How much condensate does a boiler produce?

16 Jun 2006
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United Kingdom
Hi all

The other day I noticed a leak on the elbow where the condensate pipe exits the boiler- it was about one drip per second. I put some MS polymer around the join and the leak stopped.

The next morning I ran a bath. The water was cold.

I checked the boiler, the fault code said there was a problem with the condensate. I peeled the MS polymer away and allowed the water to drip out. I reset the boiler and checked the nearest tap. The boiler fired up. I went up stairs to run the bath again. Again it was cold.

I am guessing that the condensate pipe was fully blocked, hence the drip at the elbow.

A plumber has since dealt with it and all is good, but I'd like to know roughly how much a condensate running a bath would create at this time of the year (with the heating off). I guess it varies from boiler to boiler our's is a Worchester Bosch, approx 15 years old in a two bedroom house.

Thanks in advance
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Depends on the flow temp but it's quite an amount really. Enough to need clear pipe.
When I was doing up my place, I just had the boiler (condensing combi) installed, but hadn't finished the condensate properly, so was discharging into a bucket.

I had the heating on all day, (in winter) finished, then went out that evening, forgot to check then bucket... returned the next morning to an overflowing bucket full, mentioned to the plumber who said in cold weather, they can generate lots of condensate.
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How much condensate does a Worcester boiler produce?

When a condensing boiler is in operation it can produce anything between 2 to 3 litres of condensate per hour which needs discharging to waste
Thanks all.

I hadn't realised that they produce so much. Useful to know. Ta
Thanks all.

I hadn't realised that they produce so much. Useful to know. Ta
By calculation, assuming a boiler firing at 25kw will give up ~11% of its heat in latent heat loss so... 25x11%x2200/3600, 1.68kgs (liters) of water or ~ a max of 0.08 liters per kw of boiler output MAX, so realistically perhaps expect about 0.04L/kw output?

Or easier to remember ~ 1/2 a litre of water per hour for each 10kw of boiler output
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Always insist that the condensate trap is cleaned on service - stand over them till it is....My opinion of gas safe engineers fixing boilers is built around the mess that supposed professionals have 3 properties boilers went to lock out in one winter when the marvelous "britsiht" engineers failed to clean out the trap causing the boilers to fill with water, the boilers being the ones they fitted and recommended...mucho boiler banging, white smoke, new pcb's ,raging cold tenants later...

Culminated in a Christmas eve monumental argument and a rage induced removal of the condensate trap,a few litres of water discharge and the britshat engineer running away as in running, boiler fixed.

Just because somebody can do some pipe work that does not leak at a few thousands of a bar does not make them anything other than a tool...there is no shame in getting the manaul out and doing the fault finder....after you have checked the basics.
I'm curious now, what has to be cleaned out of the condensate trap? isn't it just water/acid?
And combustion lots of boilers the trap is just a rubber ball float valve that gets stuck when gunked up...

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