Combi boiler pressure loss - is any loss acceptable?

[Rockatansky]

The background information here is that this is a new build house, ideal logic combi boiler, and I've no previous experience of either of these things.....

I've noticed that the pressure on the boiler seems to be going down, albeit slowly. I topped it up a couple of weeks ago and made a note of the pressure on that date. It's dropped 0.2 bar in two weeks.

Is any drop over time acceptable?

The house is just within the two year snagging period, so I have a small window of opportunity to pass this back to them for investigation.

[saveloy]

Boilers will always lose some pressure over time; I top mine up every 3 to 6 months. It will go from 1.5 Bar to 1 bar in 6 months.

0.2 Bar in 2 weeks seems higher than normal. Did you fill it when cold & check the pressure from cold? Have you checked the radiators for any leaks?

Kyri

[Rockatansky]

saveloy said:

Boilers will always lose some pressure over time; I top mine up every 3 to 6 months. It will go from 1.5 Bar to 1 bar in 6 months.

0.2 Bar in 2 weeks seems higher than normal. Have you checked the radiators for any leaks?

Kyri

I have checked, and there's nothing obvious.

[Drumroll]

You have just reminded me to check mine 0.3 bar over 3 months.

[Little Lofty]

I haven't topped mine up since it was fitted over 18 months ago. Many do, but they shouldn’t really lose pressure on a regular basis.

[Aluminati]

Little Lofty said:

I haven't topped mine up since it was fitted over 18 months ago. Many do, but they shouldn t really lose pressure on a regular basis.

This.

[CharlesElliott]

Most installs will have some self bleeding valves in them somewhere - so if there is any air in the system it will work its way out and drop the pressure. But it should not lose any pressure if it is water tight and all the air is out.

[caziques]

CharlesElliott said:

Most installs will have some self bleeding valves in them somewhere - so if there is any air in the system it will work its way out and drop the pressure. But it should not lose any pressure if it is water tight and all the air is out.

and the expansion vessel is correctly set

[Sheepshanks]

Rockatansky said:

I have checked, and there's nothing obvious.

It’ll be a smallish, but not insignificant, amount of water - maybe half a litre, perhaps a bit less.

[leef44]

This happened to me with my Worcester Bosch. Within two years after installation it was losing 0.2 bar in a week. A pressure test did not reveal any leak so it was presumed to be the piping under the concrete floor.

I had the pipes re-routed above ground and the leak persisted. This was year 3 by now and it was leaking 0.2 bar a day. A pressure test now revealed it was the boiler.

Under warranty, the heat exchanger was replaced.

The leak in your boiler might be too small to reveal a hair line crack but in time it would get bigger and a pressure test would show it up. It would be the boiler manufacturer who would repair under warranty.

[scot_aln]

Over a period we had 2 different new build homes in the same small estate. Same heating system bar very slightly higher capacity. So it came as a surprise when the later home needed topping up ever other month. In hindsight not sure whether the pressure test was insufficient but it showed no issues. It was only about a year in and on removing some skirting we discovered it had multiple nails into the CH pipes. It'd been watertight but not airtight. When we had that 15cm of pipe replaced topping up was no longer a regular thing.

[Rockatansky]

Thanks for your replies.

I've a bit of time tomorrow, so I'll give everything that's accessible a good visual check then.

I have previously had to have the builder send a plumber out to fix a leaking zone valve, I thought that was fine but I'll uncover that and double check.

I don't really want any flooring ripped up, but if I can get that done while it's still their responsibility then that's a result.

[Sheepshanks]

Is there any way you can access the condensate drain? As another posted suggested, it certainly could be a crack in the heat exchanger. Usually leaks worse when the boiler is working so a bit difficult to try over an extended period at this time of year.

[Rough101]

My system dates to 1996, it’s on its 4th boiler, has been extended and altered all over the place, been topped up no more than once every 18 months.

Anything more than that in the past equalled a leak, sometimes inside the boiler, sometimes a weep at a valve, once the vessel.

Make sure it’s fully aired though, as that can look like a leak as the air compresses..

[Rockatansky]

Thanks again, I'll bleed the radiators as I go round inspecting them.

[saveloy]

Another thing to do is note the pressure when the boiler is inactive, then firing up the heating; the pressure jump should be about 0.5 bar.
If it's more then it's quite likely your expansion vessel has failed.

Kyri

[Rockatansky]

saveloy said:

Another thing to do is note the pressure when the boiler is inactive, then firing up the heating; the pressure jump should be about 0.5 bar.
If it's more then it's quite likely your expansion vessel has failed.

Kyri

Interesting, I'll try that.

[OutInTheShed]

Rockatansky said:

The background information here is that this is a new build house, ideal logic combi boiler, and I've no previous experience of either of these things.....

I've noticed that the pressure on the boiler seems to be going down, albeit slowly. I topped it up a couple of weeks ago and made a note of the pressure on that date. It's dropped 0.2 bar in two weeks.

Is any drop over time acceptable?

The house is just within the two year snagging period, so I have a small window of opportunity to pass this back to them for investigation.

Have you lived there for two years and this is a new thing happening?
Or you've moved in recently?
Has the boiler been serviced? When?

Boilers can lose pressure for numerous reasons.
Tiny leaks around rad valve spindles are common.
It can take a while to get all the air out after servicing.
Your boiler probably has an auto-bleed valve, so will dump air automatically when it reaches the boiler.

My system goes from 1.8 to 1.5 over a few months. It varies a bit with temperature too. Being a combi boiler, it's rarely completely cold.

[Rockatansky]

OutInTheShed said:

Have you lived there for two years and this is a new thing happening?
Or you've moved in recently?
Has the boiler been serviced? When?

Boilers can lose pressure for numerous reasons.
Tiny leaks around rad valve spindles are common.
It can take a while to get all the air out after servicing.
Your boiler probably has an auto-bleed valve, so will dump air automatically when it reaches the boiler.

My system goes from 1.8 to 1.5 over a few months. It varies a bit with temperature too. Being a combi boiler, it's rarely completely cold.

Yes, we've been here since day one. Whether it's a new thing or not in not I'm not entirely sure.
It did lose enough pressure to stop working more than a year ago after we were away on holiday, I never really investigated that. I've been paying more attention since the valve leaked a few months back and damaged a ceiling.
It has been serviced, just under a year ago, probably due again soon.

[Sheepshanks]

OutInTheShed said:

My system goes from 1.8 to 1.5 over a few months. It varies a bit with temperature too. Being a combi boiler, it's rarely completely cold.

Is that 1.8 when cold? It seems a bit high - is there a reason for that?

Ours sits at 1.1 when cold. Half our system is quite old and I wanted to keep it as low as reasonable - apparantly it'd fine down to 0.5.