New 2nd Floor Bath above 1st

[jfinke]

I am currently remodeling my kitchen and have the wall between the 1st floor bath and the kitchen completely open. I thought this would be a perfect time to rough in the plumbing for a new upstairs bath I plan to put in after the kitchen remodel is done. There is currently no plumbing on secnod floor.

My questions relate to the proper way to run the DWV. There is a 4" stack running up from the basement to the roof in this wall between the 1st floor bath and the kitchen. The 1st floor toilet is tied directly into that with no separate vent. It's at most 2 feet from the stack. The shower and sink drain down and tie into the stack under the 1st floor (in basement). The vent for these also ties into the stack about 3 feet above the floor. That describes the first floor.

I basically want to install the same bath layout on the second floor directly above the first floor. I have a lot of conflicting info on this. I was going to extend the vents from the first floor all the way up to the second floor about 48" above the second floor and then into the existing 4" stack along with new shower and sink. I wanted to then install a toilet on the 2nd the same as the first. The problem I see with that is the 1st floor toilet is now sharing the 4" stack and I am not sure that is properly vented.

It seems to me that maybe I should just run a new waste stack 2nd floor to basement and tie it into the existing stack in the basement. Then vent the 2nd floor fixtures (toilet, shower, sink) into the existing 4" stack as well as extend the 1st floor venting up to the second floor.

Any help on this is very much appreciated. I have read every plumbing book I can find and have too many conflicting opinions.

Thanks!

[hj]

If you install a new drain line for the second floor and connect it below the existing first floor, then you do not have to do anything to the first floor piping. As long as the existing pipe is not used for drainage the lower level vents can be tied in just the way they are.

[jfinke]

Thanks for the feedback that makes much more sense. The only other question I have then is for venting the 2nd floor fixtures. Can I tie into the existing stack to vent or should I run the new waste stack to the roof as a second vent. I would love to not have to tap into the roof again. From what I am able to gather from my reading I can tie into the existing stack 38" above the 2nd floor. Is that correct???

Thanks again for the reply!