Basement bath DWV questions

Great forum here Terry ... I've been lurking and reading posts for quite a while. Now I'm about to tackle my own project and would love some advice.

Getting ready to bust up some concrete (once I finalize this plan) to install the DWV for a basic 5'x9' basement bath (I'm actually moving a "primative" bath about 10' from where it was initially installed. I've attached a picture, since it's a lot faster than trying to explain it.

What I do know is in my favor:
* Plenty of depth, main 4" line is 12" below floor (3" slope over 14')
* I can tap into the old 2" vent line without too much difficulty

What I don't know:
1) Is 3" OK for my main line, or is 4" req'd because I'm in the basement?
2) Does the 2" wet vent thru the lav suffice for the whole set-up?
3) Does it matter that the commode is "upstream" from the rest?
4) My plan would be to tie the 2" lines from lav and tub into the 3" line with a 3x3x2 wye rolled over with an 1/8 street elbow--is that the best technique?

Any advice would be appreciated. Thanks ... Phil

1)yes
2)no, see below
3)no, unless downstream traps are vented. entire bathroom can vent on a 2" (tie the additional 1 1/2" vent into the 2" you propose)
4)yes, roll the wye's "up" so the leg of the wye is 45° or less from vertical, use the 45° elbow to roll the pipe back down to make it more horizontal


Adding an additional 1 1/2" vent for the tub would make your installation legal where I am.



Looks like you've been paying attention during your lurking. Not many can grasp wet venting a cellar coset through a lav. Good Luck.

tub vent follow-up

Thanks Dubldare, I confess that the whole venting issue perplexes me more than any other code compliance item in my home fix-up world. It THINK it should be pretty straight forward to put a 1-1/2" vent up the wall at the head of the tub and tie it all in.

As to location of the stub-out in the tub box (DAP?) ... I understand to create a 14" square with room to move the p-trap around a bit. But I look at the tub rough ins (Kohler villager, quite standard) it is not real specific. I presume I need to stub it out a few inches to one side or the other of the box? If it is dead center how would you swing the p-trap to make the connection?

1. Does my little visual of the dap box and incoming drain line make sense?
2. Not to be dumb, but putting a sanitary T on its back is OK to run a vent straight up through the wall, correct?

Tks again for any advice. Phil

You could make the trap/vent placement less complicateted by moving your 3x2 wye for the tub farther downstream. This will allow your vent to be placed closer to the inside tub wall, giving you more room for your valve.

I don't install the trap until setting the tub. Getting the waste line close to where the trap will be is often the best you can do. I show the line entering the box at a 45. This will allow for another 45 and trap swing for fine tuning.

As far as the san tee on it's back, that is legal for venting where I am. Some places require a wye/eighth to used instead.

basement tub vent

Thanks again Dubldare. I think I'm understanding it pretty well now -- the whole 3-D working in the tub box was hard to picture at first. I see how moving the wye down stream a bit will help put the vent in a convenient place. Once I get working I'll come back if I have any more questions. Phil.

"simple" backfill question?

OK ... six months later and I've busted up the concrete and dug out my trenches! (Other things delayed this project).

I've got nice red clay here and have calculated my 1/4" per ft slope. What is the best way to backfill around the plastic PVC drain pipe below the slab?

Rock free clay tamped around it?
Sand?
Gravel?

Even though the existing 4" slab (c 1948) was poured directly on top of the clay, I plan to put a few inches of gravel down before I pour the new concrete.

Hopefully I'll have a nice new roughed in bath by Halloween. Thanks for any advice. Phil.