[stubborn1]

any thoughts?

 

[TheEplumber]

I'm adding a small 1/2 bath to my basement. See the pic below. The 4" main drain line is exposed and intersects the bathroom diagonally. I happened to luck out that the toilet rough in lines up exactly on the center of the existing line - 12" out on the framing square in the photo.

I'm not exactly sure how to vent the toilet. I will be installing a sanitary tee to connect the lav along the line of the level which will also serve to vent the lav. Will this vent be sufficient to take care of the venting needs for the toilet?

Also - there is a chance I'll be adding a bathroom upstairs in the near future almost directly above this bathroom. Instead of coming off the main line with a 2" for the lav, I considered bringing a 3" line vertical to serve as a future drain stack. Right now, I would cap it with an AAV. Here's my issue - if I use this 3" as a drain in the future, the vent would become a wet vent to the basement bathroom. Would this be legal or would I need a separate vent line for my basement bathroom?

Thanks in advance for the help.

In regards to your toilet and lav- you can't put san tees on their back. Must be wyes.
You can't wet vent multiple floors. However, you could wye off the base of the proposed 3" for the first floor lav, continue up with its vent and tie it into a second floor vent.

 

[stubborn1]

Thanks for the help.

In regards to the Y fitting, I only have 6 1/2" from the top of my slab to the top of the 4" CI pipe. With the toilet laying out directly on top the existing line, I don't have a lot of room for fittings. I'm guessing by the time I turn 90 degrees vertical from the Y that I'll be sticking above the slab. Is there any other way to configure this? Otherwise, I'll need to change the location of the lav and toilet to make the piping work.