I was wondering if anyone could give me some advice on rough plumbing my downstairs plumbing? I want to move my existing toilet over to make room to add a shower. I've noticed that below slab my sewer pipe is cast iron which is also true of the line that runs to my toilet. I thought I would cut into my main line using a "t" or "y" fitting and run a new abs pipe to my new toilet location. I was wondering should I use 3" or 4" pipe to come up through the concrete floor. If I use 3" I noticed the flange that goes inside the pipe (so it would be flush to the finished floor) is not a large diameter opening .
Should I therefore use a 4" pipe and then the 4" flange instead.
Any help would be greatly apprecaited.