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Discussion Starter · #1 ·
I'm remodeling a bath/laundry area in an old existing detatched building.
All lines will be ABS at 1/4" per foot. The back-to-back LAV's will have a double wye connection. Cleanouts are not shown but will be added.
I hope the pic isn't too hard to see.

Please let me know if there is a better way.:)
I've got a few specific questions...

1. I know the sink and washer should have their own vents, but can the main stack vent the utility sink and washer since the run is only 5'? I'd rather not hack the existing double 2x4 top plate out for a vent if the stack can do the job. Maybe I could just add an AAV to the sink if necessary?

2.Does the wc need a combo where it attaches the stack, or should I use a sanitary tee since it is also used to drain the (vented) LAV?

Thanks for any feedback!


· Premium Member
13,112 Posts
I think you're UPC- TO answer your questions:
1.You can re-vent back to the stack or stack separate trap arms for each fixture as long as they're less then 5ft
Can not use AAV if a vent thru roof is possible
2. Tee is fine but your lav line is now considered the vent for the wc. So it must be 2" underslab as well as through the roof.
Use a "fixture cross" or stack tees for back to back fixtures- not crosses
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