DWV Layout Advice Needed

Can I vent soil stack from the side instead of the top?

I am working on adding a bathroom to the second floor of my home. One problem I've encountered is that there isn't a wall that runs all the way up from the basement to the roof. Instead, there is a 15" jog from the top of the first floor wall to the bottom of the second floor one (represented by the yellow line in the photo). Fortunately, there is a closet just below, so I can run my DWV pipes into that closet. I cannot vent the stack traditionally though, so I've planned to vent it with a separate 2" pipe that will run from the roof, down the 2nd floor wall, into the closet below and attach to the side of the stack (represented by the red line. Just below the stack vent I plan to place the branch waste line for the shower and vanity (represented by the blue line). Is venting the stack this way acceptable?


http://www.legis.state.wi.us/rsb/code/comm/comm082.pdf

View attachment 10935View attachment 10936

I haven't gotten any replies on this forum, so I knew my plan must be pretty out of whack. I went to a local plumbing supply store and talked to a master plumber who gave me a few hints, but wouldn't answer all my questions unless I was ready to drop a lot of money with him (ugh!). I've adjusted my plan according to the information I got, which was:

a) using a horizontal dry line is not acceptable, so my plan to vent the side of the stack won't work.
b) I can fully comply with code without the vent pipe in my diagram.
c) I only need one vent, which must be between the two highest fixtures.
d) he mentioned something about the junction of the vanity waste line to the shower waste line as being considered a wet vent, which allows a single vent to meet all code requirements for distances to the traps.

So... I took out two of my three vent lines out and kept only the one running from the vanity to the roof. This leaves the shower and stack to be wet vented. How does this look to you all now? Do you have any feedback on further revisions I can make? I'm going to send this diagram to the plumbing inspector and see if he/she will help me out too. Thanks for your feedback all!

As near as I can tell, Wisconsin has it's own plumbing code.

That being said, Normally you can wet vent a lav over a toilet, which it looks like you have done. and you have vented the downstream toilet on its own.

The stack vent would be extra if you are wet venting the lav over the far toilet.

Some places allow horizontal venting that isn't washed under the floor and some don't.

When you pull your permit, you should be able to talk to your local inspector.

Woops! I just realized that I uploaded the exact same image as I had in the first post. I've now exchanged it with the new design. In this one took out the vent for the toilet and instead vent everything via the wet vent.