condensation on combi boiler

Possibly failure of the seal in the bottom of the combustion chamber.

IME W-B boilers are prone to leaks any work on them seems to encourage them even more.

It really is worth having a look around the inside of the boiler for the leak. Boilers are running above ambient temperature on almost all their components and so external condensation from external humidity is unlikely.

Thanks Michael. Bosch, component failure after a year! What's the world coming to?

Thanks, Ed. Your opinion of WB fills me with confidence :-) So, running the boiler below full temperature isn't likely to cause it? I'll check out Michael's suggestion and have a general look round. Given the leak is tiny and intermittent, that should be fun.

Contact WB technical support (via website).

Our Greenstar started doing this and they changed its brain- guy said it was a fault which caused it to over-condense (!?) but whatever, it was free, and fixed the problem.

cheers Bax

Was the boiler still under warranty? Presumably it was ok to start with so a brain fault doesn't seem logical. I wouldn't know how old my fault is because it had no work surface under it until recently, and I wouldn't have noticed a few drips on the floor.

The 24i Junior is a non-condensing combi IIRC. The boiler should be hard to get into a condensing regime for any length of time.

leak. Needless to say it wasn't leaking when he arrived, and only spills a tablespoon or so a couple of hours after the heating cycle. As the boiler's new and the leak small, there was no tell-tale evidence. Doing my own detection, at first I thought it was the compression joint on the CH return pipe but I've since discovered it's dripping on there from above, but below the upper section of the boiler. This would appear to narrow it down to the pump, or some connection to the pump. It isn't leaking from the front bit, or the main compression joint but there seems to be a flexible connector going somewhere which I can't see or get to it. I wonder if there are other connections to the pump that might be the source. If anyone has any ideas I'd appreciate it. I'm not about to pay WB =A3220 for a service call

Place a sheet of newspaper below the suspected leak, and look for a damp spot appearing. That should enable you to determine the leak path. Check especially as the boiler cools, but (obviously) don't leave it so long that the spot dries out. I have detected very fine leaks on compression joints by wrapping tissue paper tightly round the pipe - it holds the moisture so you can detect it, rather dripping away to evaporate somewhere.

Phil The uk.d-i-y FAQ is at

I ended up wrapping kitchen roll round the ch return joint. Gets wet, dries out, and that way nothing hits the worktop. Unless the boiler pressure goes down, it can stay that way. Out of sight.....

Hmmm... that's not quite what I had in mind ;-)

Phil The uk.d-i-y FAQ is at