Combi CH pressure drop.

[Ret.]

I had my conventional gas boiler replaced two years ago with a WB condensing combi. System has been fine ever since, but yesterday when I checked the system pressure guage on the boiler I noticed that it was almost down to the red.

I bled all the rads (just a bit of air in the 'ladder' towel rad in the bathroom - the rest ok) and then re-pressurised the system.

Today the pressure has dropped again - not a huge amount but it is clearly dropping.

I have checked all the rad connections and bleed points and there is no sign of a leak anywhere - so any leak must be under a floor somewhere.

Bearing in mind that I have laminate flooring in lounge, kitchen, and one bedroom - and Karndean flooring in the bathroom, I'm horrified at the thought of having to lift flooring to find a leak.

Is there any way to isolate the location of a leak - or am I stuffed?

[ARWadsworth]

Start off by tying a plastic bag over the vent pipe outside. The water loss could be from there. If it is then the pressure release valve is leaking.

Even if it is not the PRV it would also be worth trying a leak sealant before ripping floors up eg

Cheers

Adam

[Muddymike]

This one might be better.

Mike

[Ret.]

Brilliant. Thanks for that Adam - why I didn't think of leak sealants I don't know. The leak is clearly not serious or I would be able to watch the pressure drop. The leak sealant is likely to plug a tiny leak very effectively.

Phew - thanks again!

[Ret.]

>

Indeed. I replied to Adam before following his link - only to find that it was to an external leak sealer compound. If I knew where the leak was, and could access it, there wouldn't be a problem.

This internal sealant should do the job.

[ARWadsworth]

Probably better to use the stuff Muddymike linked to as I posted the incorrect link:-)

Cheers

Adam

[ARWadsworth]

>

Certainly will be better. Guess who was on the beer last night and cannot copy and past correctly this morning?

Cheers

Adam

[Ret.]

>>

>

LOL! Not to worry Adam - at least you brought up the idea and I'm grateful to you for that.

Having said that, I've just gone around all the radiator valves again and found one behind the lounge sofa that I had only peered down at before. It has clearly been weeping, with water stains down the pipe. I've tightened it up - re-pressurised the system - and I'm keeping my fingers crossed!

[ARWadsworth]

>>>

>>

And don't forget to check the PRV by putting a bag over the blow off pipe. If things have worked OK for two years it could easily be the PRV that is at fault. It only needs a drip a minute to bring the system to zero pressure in

24 hours.

It might also be worth adding some inhibitor after you have cured the leak. A few pounds to stop internal corrosion of the system is a wise move IMHO.

Cheers

Adam (Who will be going to the pub again tonight for the England match)

[Martin]

< snip >

Let's hope that's all it was ... :-)

[Ret.]

>>>>

>>>

Yes - I'll certainly do that.

It does have inhibitor in at the moment - but having to introduce fresh water to re-pressurise will no doubt have diluted it. I have half a bottle of inhibitor left - I'll top up with that.

I've just checked the pressure guage again and I think it's still creeping down, damn it. So I may still have to resort to the 'radweld' technique!

[Ret.]

Not looking good at the moment - but still maintaining a watch on the guage!

[AJH]

I'm not a CH engineer but I maybe you should check with your boiler manufacturer before putting a leak sealant in to your system. It sounds like the same principle as the car old radiator sealer, if there is a chance that it could get where it would be better off not getting then I think I would prefer to keep my new boiler 'clean' and try and locate the leak by normal means first. AJ

[Ret.]

Yes, valid point. I've just checked the pressure guage this morning and, thank goodness, it's still holding up - so it looks as though the 'weeping' valve connection in the lounge was the culprit.

Thanks to everyone for your suggestions however.

-- Kev