i have a situation nearly identical to that posted by "mamabirrd" on 4/19/08 and was very impressed with the info provided by "lazypup" about venting. the 'side view' of my system has a 4" vent stack up-stream servicing a toilet on the 1st floor and a washer discharging into a laundry tub in the basement teed into the same stack. the 4" then goes under the floor for about a 40' run close to where i want to break in and add a w/c, lav. & shower and continues on out to the street. as i understood lazypup, he said no vents were required for any of the new fixtures. i'm hoping to get this confirmed or rebutted with another recommendation. all the diy books show vents all over the place, yet what lazypup says makes perfect sense to me. thanks in advance.