Wayne Whitney wrote:

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.

The 1.6Gal closets should not care what the stack size is.
As I mentioned earlier, you may have problems connecting
2 back-to-back closets on 3" stack if using San Cross/Dbl TEE.
Better is 4 X 3 (4" stack/3" branch) and I would ask if they
will even allow this in CA.


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.

Here too, I would go with 2 X 1 1/2" Dbl TEE/Cross (if allowed).
The vent can reduce to 1 1/2".
If you can use PVC, there is a small dimensional advantage
(may not matter).
I don't see any problem boring holes, although you may have
to add stiffeners to the studs.


Thanks for all the help.

Cheers, Wayne