[Closed] CH boiler loosing pressure.

Is the expansion vessel heavy/full?

You could try something like Sentinel leak sealer?

When it is running where is the needle on the prressure guage? If it is out of the green and round near the red then you need to repressurise the expansion vessel.

If pressure is normal then chuck some leak sealer in to the system, the cheap one from Screwfix works well.

Thanks for the replies, much appreciated!

I’ve not paid any real attention to where the gauge sits when the heating is on but did notice it was around 1.5 bar when I had the heating on the other day. I usually have the pressure around 0.8 bar when the system is cold.

It did cross my mind to use some kind of leak sealant but was worried about causing more issues by potentially gumming the system up?

@Yak I can’t say if the pressure vessel is heavy or not as it is still in place. Is it worth depressing the valve to see if water comes out? I presume I’d have to relieve the CH system of any pressure before I tried to repressure the expansion vessel?

Is it worth depressing the valve to see if water comes out?

It's worth checking the pressure, certainly, but I would expect you'd notice more of a swing in pressure as the system heats up if it had failed.

How much pressure are you losing, and is it just producing an error code and not firing? Mine is different, but running it at .8 would be close to the point where even a slight dip/loss could trigger the error.

Should the pressure on the vessel be checked whilst the system is pressurised, or does the system need draining first?

According the the manual the pressure should be 0.75 bar.

First time round it lost all of its pressure and threw up the F1 error code so I topped it back up. It seems to loose about 0.1 bar a day I’d guess.

I’ve started to keep a closer eye on the pressure so see how it goes and I’ll bump it up to 1 bar cold. Thanks again.

Should the pressure on the vessel be checked whilst the system is pressurised, or does the system need draining first?

The boiler needs to be drained, not the entire system.

Are you checking whether you have a drip from the external end of the prv pipe, or directly underneath it (from the prv itself inside the boiler)?

Yes, I have a jar under the PRV outlet (the copper pipe outside?) and it’s bone dry.

To drain the boiler, is it a case of leaving the CH inlet and outlet closed then draining it? I can make out the hosetail to drain the boiler from on the diagram but can’t see the tap (I’m at work at the moment).

Don't mess about too much with the expansion vessel, can be a bit of a ball-ache to sort out if things go wrong. Easier would be to find the short copper pipe poking out of the external wall behind the boiler - it should loop back on itself and be pointing at the wall. Tie a plastic bag over the end and then let your boiler do its thing for a day or so. Check the bag and if there's water in it then your system is over-pressurising when heated and your expansion vessel is knackered.

Ah, just read the pressure relief pipe is dry.
I'd be looking at all the bleed valves on your radiators then seeing as you noticed the issue once you'd started doing that.

Yes the PRV is dry, as are all the bleed valves/TRVs etc. I’ve also checked all exposed pipe work through the house and looked everywhere for signs of damp but found nothing.

As it stands the CH system is isolated and the boiler is turned off. I’m not loosing pressure and there are no leaks anywhere rads/pipe work/valves/boiler etc that I can see. I did have a drip on the DHW outlet which I nipped up but would have thought that wouldn’t be anything to do with loosing pressure?

Yes, I have a jar under the PRV outlet (the copper pipe outside?) and it’s bone dry.

The PRV itself may be dry, but obviously any liquid it drips will evaporate very quickly inside a working boiler. Have a look for any condensate crust around the pressure/adjustment screw on top of the air vent.

Reading around the heat exchangers can be problematic on the Ideal Logics

Yup, just had the heat exchanger swapped on a 8 year old 35. The leak was hard to detect and we ended up having to get a detection company out. The leak rate seemed to vary depending on conditions that I couldn’t quite get my head around

So, I have drips on both the DHW inlet and outlet elbows and a green crusty mess on the inside bottom of the boiler.

Pressure has dropped from 0.8 bar to 0.7 bar in 6 hours with the CH system isolated from the boiler.

I’ve got a rubber glove tie wrapped to the PRV pipe with no signs of moisture. It’s looking to me like I potentially have a leak somewhere in the boiler itself?

Spotting the drip is half the battle, I suppose. Is the crusty stuff underneath the elbows? You could try tightening them slightly, or just call a heating engineer at this point.

Does sound like the bladder in the pressure vessel has failed, especially as this happened after you bled the radiators (air in the system would have worked in a similar way to the expansion vessel).

It's a real common problem.

However if it's still losing pressure with everything off and isolated then it's got to be a slow leak on the boiler but i would have expected it to be fairly obvious.

Same boiler, had the same pressure problem. Turned out to be a leaky pipework elbow buried in a wall. Before finding said leak we had the boiler serviced and examined twice.

Also, who services it makes all the difference. Some plumbers are way better than others.

Thanks again!

I am trying to get someone to look at it but the two usual plumbing/heating companies I used are booked up for over a week now. I’m trying to narrow it down before they get here and spend another few weeks sorting it.

Sorry to hear that muddyground, that’s what I’m dreading, a leak into somewhere out of the way ie a cavity or similar.

The CH side of the boiler is still isolated and the pressure had dropped slightly again. I turned the boiler back on and it immediately dropped ever so slightly again.

Does the pressure gauge read the pressure on the boiler side of the system or the CH side of the isolation valve?

Ha, it was annoying but having had a million boiler issues over the years, a leaky pipe was a relief! Boilers are the devil's spawn.

Hi there. I had a loss of pressure in my system. It turned out to be field mice that had gnawed the plastic pipe unser the suspended floor in my living room. Evidently they like to do this to keep their gnashers sharp. Resolved by replacing pipe with metal shielded pipe. Problem solved.

We’ve had mice previously but no sign of them for years (hopefully)!

The bulk of the rot seems to be under and around the heat exchanger. It doesn’t look the best if I’m honest.

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Also have damp underneath the main housing;

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Thing is that heat exchanger is for the hot water specifically. It could well be coincidence and it's only just happened but I think you'd have noticed the leak before now if the plate heat exchanger was burst. I guess one way to check would be to run the hot tap for a long while and see if the pressure drops.
The other problem is that water finds the low point regardless of where it's leaking from, so I wouldn't put too much stock in the location of the gunk.
If it's started leaking since you fired up the central heating it's 99% got something to do with that. I'd maybe check diverter valve and flow/return manifold connections.

Having said all that, technically you shouldn't be playing about inside the case of your boiler at all unless you're GasSafe registered. The front case forms a gas-tight seal and should only be removed by "a competent person".

Thanks again, panic ye not. Ideal are coming out to it on Monday so hopefully we will have an answer then.

Anybody local (who is half decent) are booked solid.

If you call the gas emergency number then they will be able to check for obvious leaks, and check the mains pressure is correct (at the ECV at least). Dont suppose you know if any neighbours have had any issues as well?

Thanks j4mie, it wasn’t an issue with gas pressure but the water pressure.

Slightly embarrassing, but had another good look for a leak over the weekend and discovered the radiator in my lads room had been leaking quite badly from one of the valves, running down the skirting board and onto his carpet which was soaking wet. I’ve nipped the nut up on the pipe which seems to have stopped it for now but will replace it when I get chance.

Just a very slight loss in pressure over the past couple of days, I’m hoping it’s one of the auto vents I fitted onto a couple of the rads last year letting the last of the air out of the system but will see how it goes. Got a service booked for Friday and I’m tempted to add some of the Sentinel sealant suggested earlier as it seems to get good reviews although I imagine I may have to ditch the auto vent valves if I do.

Perhaps it's trying to tell you something:

https://www.theguardian.com/world/2021/sep/29/wednesday-briefing-gas-boilers

My mum had this.

Plumber was at wits end with it.

Last resort was to swap every thermostatic rqdiator valve in the house. When they get old they weep very slightly from around the pin as the head moves it.

That fixed it.

If yours are 20 years old + , might be worth doing.

Perhaps it’s trying to tell you something:

https://www.theguardian.com/world/2021/sep/29/wednesday-briefing-gas-boilers/blockquote >

Ironic really that we are being told there's no generation issue in the UK and yet we electrics Gone through the roof due to generation issues.... Gonna be fun when we all have heatpumps going 24/7 flat out keeping our housing stock tepid.

But either way replacing the boilers not gonna fix a leaky pipe so not really relevent here.