Bath waste

[phillyshaw]

Currently refurbishing a bathroom and due to limited room between the bathroom floor level and a window below next to the soil stack is it possible to connect the 40mm bath waste in to the top of the horizontal wc soil pipe run before it enters the vertical soil stack???

 

[Best]

If I am imagining it correctly, then Yes.
You can use a 40mm strap boss, or a soil pipe junction with 40mm branch (which I would use normally)
Just take care to use a bath trap that won't be sucked dry.