Worcester 35 CDi pressure drop

[smule]

I've just moved into a new house and have had the central heating drained while I've worked on the pipework. I've just refilled it and am noticing a slight pressure drop - about 0.1 of a Bar overnight. It is a Worcester 35CDi combi.

I can't find any leaks on any of the pipe work I have seen. I'm worried there could be one in some inaccesible place.

Any advice on how to locate the problem. Does that Fernox leak sealer work? Should I disconnect the loop in?

 

[ChrisR]

Disconnect the filling loop, check outside to see if the pressure relief is dripping.
Check inside the boiler (or elsewhere) for auto air vents, which can seep water out.
Other common points are rad valve spndles.

 

[Dan Robinson]

Fernox LS1 or Superconcentrate is pretty good stuff, but no substitute for finding the leak and repairing it.

 

[croydoncorgi]

Probably a bad idea to put leak sealer into a combi unless you're desperate!

Are you SURE there's no water coming out of the PRV discharge pipe (on the outside wall, under the boiler)?

Also, there may be a leak across the secondary heat exchanger. Do you notice the indicated pressure going up as well as down? Do you know what your local mains pressure is, approximately?

 

[smule]

OK lads. Thanks for all the speedy replies.

I'm not sure what the mains pressure is but when I was watching the pressure today I noticed when there was a demand on the hot water from the kitch tap it affected the pressure.

The pressure was going up when it was heating the rads.

I can't see any discharge from the pipe on the outside wall or see any signs of a leak elswhere on the boiler.

I've disconnected the loop in so I'll keep an eye on it.

I was thinking of joining the British Gas homecare anyway. Is this something they would sort out as part of that agreement? Would they search out the source of the leak even if it was in the system?

The previous owner of the house was topping the pressure up daily. Losing half a bar overnight. Since then I've found a few leaking rad valves and replaced them. I thought that would sort it out but it hasn't fully.

 

[Dan Robinson]

I was thinking of joining the British Gas homecare anyway

Save your money....


As the boiler heats up and the pump spins the pressure guage will move...

 

[chrisey]

Heating enginreers/corgi reg installers on this forum should not be giving information to the layperson to look in boilers for leaks etc. You should all know the consequences involved. Keep it simple Regards chrisey

 

[mikej2005]

Does that Fernox leak sealer work? Should I disconnect the loop in?

I've just had a 37CDi combi fitted and I'm pretty sure I remember reading in one of the manuals that Worcester recommend you don't use leak sealers like that.

 

[mikej2005]

I was thinking of joining the British Gas homecare anyway. Is this something they would sort out as part of that agreement? Would they search out the source of the leak even if it was in the system?

They have different levels of cover and the cheapest (£13/month) only covers the boiler and controls. You'd need the next level up (£17/month) and even then you'd be advised to read the small print to check that something like that would be covered.

 

[pannierstan]

I've just moved into a new house and have had the central heating drained while I've worked on the pipework. I've just refilled it and am noticing a slight pressure drop - about 0.1 of a Bar overnight. It is a Worcester 35CDi combi.

I can't find any leaks on any of the pipe work I have seen. I'm worried there could be one in some inaccesible place.

Any advice on how to locate the problem. Does that Fernox leak sealer work? Should I disconnect the loop in?

Had to replace a few Heat exchangers on these CDi's as they leak internally and the water disappears down the condensate drain.
If you can try isolating the flow and return connections under the boiler (the 22mm pipes at either end) and then wait for a few days at least.
You can still use the hot water in the mean time by the way!!
If you notice the pressure still dropping then the leak is on the boiler. If its not dropping but does when you reopen the valves then the leak is elsewhere on the system.
From my experience they tend to leak when warming up and not when cold or very hot.
Heat ex is expensive and needs a Corgi as the boiler has to be recommisioned including flue gas analysis.

Good luck

Stan

 

[clf-gas]

Fu**in numbties
Dan's the only one with any knowledge

 

[clf-gas]

OH Sorry and you too Stan

 

[Dan Robinson]

Careful I have two doors to get through before I reasch my bed...

 

[clf-gas]

Thats cause you is a big fella

 

[Dan Robinson]

Thats what she said