Combi condensate - trap/vent/valve?

[RJH]

The condensate from my combi boiler drains via a connection at the kitchen sink waste. Whenever the sink is emptied (etc.) this produces a bubbling sound from the boiler, which I'd guess is caused by suction acting on the condensate reservoir/trap inside the boiler.

I'm not sure if it's doing any harm, but was thinking about the best way to stop this happening, short of relocating the drain pipe. Suggestions please . .

[John J]

Divert the condensate into a washing machine standpipe trap?

[Harry Bloomfield, Esq.]

RJH brought next idea :

Add a separate trap (a U in the pipe), just for the boiler condensate, or take it out through the wall and to the drain separately.

[Tim+]

I don?t think it?s doing any harm. I don?t think the condensate trap is there to provide any sort of fume barrier, it?s just to turn a steady trickle of condensate into an intermittent rush (which is much less likely to freeze up). If it?s making a bubbling sound this would imply it?s just drawing air through condensate that is still in the trap rather than emptying the trap.

I could be wrong though.

Tim

[Davidm]

I was told by the people who service my Worcester Bosch ch boiler that the condensate trap is there to both prevent fumes (CO) escaping from the boiler and to provide bursts rather than dribble of condensate to resist freezing if being routed outside.

[John Rumm]

The condensate trap is in effect connected to the inside of the main HX, so it *is* there to keep combustion by products contained as well as allowing for a measured discharge.

Chances are it will not empty the trap completely - so the risk is low.

Personally I would take it to an open top stand pipe like one would use for a washing machine or dish washer. (which is where I did take mine in fact - it shares a stack with one of them)

[RJH]

Thanks everyone. Looks like it's going to part of a larger project to install a standpipe for the washing machine and dishwasher. Added to the list :-)

[John Rumm]

I do it by using a slightly shorter standpipe with a swept T fitted to the top to bring it up to height. Take the condensate drain into a fitting reducer, thence the side inlet of the Tee. The hose from the WM etc can then poke down the top open end of the Tee.

[RJH]

Thanks, yes, I was wondering about where the condensate pipe would go. As it is there's a dishwasher and washing machine, so already quite a lot going on. But the swept T would do it.

I think the biggest problem, is going to be fitting it all in. There's no space behind the appliance(s) so there's going to have to be some kitchen cabinet surgery.

FYI, at present the 3 drains - condensate, washing machine and dishwasher - all feed into the kitchen sink waste at various points. /Seems/ to work. My main concern with the arrangement isn't in fact the condensate - it's the washing machine. That drains using an extraordinarily powerful pump from the cellar. Just a matter of time before it blasts the feeble push-fit to pieces. Mind, it's lasted 10 years so far . . . so far.