Boiler losing pressure

[Rupster]

After a recent annual service, my boiler pressure seems to dropping around 0.1 bars each day.

Before I call the engineer back to have a look, any ideas what might be causing it?

Possibly a leak somewhere - see if you can find a water leak.

We had this issue - one of the valves on the pipes wasn't tight enough.

I've checked all the radiators, but no sign of any leaks.

If the pressure is dropping it’s usually a leak somewhere , it could be inside the boiler and the heat inside is drying it out before you can notice it ?

It is more likely that the pressure vessel has either failed or doesn't have enough pressure in it. Some are inside the boiler or you will see a large vessel by the boiler. Ours very occasionally has to be re-pressurised (can do it with a normal pump). If there isn't enough pressure it spits out water outside.

We have had this a few times over the years and is easily sorted

We had this for ages while trying to keep our old boiler going. Would wake up freezing and no hot water and manually topping up.

In the end some pressure valve thing had gone. They fixed it and kept it going for another year before it finally died.

We had this and there was a tiny leak in the boiler, we couldn’t see it but gas engineer found it and replaced a part

Did the engineer bleed your radiators? If so, I’d just check they were adequately tightened afterwards.

We had this 2 years ago.( WB boiler 8 years old) We were told we needed a spare part or maybe even to replace it!
Here we are today and there are no probs.
I think possibly ours had been turned up to maximum and it does
not like that.

We had the same thing for years. Under our combi boiler are two taps, we had to turn one tap all the way on (which didn't do anything) and then turn the right hand tap on until we saw the pressure gage go up to "11 0'clock" ok the dial. Then quickly turn the right hand tap back off and turn the left one back off after. Took several call outs before a helpful plumber showed us how to do it ourselves

As a pp said, bleed your radiators. Also, do you have a bottle shaped part below the boiler for the water to pass through to be cleaned? Sometimes the brand is magnaclean. The tiniest crack in that (it's plastic) can cause pressure loss.

I've had a closer look inside the boiler, but can't see any leaks.

There's no Magnaclean on the boiler.

Just one rad valve was turned to let some air out, but that's not leaking.

I rang the engineer, and he suggested letting the pressure drop to 0.2 bars before topping it up, and then only going to 0.8 bars (as it's an old boiler). He says there's little he can do without any sign of a leak, without spending several hours potentially lifting up floorboards, etc.

I guess he would have re-pressurised the pressure vessel as part of the service.

I think he's hoping the leak will fix itself once the pressure has remained lower for several days.

The pressure seems to be falling a little slower now, but time will tell I guess.

Thanks for all your replies.

There is an additive that can fix small leaks like this.

My plumber advised against using an additive to seal leaks as he said it wouldn't be good for the boiler.

My plumber advised against using an additive to seal leaks as he said it wouldn't be good for the boiler.

First time I've heard that

The pressure seems to have stabilised at just under 0.5 bars now.

I've now noticed a couple of radiators are slowly filling with air, so the system must still be losing water and letting air in somehow.

A plumber's coming to have a look at it on Monday.

OK, so the plumber had a look but couldn't see any leaks anywhere, so he added some leak sealer to the system, and this has stopped the pressure dropping.

That was 3 weeks ago, and the pressure's still OK.