Gas condensate drain - internal

[Tim S]

Hi,

Been looking at the Viessmann Vitodens Compact 100 manual. All condensate drain configurations are shown terminating into an open outside gulley, save for one, which is linked in with the rainwater downpipe.

Why can't the drain go into an internal pipe, say a run that serves a washing machine for example, that then terminates into an internal soil stack?

I thought about fumes leakage, but on example shows the boiler condensate drain dropping into an open pipe which couples to a sink drain then leads to an outside gulley. So that seems to contradict the fumes theory.

BCO mentioned he thought they could only go into a gulley - which got me thinking...

Cheers

Tim

[Lobster]

No reason at all AFAIK. Mine terminates into a vented washing-machine-type vertical pipe; although that then runs to an outside gully.

David

[Andrew Gabriel]

Mine runs into the washbasin runaway. One thing I did though was to fit an AAV u-trap on the basin, so the run-away can't suck dry the condensate u-trap in the boiler.

[YAPH]

Assuming the boiler has its own trap (I think most do) then your only issue is preventing the condensate waste from blocking (including airlocking) and condensate backing up into the boiler's heat exchanger. This can cause interesting effects (BTDTGTTS) ;-). Nowadays I often have a short length of

21.5mm/22mm plastic overflow waste out of the boiler dipping just half an inch or so into a 32mm stand pipe, often then reduced back to 21.5/22mm for a run into a proper waste, trapped as necessary to avoid drain smells and draughts back into the building. Depending on the pipe runs the 3smm/21.5mm may form a long shallow U-trap before meeting the 'real' waste (remember that the contents of this are clean, if acidic, water so no problem with depositing crud in the pipes as would be the case with sink and washing machine wastes).

-------- | | | | | boiler | | | | | | | -|------ | |

[John Rumm]

Not that I am aware of... I did mine into a stand pipe inside shared with a washing machine. Its worth having an air break of some sort - but it does not need to be (only) outside.

[Rod]

There is one huge advantage of it going to an internal pipe. Very unlikely to freeze.

[Tim S]

YAPH coughed up some electrons that declared:

Thanks John and everyone else.

The above is more or less as I was planning. The boiler position is above an appliance point (washing machine) and just the other side of the wall from the loo. It seemed obvious to me to run of the 90 degree bend to the loo (the the bend has side entry spigots), through the wall as 40mm, trap then two upstands, one for machine, one for boiler. Both upstands of course will be pipe-dangling-in pipe, so have airbreaks.

Yes, the Vitodens has an internal trap - one of the stages of comissioning is to prime the trap by pouring water in the top flue before final fitting of flue. They do warn that combustion products may escape until the U-trap is correctly filled.

I agree on the pipe freezing problem - which is why I thought it would be better in than out.

I'll have longer a plough through the gas BS docs and see if I can find a written justification in case BCO asks.

Cheers

Tim