, Hello. The attached picture shows how a 2 inch drain line from my laundry area turns down 16 inches or so down into the wall cavity and into the wye connection on the 3 inch stack. I am hoping to remove the wall and enclose the stack within a column. I only want to enclose the 3 inch stack and pressure lines to keep the column as small around as possible. Therefore, I would like the washer drain line to enter the stack in the ceiling area, not in the wall cavity. The vent pipe on the far right is only for the kitchen sink and it will be replace with an air admittance valve. That will leave only the 3 inch stack and the pressure lines to be enclosed within a column. I am asking if the existing 3 inch 90 deg elbow from the toilet could be replaced with a double 90 elbow so that the 2 inch washing machine line drains into one side (with a bushing), and the toilet drains into the other opposite side of that proposed double. Or is there some other suggestion? Thanks