Hi, I am completely remodeling our first floor bathroom. I have a question about venting it. Our main drain pipe leaving the house is 3". I would like to have the main vent stack to be 2" so that it can fit in the wall. It will serve a Toilet and a Bathtub, Once it gets to the attic I will transition it to 3" and tie in a 1 1/2 vent from the lav, and a 1 1/2 vent from the shower in the same bathroom. I will also tie in a 2" vent from the basement that serves a toilet, lav, and shower. Will this suffice as my main vent exiting the roof at 3" the same as the main drain pipe, Or does it need to be 3" from drain pipe?
Thank you very much.