Imagine a Vertical 4" pipe coming up the basement wall and making a Wye about 1 ft from the ceiling..
Left to the 2nd floor toilet and sink.
Right is going to the 1st floor toilet, about 2 ft away. (and 1st floor sink and bathtub)
Up against the ceiling is a 2" vent pipe coming from the basement plumbing and heading to the roof. (turning into a 4")
So, if I connect the waste pipe up to the 2" vent pipe, would that satify the venting for the 1st floor toilet?
This will be a 2" from the 4" waste, to the 2" vent. But it will be about 1ft long.
Is this a satisfactory vent?
It sounds logical, but I've never seen is done like that.