Hello,

I current am installing a bathroom on the second floor of my home. There is a 3" vertical vent that runs underneath what is to become my toilet, then turns 90 degrees up the wall and through the roof. Can I use this vent as to drain the toilet? (It has sweeping 90s and I believe there was a bathroom planned for this area)

Thanks!

-A

You propose to make a second floor vent stack into a stact vent and still keep the lower floor bathroom group venting in it. You can't do that.
To make that work you would have to cap off the connection of the first floor bathroom vent and run a new vent from there up through the roof.
Another way would be to run a three inch stack vent down to the main and tie the second floor into that. It will then extent up and revent back into a existing roof vent in the attic. Good luck, Tom

Speedball 1, you are assuming that the 3" stack is venting a 1st floor bath. That's not necessarily the case. In Alabama a 3" stack off the main is required. If that vent is a dry stack it could be used as waste line/vent. You would have to check with local codes. Triple T2 Master Plumber