I am going to frame a wall in the laundry room so all the plumbing is out of sight. I want to tie in a washing machine drain and a utility sink drain into the main stack. The stack is currently a 3" copper line that I will be changing over to PVC. Should I use a sanitary t or a wye when connecting to the vertical main stack? Can I use the main as a vent or should I use an air admittance valve? The washing machine will be to the left of the stack and the utility sink to the right. Thanks in advance for any help I receive.