Foul Water Into Roof-Drain Pipe??

[skenk]

Is it permitted to run a new foul water drain (40mm sink waste) into a 4" roof-drain stack?

It's a combined system (victorian) outside the building (rain and foul water combine for flow into sewer somewhere before before 1st manhole). Friend has had conflicting advice from 2 different plumbers (one says it's ok, the other not, not sure how professional either 'plumber' is).

Any advice appreciated.

 

[Agile]

If the vertical is correctly installed AND it really is a combined drain then its OK.

Tony

 

[skenk]

Thanks I'll pass that on. It does seem odd that there are two stacks 2m apart but both plumbers agree they combine underground (so I'm told). Any other comments welcome to add weight (or not).

There's no easy way to reach the bathroom waste stack without crossing the rainwater one.

 

[HERTS P&D]

Do a dye test.

http://www.screwfix.com/p/monument-tools-flourescein-drain-dye/31595?_requestid=613722

Put some of the dye into a bucket of water and pour down the rain gully, then check the manhole to confirm the dye coming through.

Andy

 

[skenk]

Thanks Herts, yes dye I presume (hope) that's what was used. Will ask her to confirm they are defo shared that before doing anything (not my problem... at least it wasn't till I stuck my nose in!). I presume the rainwater stack would need protection from leaves etc entering at the top. Sounds ok in this case (for a sink) but I don't like the idea of a WC sharing a rainwater stack for some reason, or is that just me

 

[Hugh Jaleak]

Rainwater shouldnt be directly connected to a foul or combined sewer, any rainwater downpipes should discharge into a trapped gulley, which in turn, is connected to the sewer. If not connected properly then the rainwater downpipe will act as a vent for the sewer, possibly allowing foul air to escape where it's not wanted.

 

[JimCrow]

Thanks Herts, yes dye I presume (hope) that's what was used. Will ask her to confirm they are defo shared that before doing anything (not my problem... at least it wasn't till I stuck my nose in!). I presume the rainwater stack would need protection from leaves etc entering at the top. Sounds ok in this case (for a sink) but I don't like the idea of a WC sharing a rainwater stack for some reason, or is that just me

The rainwater pipe will be trapped at ground level so any WC branch will have to be after this trap.