Hi,

First post on here; will be looking through other posts too to see if there is anything similar to my problem.

We have a 6 year old Glow Worm combi boiler. Unsure of the model number at this time. The pressure happily sat around 1.1 bar, dropping occasionally over time, but nothing serious. We had the boiler serviced about a month ago and since then the pressure has been creeping up. After about a week or two it was up to 1.5 bar. It has since steadied about 1.7 bar. Yesterday we had the heating on and I thought about increasing the radiator water temperature. I went to have a look at noticed that there was water dripping from the outside pipe and that the boiler pressure was at 4.1 bar. I turned the heating off and it reduced to 1.7 bar again. I popped the heating on again this morning just to see what happened and it wasn't long before it was up at 3.5 bar.

I need to call the boiler chap, but could anyone possibly hazard a guess at what could be causing this? Thank you.

Expansion vessel gone flat

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Dave

www.drlgas.co.uk

Yup job for the installer, might work if re-pressurised but may need a new vessel.
Unlikely to be a result of the service as the only thing that might have caused it is if some twerp has bled the valve on the vessel, but that would have started straight away afterwards.
Sounds like just bad luck in this case

+ 1

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The pressure creeping up could be a couple of things, filler loop letting by (worth disconnecting if poss) or a pinholed heat exchanger.

It may well be that you have one issue causing the pressure to creep up whilst off and another causing the overpressure whilst running.

Best to get the guy that serviced it back...

EDIT bleed some water from a rad using a bleed key to get the pressure down to about 1.1 bar cold; fire up the heating. What does the pressure gauge rise to ??

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Verwood Handyman

Verwood Handyman


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Hi, thank you for the replies.

The problem with the pressure rising was immediately after the boiler had been serviced, but gradually appeared to slow down.

I bled the system down to 0.9 bar. I let a bit too much out to be honest but figured it's still in the ok-when-cold region. I put the heating on and it increased to 1.8, then crept up to 2.0 and stayed at 2.0 whilst the heating was on. One thing worth mentioning at this stage though is that 1 of the main radiators wasn't on last night because we'd just had some wallpapering done and were told to let it dry out naturally.

I checked the pressure again this morning and it was back down to 0.9, but today I'll fire up the system with the large radiator on again and see if it makes any difference.

It may be worth mentioning, I noticed the setting on the boiler for the radiator temperature was set on max (82 degrees) and I lowered it down to 75. Would this likely make any difference to the rate the pressure bar raises?

So I turned the larger radiator back on yesterday, and upped the boiler radiator temperature to 80. After a couple of hours the pressure bar on the boiler had reached 2.5/2.6.

This morning the pressure on the boiler was sitting at 1.2; I'm not sure if that would be down to the fact there was still pressure in the system due to having the heating on, or if the pressure is just starting to creep up again.

Dave (gas for you) will be able to advise further, but as the base pressure (cold pressure) increases after running the heating I would suspect a pinholed heat exchanger...

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Verwood Handyman

Verwood Handyman


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If the plate was pin holed I would expect the pressure to increase all the time, regardless of whether the heating is on, as it would if the filling loop was letting by.

I still think the expansion vessel pressure needs checking, or the expansion vessel itself before anything else is considered.

If I ever go to a service where the customer says they are having to keep topping up the boiler, or the pressure rises too high I would always do this as a matter of course.

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Dave

www.drlgas.co.uk

Thanks again. I have our boiler engineer coming out on Tuesday morning. I explained the problem to him and his initial reply was also that it could either be the filling valves or the expansion vessel. Will update as he comes out.