2nd story bathroom, drain &vent, please help!!!

serik

Hello everyone!
I am adding a second story bathroom on top of the 1st story bathroom.
1st story bathroom has a 3" drain under the slab, for the toilet, toilet is vented thru 2" pipe and sink discharges into this vent. So it looks like this:

I
I ---U lv
I /
I/
I
======U WC

=== is a 3" pipe, --- is 2" pipe, I is a 2" vent and U is a water trap,

I plan to cut the 3x3x2 tee out, replace it with 3x3x3 tee and run a 3" stack up to the second story, so i can drain a toilet down. The sink and a toilet will be along the same wall and a shower 8' away.
I was hoping to make it simple, run this 3 inch stack to the 2nd floor, it would change to 2" at the tee between the joists and 2" will serve as a vent for both 1st and 2nd floor toilets.

I am not sure if I can drain my sinks and shower into the same stack. and also if i need any extra vents. The way i drew it, that 2nd story shower and a sink will have a separate vent and will drain below 2nd story toilet. Should I extend this 2" stack all the way down and try to drain it into horizontal 3" pipe before the 1st floor toilet vent? I am looking for the simplest solution, horizontal pipe is under the slab and I want to avoid a lot of concrete braking


I would highly appreciate an advice from the professional. Our project is way over budget and we cant afford a licensed plumber to do the work. I pulled a building permit and it means the plumbing will have to pass an inspection.

Thank you very much for your input!

baleworker

Here is a better diagram, so you guys can see what i am up to.
Please, let me know if it meets the code and if it will work without any issues.
Thanks a lot!

rjniles

No it will not meet code. You are creating a wet vent for the first floor drains.( Drain water from the second floor is flowing past the first floor vents.) Run the new 3 inch line from the second floor drain back to the 3 inch main drain (horizontal pipe). Tie in the second floor vent into the 3 inch going thru the roof.

Not sure your existing first floor arrangement meets code either, but it existing.

serik

ok ,so i guess i have to preserve a separate vent for the 1st floor toilet and sink, right?

I updated a diagram, also, what fittings should I use?
The whole horizontal 3" pipe is under the slab, and that new vent would have to be under the slab too and have a small horizontal section till it meets the wall. How can I add a horizontal 2" vent to the horizontal 3" drain?

Also, is it OK to have a shower trap 8' away from the vent?

Thanks!

rjniles

I would tie the second floor SH(ower) into the vent. And tie the first floor BT (tub) into the vent. Use a 3/3/2 tee.