I am building a house where the living area is on a second story level over a garage. There are two bathrooms and they are both upstairs. The living area floor is precast concrete and I am getting ready to do my plumbing rough in. The underground plumbing is a 4" PVC pipe that presently comes out of the garage slab and sticks up a few feet. I am wondering what size toilet drain pipe and size of the other drains for showers and sinks. I need to rent a core drill and bits. I don't know if you drill an exact size opening in the concrete or if you oversize it a bit. Any advice is greatly appreciated.