I am replacing some 4-inch cast iron vertical and horizontal sewer drain lines. This is in a 3-story, 3-apartment building that I own. The horizontal drain line at the bottom that runs above the basement floor and out to the street will still be 4-inches; I'm just changing it to PVC. But, I want to change the vertical stack and the horizontal toilet lines to the new stack to 3-inch PVC if possible.
Is 3-inch PVC for the vertical stack and the toilet lines that run to the stack okay to use?