. Thanks!

It’s a 4bed detached, so not huge, but not tiny.

[RHOBHfan]

@gotothecooler

I didn’t bring in a different plumber.

My mistake. You referred to 'your plumber' in the OP so I assumed he had been to look at it.

I’m asking... if there’s no sign of a leak, how do you find one given this is the most likely reason for a boiler losing pressure?

It doesn't really matter imo. It's not working properly so get the person back to sort it. It's not up to the customer to try and figure this out, it's up to the installation team.

Yes, by our plumber, I meant the one who installed the boiler.

I know what you mean about not thinking about how to fix it and leaving it up to them; but I’m not prepared to allow them to start ripping up floors alles uber der platz to find a leak that may or may not be there. I’m trying to understand whether there are other diagnostic options/other potential causes.

Anyway... we’ve gone back to him and asked him to come out to have a look... I’ll report back!

Thanks for all your advice/suggestions.

[Flamingolingo]

@RHOBHfan I’m all out of ideas then. I asked about size because our heating system is big (16 rads, some rooms have two rads) and I think the size of ours means there is more space for air to get trapped. So when it’s drained and filled it often needs a top up after a day or two.

[TwoKidsStillStanding]

We had this! Boiler had only been fitted 3 months and problem started around a month in (during lockdown). Plumber who fitted the boiler thought we had a leak. No sign of one anywhere.

He then decided it could be related to the heat exchanger or pressure expansion vessel. Recommended we get it repaired under warranty. Guy came round. Nothing wrong with boiler. Definitely a leak.

Plumber came round with colleague. 45 minutes in, they found the leak. It was in the kitchen and an old heater which we don’t use was connected to the hot water system and was leaking.

So we did have a leak. If there’s no sign of a leak round any radiators, it’s probably in the pipe work. If there are no brown marks on ceilings, it’s probably on the ground floor. Is any water leaking from the overflow pipe outside, or the condenser if it’s that kind of boiler? Do you really have no pipe work under the floorboards? What about under the bath, etc? Is there anything which may have been connected to the heating/hot water system which could have been disturbed by the power flush when the new boiler was put in?

I agree that your plumber needs to be leading the investigation, not you! Ours talked me through the more obvious checks as we were in lockdown but had to come out in the end.

[RHOBHfan]

Thought I’d update this in case it’s useful to anyone in future.

Plumber who fitted boiler came back 4 weeks ago and found a blockage which he removed.

Result = radiator now works and no pressure lost for 4 weeks. Presumably the blockage was causing pressure to be lost through a safety valve somewhere.

Anyway; it appears to be sorted, thankfully!