How much water should come from my combi condensate pipe?

[MisterBoy]

We've recently had our condensate pipe replaced and rerouted as it has issues, it was bodged into the gutter and now runs down the side of the house so I can see it.
My boiler is running and I can see a constant flow of water... Not a solid stream but almost, certainly a very fast drip.

Is this typical or something to be looked into? Is water supposed to come out at all normally, or is it more like an overflow?

 

[Madrab]

Really depends on the boiler and type of condi trap it uses, some are just basic 'u' bend type traps others are auto syphon types, the former can run constantly if the boiler is condensing.

 

[Jajodu]

That's how it works, will only drip while the boiler is in use and for a short time after.

 

[Madrab]

That's how it works, will only drip while the boiler is in use and for a short time after.

If it's an auto syphon type it won't run constantly .... It'll fill up, gets to the spillover level and then the syphon action empties the trap to a low level, then it stops emptying, it'll repeat that till the boiler shuts down.

 

[MJN]

Constant* dripping is a good sign as it shows that the exhaust gases are being cooled sufficiently (and therefore latent heat recovered) resulting in condensation being formed.

*If it constantly drips even when the heating is off (and has been off a while) then that's a different story and may be indicative of a corroded heat exchanger or similar leak inside the combustion chamber causing system water (not condensate) to pass.

 

[MisterBoy]

Thanks - sorry I forgot to add the type (Baxi duo tec Combi). I haven't noticed it dripping when the boiler isn't running but as I've mentioned in a previous thread before we have ongoing issues with water appearing in the 'top' chamber behind the main removable front cover. We thought it might be the condensate pipe backing up as it was quite dodgy but replacing brand new with a vertical drop the issue remains (though less) and obviously frequent water there is now starting to look messy and could cause more problems.

Is it very unsafe to run the boiler with the cover off, to watch and see where the first drop of water is coming from? Once it's wet inside everything is damp but if I dried it out and could then sit and watch, it might be informative - but only if it's fairly low risk. Clearly I'm not going to touch it while running, just observe.

 

[ianmcd]

Is it very unsafe to run the boiler with the cover off, to watch and see where the first drop of water is coming from? Once it's wet inside everything is damp but if I dried it out and could then sit and watch, it might be informative - but only if it's fairly low risk. Clearly I'm not going to touch it while running, just observe.

Turn it off, you can not see condensate even with the cover off, you have a leak, absolutely nothing to do with the condensate

 

[MisterBoy]

Turn it off, you can not see condensate even with the cover off, you have a leak, absolutely nothing to do with the condensate

The plumber's thought previously (if I understood him) was if the condensate pipe was blocked it could back up into the boiler? But like I said that was already checked so my query is how to find where the leak is, since it doesn't drip anywhere when it's turned off, and when it's all wet everywhere you can't see the source. So I wondered if you dried it all out and then turned it on, you might see it start to weep wherever the problem is. The plumber doesn't want to change expensive parts trial & error.

 

[ericmark]

An interesting question, the more condensate per measure of gas, the better the boiler is working. I am sure there is a formula which will tell you, but not sure how to measure.

 

[gas112]

Thanks - sorry I forgot to add the type (Baxi duo tec Combi). I haven't noticed it dripping when the boiler isn't running but as I've mentioned in a previous thread before we have ongoing issues with water appearing in the 'top' chamber behind the main removable front cover. We thought it might be the condensate pipe backing up as it was quite dodgy but replacing brand new with a vertical drop the issue remains (though less) and obviously frequent water there is now starting to look messy and could cause more problems.

Is it very unsafe to run the boiler with the cover off, to watch and see where the first drop of water is coming from? Once it's wet inside everything is damp but if I dried it out and could then sit and watch, it might be informative - but only if it's fairly low risk. Clearly I'm not going to touch it while running, just observe.

the condensate pipe inside there is a corrugated grey pipe and it splits in the corrugations and needs replacing with the new solid black rubber ones . get a new plumber

 

[Johntheo5]

An interesting question, the more condensate per measure of gas, the better the boiler is working. I am sure there is a formula which will tell you, but not sure how to measure.

Will try and calculate it.
"wet gas" loss in nat gas is ~ 10% and 1kw boiler output at 85% efficiency requires 1.18kw, 10% loss = 0.118kw = 425kj. latent heat of evaporation is ~ 2256kj/kw say 2256kj/litre. condensate = 425/2256, 0.19l/kw boiler output if fully condensing. A boiler at 10kw output will condense 1.9LPH if fully condensing, so maybe allow for only 50% condensing so maybe 1.0LPH per 10kw boiler output??.

 

[MisterBoy]

So we thought this was a bit better as no leaks and far fewer problems so I've been lax at getting someone out, but it's clearly still wet and now starting to get messy.

I am 90+% sure the water is coming from this threaded section below the main combustion unit, you can see the thread is visibly wet...I dried it and this is damp again soon after. So surely that's where it's coming from.



I've suspected this was the ingress point before but when I've asked I was told "there's no way water could be inside there". Could there be an actual leak inside the sealed unit, if not what ARE the possibilities? Surely can't be too many.

I don't know what's relevant but we've already raised the condensate pipe and there has been zero reason for over a week. The water coming out seems very clear, not like the CH water which is a bit mucky.

 

[MisterBoy]

In fact it's actually damp above the thread. Hard to get a good photo but it seems it's not maybe the thread leaking but something higher up?

 

[Johntheo5]

Can yo get a photo from underneath the boiler of the pipe exiting the casing bottom.

 

[Madrab]

If that's where I think it is - at the base of the venturi - then that's the gas pipe. You shouldn't really be in there and would advise you leave it alone (as was suggested earlier) and get a new engineer in to strip it down and find where the problem lies.