Draining bathroom group into one vertical stack (UPC)

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Brian Nagy

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Gardena, California
I'm converting a small home office space in my house into a second bathroom for my mom. There's only one configuration possible for the fixtures in the space and only one non-structural partition wall through which I can run a 2" vent up from the crawlspace. The 3" building drain runs underground and emerges under that wall. I figure the most efficient DWV solution is a single 3" stack on top of that drain terminus. I am bringing the lav drain down through the floor in the vanity cabinet and venting it separately. I've got the w.c. trap arm dumping into the stack at the lowest level. Thus, the w.c. is vertically wet vented up through about one foot of 3" pipe into which the other fixtures drain. The lav drain drains into the stack above the w.c., but as I noted, it is separately vented. The shower trap arm is the uppermost connection to the stack, so it is not being wet-vented. Atop the 3" stack, the common 2" dry vent (24 DFU capacity) supplies air to the shower (2 DFUs) and w.c. (3 DFUs). At the lower end of the building drain, I have a 2-way cleanout, so I don't require a cleanout at the upper terminus. I've got a cleanout for the lav drain in the vanity cabinet, and a cleanout access in the 2" vent atop the stack. I'm sure it will work perfectly well, but is it code-compliant? In my reading of the code it is, but the California plumbing code (based on UPC) is clear as mud.


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