I have an older home and am putting in a bathroom upstairs. I am redoing the plumbing also as it is old galvanized plumbing. I did all the water lines in pex except for one spot where there was a set of copper to the shower which I had already upgraded so i just connected the pex to the copper. now I want to do the drain lines. The problem I have is the main stack runs from the basement floor right up to the toilet. They then have a 2 in vent that comes out of the main and runs up to the attic. It used to tie into an old chimney but that is gone now. Anyway none of the fixtures tie into this vent. They all are close to the main stack about 6-7 ft away as the bathroom and kitchen are back to back there are no long runs and the bathroom I'm putting upstairs is right above the one below. Most pictures I look at have the main stack running straight up through the roof where this one just goes right to the toilet. I have an idea on venting everything but I'm not sure what to do here with the main stack vent. Im going to cut it down to add pac for the new drains and upstair drains. Can I just add a 90 or y and run the vent up and tie the other fixtures to that.
https://goo.gl/photos/9TGpXikC6MD46B92A
https://goo.gl/photos/9TGpXikC6MD46B92A
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