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?