Help Glow worm 38cxl losing pressure.

[jono73]

My combi loses pressure when heating is off, normally overnight.
Can't see any leaks from any rads, the highest rad (towel rail rad in bathroom) is full and hot when heating is on.
Overflow / blow off pipe outside is dry.
No visible leaks around the wall mounted combi.
before I rip up the floor in search of underfloor pipe leaks anyone got any ideas pleeeaaassee!!!

 

[MrV]

You can try closing the isolation valves on the heating flow and return from the boiler over night to see if it still loses pressure. If it does then it's the boiler. If it only loses pressure when you re-open the valves, it's the system.
Remember to ensure the boiler isn't going to try and fire up though.

 

[jono73]

Thanks any idea as to which ones they are?

 

[MrV]

To be honest buddy, if you're not sure which pipes they are, maybe you should get your heating engineer to take a look at it. He'll know exactly what to do.

 

[jono73]

Fair comment, plumbers just aren't around when you need them . Do you mean the flo and return to the rads, I have located them?

 

[Agile]

Fair comment, plumbers just aren't around when you need them

Nonsense! Plumbers will come round whenever you pay them!

 

[jono73]

Well phoned 3 today offering extortionate payment, not one has got back to me, life must be good for plumbers hence I'm attempting a DIY fix

 

[Agile]

How much do you consider an extortionate amount for a Saturday?

I dont EVER remember anyone leaving a message offering an amount of money if I come round to them.

Many do seem to expect me to come round and diagnose their problem free of charge so that they can repair it themselves.

But I always charge for visits unless there are other benefits.

 

[jono73]

The extortionate bit was a joke
I wouldn't expect any tradesman to come out and not receive remuneration, certainly at the weekend, and if I've taken the trouble to get one out then I would happily let them do the repair.

In the meantime my combi is still losing pressure

 

[dunbar]

If you want to try what MrV has suggested then the pipes can be identified as follows.
Start at the pipe in the middle. Should have a yellow lever on it. That's the gas.
Two pipes to the right. That's the CH return.
Two pipes to the left of gas. That's the CH flow.
Top it up to around 1 bar then you can isloate using the valves on CH flow and return.
The problem with this is that the isolation valves may start to weep if they are of poor quality.

Best of luck.

 

[jono73]

Ok, topped it up to 2.2bar, shut off flow and return, went out for a few hours, on return it was 1.1bar, and there was some evidence of dripping from the blow off pipe outside .

 

[dunbar]

Assuming the boiler wasn't on when you went out it could be a couple of things.
If there is evidence of water in the warning pipe I would probably be taking a close look at the pressure relief valve as this could be letting by.
If someone in the past has used this valve for draining the boiler or the seal is damaged or perished then water will escape from your system.
Trace the warning pipe back to the boiler and you will see a brass valve with a plastic top, usually red in colour, with may be the words 3 Bar on it.
If you're feeling confident there's normally a compression joint where the warning pipe joins this valve. Try undoing it and see if it's dripping.
Please bear in mind that this is considered a safety device so don't attempt it if you are unsure what I'm getting at.
Remember the more pressure you put in the faster the leak so be ready with a container or something.

 

[Whitespirit66]

Sounds like you have a problem with your expansion vessel, pressure release valve, or both.

You could check the FAQs for info on Exp vessel pressure, or get an engineer in.