Does this floor drain need a separate vent?

[Jess Shannon]

We’re about to pour our slab and we’re setting in floor drains to use for the shower. There is a separate 4” pipe coming up just for the shower, and I’ve got a 2” reducer to connect the floor drain straight into it. That 4” pipe goes down about 400mm, turns horizontal and will connect to the main stack outside the building. There will be further ventilation back up the stack.

 

As it’s a 4” pipe will there be enough air flow that it doesn’t need a different vent, or should I run another 2” pipe over to a wall to connect to a vent?

[kandgmitchell]

That's not going to need a separate vent as a 50mm bath waste can run 4m without venting and a shower runs much slower. If that was a WC sat on that 100mm pipe instead of the shower trap there would be no question. However, consider a) access for cleaning the trap and that bit of 50mm pipe plus b) the 100mm branch cannot connect to the main stack closer than 450mm from the invert of the rest bend at the base of the stack.

[Oz07]

Would you not prefer a 4" floor drain? I used one once fits straight inside 4"pipe. 

 

But yeh wouldn't need a vent.