Gloworm cxi30 boiler losing pressure (v slowly)

[H2O1969]

I have a Gloworm 30cxi boiler which was fitted 2 years ago with a brand new central heating system. It is located downstairs.

I noticed that it was losing pressure (Sept 2009) and found a leak under the boiler. The central heat pipe returning to the boiler was leaking and has been tightened and fixed. Then a downstairs towel rail started leaking; that was tightened and fixed. And finally the other central heating pipe leaving the boiler started to leak - that has now been fixed too.

BUT, it is still losing approx 0.1 bar/week. I've looked everyone for signs of a leak but can't find any at all. I'd rather not pull up all the new flooring (over existing floorboards) as it is tongue and grooved, glued/nailed.

The boiler got topped up to 1.5 bar on 11/11/09 (cold) and at 10/12/09 it is at 1.2 bar (cold).

Any suggestions what could be causing the leak, how to locate it and what I should do.

Many thanks

 

[twgas]

I would take all the plastic caps off the rad valves and dab around the glands with a tissue, check the iso valves under the boiler, tie/tape a plastic bag over the prv pipe, check all the bleed nipples etc. 0.3 bar a month is quite a small leak.

 

[H2O1969]

I would take all the plastic caps off the rad valves and dab around the glands with a tissue, check the iso valves under the boiler, tie/tape a plastic bag over the prv pipe, check all the bleed nipples etc. 0.3 bar a month is quite a small leak.

Ok thanks for this. What are the iso valves and the prv pipe please?

BTW I have plastic flexipiping under the floorboards. I have informed that if these were leaking, then the pressure drop would likely be a lot more.

 

[twgas]

iso(lating) valves, p(ressure) r(educing)v(alve)

 

[H2O1969]

Thanks for the advice. I have checked the radiator valves and it seems dry under the boiler. I'm not sure where the prv pipe is. I have included a picture if that helps.

Untitled

• H2O1969
• 12 Dec 2009
• 1

 

[twgas]

prv is far right, it should terminate outside, either near the ground, turned back to the wall or it may have a mushroom shaped thingy on the end.

 

[H2O1969]

Ok thanks. I have fastened a bag to it and will check it tomorrow.

 

[H2O1969]

I followed the advice given and detected no leaks.

However, today, 5 mins before the CHS was due to come on I noticed a weeping valve at the top of the towel rail downstairs. It was such a tiny amount of water which 20 mins after the CHS had been on, it has evaporated.

I guess it is only leaking when cold and has gone undetected because any trace of seeping water had vanished.

I will see about getting the nut tightened up. It is 21mm I think.

Again, thanks for advice and hopefully this is the cause of the pressure drop (which has been occupying my mind and time).

 

[spikebmth]

I would think you;ve found it!

 

[twgas]

I would think you;ve found it!

I concur.

 

[H2O1969]

Fingers crossed. I'll tighten when cold and when I can get a suitably sized spanner. Or I could use my contract with Homeserve.

 

[twgas]

Go the contract route, if you try it yourself and something goes wrong you could have an unforeseen cost, if the insurer's engineer cocks up it's down to him/her/them.

 

[H2O1969]

Thanks for the excellent advice twgas and for cocurring spikebmth

The advice re contractual route clearly comes from a very wise head!

Cheers again.

 

[twgas]

you'll have me blushing in a minute

 

[H2O1969]

Well, 2+ years on and I still have a very minor leak which has still not been detected despite other more noticeable boiler leaks and replacement parts to the boiler.

Any ideas?