I currently have a 4" soil stack running vertically from the 1st floor to the basement floor near the corner wall of the laundry room I am building.
I want to plumb a sink and washing machine, both about 5 feet out from the corner of the room where the current 4" soil stack is.
I'm wondering if I can tie into the 4" soil stack with a 4x4x2" wye. From there I would run another 2x2x2" wye horizontally and run drain down each wall. With this configuration, both the washing machine and the sink drains would tie together horizontally and then use a very short common 2" line to where they tie into the 4" stack. Is this acceptable, or do I need to have each drain (washer and sink) dump into the 4" stack independently.
I would of course use 2" vents near the p traps on each drain which would tie into the existing 2" vent running parallel to the 4" soil stack.