Hello,

I'm remodeling my bathroom here in California, and the group has been
very helpful with a few questions I've asked so far. Right now I'm
trying to finalize the layout, and I have a couple questions on sizing
the soil stack and plumbing wall.

The plumbing wall will service a water closet and lavatory on each
side of the wall (back-to-back fixtures). I'm planning to locate a 3"
soil stack in the wall between the two toilets and service the
lavatories with a 1.5" drain/vent that revents to the soil stack in
the wall (the drain will connect in the ample crawl space). So:

1) Should I use a 4" soil stack? 3" is adequate in terms of fixtures
units and I don't have any problem with the aggregate vent area
rule. I've also heard that 1.6 gallon closets perform better with
a 3" drain line.

2) With a 3" stack, is it reasonable to frame this wall with 2x4s? My
understanding is that 3" ABS is 3.5" O.D., but the stack will not
intersect any studs. I assume it is OK to completely sever the top
and bottom plates where the stack passes through. As for the
reventing, the wall is nonbearing, so I can bore a hole up to 2" in
the studs, and the O.D. of 1.5" ABS is only 1.9". Boring for a 45
degree vent run will lengthen the hole required, but the width will
still be 1.9"; I assume the extra length will not be a problem.

Thanks for all the help.

Cheers, Wayne