what are the measurements for framing a wall off the centers of each pipe in my basement? i also have a large round plastic cover in the concrete floor and was wondering what that was for? if i could have finished measurements off the drywall id appreciate it. i have a 4 inch pipe, and it looks like 2 2 inch pipes. 1 of the 2 inch pipes has a square in the floor around it with dirt surrounding it like the concrete wasnt poured around it totally.