Boiler pressure dropping - where's the water going?

spongerobinson

Hi all,

So the pressure on my boiler is dropping regularly. Topped it up to 1 bar a few hours ago, and it's now down to half a bar already after having the heating on for an hour. No sign of water from the PRV outside, and no sign of a leak anywhere inside.

Firstly, am I topping it up correctly and right in thinking that it doesn't matter if the valves are all open or not at the time?

Secondly, how much water would have to be lost for the pressure to drop from 1 bar to 0.5 bar?

When we first moved into the house there was water dripping from both towel rails, but had a plumber replace both valves and since then I haven't seen any drips anywhere.

Would leak sealer be likely to help in this situation?

I need to get the boiler serviced soon so will ask the guy his opinion, but thought there might be some good opinions from the experts on here too.

Thanks in advance for any advice!

scamalert

had completely opposite issue few months back, someone with expertise came around and sort of figured what caused mine boiler to start leaking as it would easily hit 3bar and release valve would start dripping, what was interesting that somehow it has a feed to the mains and whatever runs out it tops back up.


Not an expert at all but a bump, before someone knows boilers comes to help.

spongerobinson

Thanks @scamalert. I've a guy coming to service the boiler in the next week, so hopefully he might be able to shed some light on it or provide a fix.

John.G

spongerobinson wrote: »

Hi all,

So the pressure on my boiler is dropping regularly. Topped it up to 1 bar a few hours ago, and it's now down to half a bar already after having the heating on for an hour. No sign of water from the PRV outside, and no sign of a leak anywhere inside.

Firstly, am I topping it up correctly and right in thinking that it doesn't matter if the valves are all open or not at the time?

Secondly, how much water would have to be lost for the pressure to drop from 1 bar to 0.5 bar?

When we first moved into the house there was water dripping from both towel rails, but had a plumber replace both valves and since then I haven't seen any drips anywhere.

Would leak sealer be likely to help in this situation?

I need to get the boiler serviced soon so will ask the guy his opinion, but thought there might be some good opinions from the experts on here too.

Thanks in advance for any advice!

Before you jump to any conclusions, just press the schrader valve at the back of the expansion vessel with your thumb nail and see if air or water or no pressure whatsoever is present. It should have air pressure present.

If everything is normal and you have a genuine leak then you are possibly losing 0.5 to 1.0 lire/hour.

spongerobinson

John.G wrote: »

Before you jump to any conclusions, just press the schrader valve at the back of the expansion vessel with your thumb nail and see if air or water or no pressure whatsoever is present. It should have air pressure present.

If everything is normal and you have a genuine leak then you are possibly losing 0.5 to 1.0 lire/hour.

Thanks for the reply John. There is no expansion vessel in my system.

John.G

spongerobinson wrote: »

Thanks for the reply John. There is no expansion vessel in my system.

Well if there isn't then you have a very strange system, its no wonder you are topping it up so often!!

spongerobinson

John.G wrote: »

Well if there isn't then you have a very strange system, its no wonder you are topping it up so often!!

Thanks for the helpful reply John. If there is one, it's hidden somewhere. Definitely don't have one of the gas cylinder looking things in hot press.

Dardania

spongerobinson wrote: »

Thanks for the helpful reply John. If there is one, it's hidden somewhere. Definitely don't have one of the gas cylinder looking things in hot press.

Often times modern gas boilers have them internally. They can be small in comparison to system needs

John.G

Dardania wrote: »

Often times modern gas boilers have them internally. They can be small in comparison to system needs

Of course, (apologies) should have thought of that.

spongerobinson

Hi all, just to come back to this one, I had the boiler serviced and there are no problems with the boiler itself. The guy suggested it could be the expansion vessel as when my heating is on the pressure is rising from approx 1 bar (cold) to 2.5-3 bar (hot). I put a sandwich bag over the PRV valve outside and sure enough after having the heating on in the whole house this evening, I was left with a bag full of water. Strange as when I put my finger into the pipe it was bone dry, which is why I never thought it could have been this before.

So, just to reiterate before I call a plumber (the boiler service guy only does that) - how much approximately should pressure be rising by when heating is up to full temperature?

Thanks again

John.G

IF the gas boiler has a integral E.vessel then a plumber cannot check it, it should have been the service guy who I presume is qualified to work on gas boilers.
Of course the boiler may have been installed a good few years ago and does not have that integral E.vessel, if not then where is it I wonder.

What make/model of boiler do you have and is it gas or oil fired?.

The normal pressure rise between hot and cold should be ~ 1.0 bar.

spongerobinson

Hi John.

It's a Biasi boiler - not sure of the exact model. It's gas and yes the guy is RGI.

Considering my pressure rise is approx 1.5 bar with just downstairs heating on, and approx 2 bar with the whole house on I'm guessing that's the issue so!

agusta

spongerobinson wrote: »

Hi John.

It's a Biasi boiler - not sure of the exact model. It's gas and yes the guy is RGI.

Considering my pressure rise is approx 1.5 bar with just downstairs heating on, and approx 2 bar with the whole house on I'm guessing that's the issue so!

Where is the expansion vessel located...,Was it checked for pressure during the service...,Post 10 says its rising to 2.5 to 3bar.,

spongerobinson

I don't really know the answers to these questions, hence why I'm on here asking for advice. There is no expansion vessel in the hot press so I'm assuming it's built into or behind the boiler. I'll give another plumber/RGI a shout and see where I get from there. Thanks lads.

spongerobinson

agusta wrote: »

Where is the expansion vessel located...,Was it checked for pressure during the service...,Post 10 says its rising to 2.5 to 3bar.,

Yes it's rising from approx 1 up to 2.5/3.

John.G

spongerobinson wrote: »

Yes it's rising from approx 1 up to 2.5/3.

If you told the RGI this then it seems strange that he didn't tell you that there is no integral E.vessel although it is very likely that there is.