Radiators too hot and system constantly losing pressure

[sbloxxy]

Hi everyone. Yet another problem with my central heating boiler: its a Sabre 35HE. This time its losing pressure very quickly - will lose everything within 2/3 hours. I've done the obvious and checked for leaks. Unfortunately ours is a large and slighty rambling house so while its hard to be certain, I don't think I have any leaks anywhere. I even had floorboards up and still no sign of anything untoward.

It started doing this perhaps 10 days ago and I had to re-pressurise 2/3 times a day. Then all of a sudden it just worked perfectly for 3 or 4 days with no pressure drop. But now the problem has returned. Another symptom that worries me is that the radiators are absolutely red hot, though I'm guessing that may be connected to the low pressure? I'm also getting lots of gurgling noises from the radiators.

I've checked the expansion vessel: pressure is about 10lb/ft (using a tyre pressure gauge) and there is no sign of excess water in the vessel. Also no signs of the PRV leaking.

Has anyone got any ideas of what to check next? Any ideas gratefully received.

 

[Gas2Air]

Hi everyone. Yet another problem with my central heating boiler: its a Sabre 35HE. This time its losing pressure very quickly - will lose everything within 2/3 hours. I've done the obvious and checked for leaks. Unfortunately ours is a large and slighty rambling house so while its hard to be certain, I don't think I have any leaks anywhere. I even had floorboards up and still no sign of anything untoward.

It started doing this perhaps 10 days ago and I had to re-pressurise 2/3 times a day. Then all of a sudden it just worked perfectly for 3 or 4 days with no pressure drop. But now the problem has returned. Another symptom that worries me is that the radiators are absolutely red hot, though I'm guessing that may be connected to the low pressure? I'm also getting lots of gurgling noises from the radiators.

I've checked the expansion vessel: pressure is about 10lb/ft (using a tyre pressure gauge) and there is no sign of excess water in the vessel. Also no signs of the PRV leaking.

Has anyone got any ideas of what to check next? Any ideas gratefully received.

Sabre HE Did you check EV when cold and no pressure pushing back on it? IE an open end? Put a balloon on PRV, just to make sure, it does sound like a major leak on the system. Close flow and return to boiler and check in morning. Does the pipework downstairs go under concrete at all?

 

[sbloxxy]

Thanks for that. Checked the EV this morning when cold and it still seems ok with air coming out of valve rather than water. Also fitted a small bag over the PRV exit and thats ok too. Am I right in thinking that this MUST be a leak somewhere.

 

[Gas2Air]

Thanks for that. Checked the EV this morning when cold and it still seems ok with air coming out of valve rather than water. Also fitted a small bag over the PRV exit and thats ok too. Am I right in thinking that this MUST be a leak somewhere.

Fill to 2 bar. Leave system off for the next 2 hours. Re-check every joint you can and then post how much is lost.

 

[sbloxxy]

Ok, filled to 2 bar and within 2 hours it had lost 1.8 bar. Heating system has been off over this period. Seems like a lot.

 

[Gas2Air]

Ok, filled to 2 bar and within 2 hours it had lost 1.8 bar. Heating system has been off over this period. Seems like a lot.

Where do your downstairs rad pipework go? That's a leak, a big one. If you can't find it, it will mean re-pipe.

 

[sbloxxy]

Joy at last. Found a big leak. Thanks to user 'Gas2Air', I decided to check everywhere again for leaks and discovered some damage in the one place I hadn't looked. It was where the pipework disappeared into a wall behind some shelves in our utility room. It looks as though a mouse has been chewing the plastic pipe and a fine spray of water was escaping. Damage section replaced and - though its early days - I can see an immediate improvement in pressure.
Thanks again, Gas2Air for your help - much appreciated.
Steve