Help!! Rapid leak of heating system

[captain_pugwash]

Folks,
I'm urgently seeking advice to get my heating going. The boiler (Glow Worm 30si) now loses all pressure in about two hours and so cuts out until I re-fill. The PRV on these things has been an issue so was the first thing I checked and it's fine - no water coming out of the pipe (put a jam jar under it to make sure and it's empty). I've filled and re-filled five time in the last 24 hours to keep the house warm so this water must be going somewhere.
I guess it must be a leak in the pipework to/from the radiators - not upstairs as I would seen the water coming through by now. I checked every flow/return connection visible above the floor on the radiators but no leaks visible. I know that a full boiler is about a bucket full of water s0 somewhere must be five buckets of water and I guess this must be under the floor somewhere. I have tongue in groove floorboards so will be a MAJOR pain to try to lift there (skirting board will have to come off).

Any advice from anyone that has had a similar problem and managed to trace the leak????

Cheers

 

[oilman]

I can't solve your problem easily, but there are probably only 5 cups of water rather than 5 buckets that have leaked.

When was the boiler last serviced?

Has the expansion vessel been checked?

 

[Paul Barker]

When the heating was fitted they took up some boards, aswell as when the sparkies did their work, just take up those boards. If none were taken up then you are looking for three boards toghether like in the cupboard under stairs where they made large enough hole for man to fit through and crawl around udner whole house. You'll find something, they didn't do it by telepathy. Only time there is a real problem is the nitwits who have wooden floors or laminated fitted on top. All sensibilty gives way to the great god "home makeover".

 

[captain_pugwash]

Paul/oilman,
Thanks for the responses. Actually I have suspected the expansion vessel in the past because a few weeks back I noticed a significant rise in pressure when hot - much more so than it used to be. This is why I checked the PRV first. I got British Gas to check it out and it was holding 1 bar no problem. How could the vessel keep 'swallowing' the water from the boiler - if it's faulty would it simply not abosrb the pressure rise ? Be interested in your view of why the vessel could be the problem.

I'm glad you say it's 5 cups of water - I thought it would be the same amout of water that goes into the bucket when I drained the boiler to replace the PRV.

I've never used Fernox leak sealer - do you think this leak seems too fast for this to be effective ??

I've also read about services that inject gas into the system and detectors then used to pick up the gas emitting from the leak - to save trial and error pulling up floor boards. Any experience of this?

Cheers.

 

[oilman]

How did BG check the expansion vessel? They should have relased all the water pressure first and then checked the air pressure. Holding 1 bar on the water side is not enough. You could add a seperate expansion vessel anywhere on the system if the present one is awkward to change, and you can't have one that's too big.

Leak sealer is not needed until you know the expansion vessel is ok.

 

[captain_pugwash]

Oilman,
BG did indeed drain down the boiler, then put the pressure gauge on the valve to see what pressure it was holding - between 1 and 1.5 bar.

He then checked the small tube linking the vessel to the boiler to make it wasn't blocked.

There didn't seem much else he could suggest to test it. I e-mailed glow worm and they had no other suggestions.

My own limited view is that the water has to be getting out of the system as I think that even if the vessel was taking in water it would only hold a few re-fills of the boiler that I've been doing - it looks about half the size of a water bottle.

As such I think the water must be leaking out of a pipe somewhere under the floorboards.

Any other suggestions greatly appreciated,
Cheers

 

[keego]

I think it's time to grit your teeth & get the saw out, the only way you are going to find out if there is a leak under the floor is to get under it & inspect it. As Paul says pick somewere hidden to cut the boards, it's going to be quicker & easier in the long run.

 

[Agile]

Surprised no one else has suggested the obvious cause.

Most Glow Worm boilers have an auto air vent placed out of sight in the combustion chamber.

If your model has this then its most likely leaking the five cups of water which is enough to depressurise the system. The leaking water is harmlessly boiled away when the boiler is on and escapes attention.

The only problem is that opening the combustion chamber should only be done by a CORGI engineer so I cannot encourage you to do this yourself.

Tony Glazier

 

[captain_pugwash]

Folks,
Decided that the most likely place for a leak would be at each tail end of the radiators so connected 3 drinking straws together for length then taped a cotton bud to the end and routinely went around every radiator on the ground floor to (no stains on ceilings so confident not upstairs) and was about to give up when the very last try and the cotton bud came back wet. Called out Britsh Gas as I have pipe leak insurance with then and sure enough, one circular hole in the floor board revealed a leaking plastic elbow joint at the tail pipe of the radiator.
This is now replaced with copper fitting and system back up and running.

Learning point for me was that the water had to be going somewhere and was a case of finding a quick way to trace the damp without all the hassle of pulling up loads of floorboards. The straws and cotton bud worked well as we have a big drop between joists and bottom surface.

If this hadn't worked I would have been then tempted to use the system I saw on the Web of injecting gas into the system and then using a sniffer detector to find where the gas was coming up.

Anyway thanks to all for the suggestions and assistance,
Cheers

 

[scatmanjohn]

Agile Wrote:

Surprised no one else has suggested the obvious cause.

Most Glow Worm boilers have an auto air vent placed out of sight in the combustion chamber.

Probably because its "obvious" that its not that because the aav is sat on top of the pump on this boiler.

5 refills in 24hrs? I would be under the floor looking for a leak as suggested by the others.

 

[Agile]

Ok, its on top of the pump housing then! But has it been checked first before pulling up the floorboards?

Tony

 

[Paul Barker]

I assumed the amount of water talked about would have been noticed, and also assumed that because prv didn't discharge that EV was a red herring.

If there is that much space under joists there is certain to be a hatch somewhere, I would have found that rather than drill a hole in the floor.

 

[keego]

I'm with you on that one Paul, surely a hole somewere out of site has to be better than one right under a radiator.

 

[oilman]

How much space is nder the floor then? It would have to be loads to have a remote hatch and then climb down to go and change an elbow. Me? I'd drill a hole with a 4 or 5 inch cutter like what screwfix sell next to the pipe.

 

[Softus]

Surprised no one else has suggested the obvious cause.

Perhaps it isn't obvious?

The only problem is that opening the combustion chamber should only be done by a CORGI engineer so I cannot encourage you to do this yourself.

It's wise not to offer encouragement, but cp should be told the facts, which are that it is not illegal for him to carry the work on his boiler, in his own house, if he does not let the house, and does not carry out the work under the auspices of a business.