advice req for running 2 showers into one 50mm waste pipe

[JohnnyF]

Hi,

we are having our bathroom redone to divide it into an ensuite and main bathroom. We'll end up having two showers side by side.

The joists mean the wastes have to run above floor level. To hide the waste rather than boxing it in we had a double stud built with a 65mm gap to run the waste in. The builder reckoned this was plenty as both showers would run in the same 50mm waste pipe (approx 1.8 m run to the external wall).

I've read up on it on the net and I've seen it is best to have sanitary ware with their own individual wastes. If we were to run two showers (not power ones just going to be mira code showers) into the same waste would we encounter problems with smells, gurgling noises and one shower backfilling the other shower?

If so is there anyway to avoid this still using the one 50mm waste?

Also does the 1:40 gradient have to be strictly adhered to or could you get away with a 1:30?

Thanks in advance

 

[breezer]

1:30 is steeper* than 1:40

*depends which way you look at it

 

[markplumb]

if your worried about smells use hep O traps (might have the name wrong) long plastic compression coupling with a condom like rubber sleeve inside. water can only flow one way through it and the rubber bit closes to stop any air once there is on water flow.

edit: hepVO

 

[JohnnyF]

sorry my maths is letting me down

I meant for the gradient to be shallower - so I guess something like 1:50.

So if I use hep VO traps on each shower and keep the gradient at 1:40 then I shouldn't have any problem with having two shower running into one 50mm pipe?

cheers

 

[markplumb]

not sure if a building inspector will accept them in place of a deep seal trap. i haven't had any problems with them.

 

[chrishutt]

You'll be fine with normal shower traps with 50mm deep seal sharing a 50mm waste pipe. The pipe will never run full bore even with a fair old gradient on it, no no syphonage problems. Just make sure that the two shower wastes join together with the sweep in the right direction and provide easily accessible cleaning eyes for the main run of the waste pipe since the slow flow will leave deposits in the pipe which will need mechanical cleaning from time to time.

 

[JohnnyF]

Cheers chris. So you would advise burying these in a stud wall if we potentially need access.

We are having a false ceiling put in the room below so I might ask the builder to lower it more so the wast pipe can run under the old joists but above the new ceiling. That way there should be enough gradient, I can run seperate wastes for the showers and basin and if I ever need acces I can just lift the floorboards.