I inherited a small mess that I am cleaning up. The basement washing machine and utility sink wet vent into a 1-1/2" riser that goes thru the concrete slab, w/ an air admittance valve. I am stuck with that situation (these were installed by a plumber for the previous owner.) I don't know the DFU but if not large enough I'll change the AAV (or add a second.)
The W/M trap was cracked -- see pix -- (and the drain for the U/S is in a horrendously stupid location thru the legs - and notice the copper to galvanized to pex -- so I am starting anew with it all.) I may finish that room at some point, so might install a W/M supply/drain box - not sure.
Q1: The wye for the U/S drain - isn't that a No-No -- should have been a San Tee??
Q2: I'll locate the W/M riser/trap 12-18" above the slab - should I use 2" (and also there to the slab) even though the thru-slab is 1-1/2?
Q3: I plan to use an S-Tee for the W/M drain. OK?
Q4: Concerned w/ the high W/M flow/pumping - do I need to back vent the W/M drain (or I could add a second riser/AAV??)
Q5: Any reason to lower the U/S drain and stack the S-Tee above the W/M S-Tee (I'd think it's best to keep as much separation as I can)?
Q6: What's the reasoning for the W/M trap 12-18" and a max 30" riser (just curious)?
Q7: This pic floats around - isn't the wye for the W/M a no-no? Or is that only with a wye on the trap arm itself? And the sink drain looks too steep - is the vent entry below the trap weir level?
Thanks for looking at this!