Hi, I posted a while back about doing a basement bathroom and am about to start the project. I was wondering if there is a rule or code that requires the 4"PVC stack to extend all the way to the joists in the basement before going with a reducing bushing to take off with the vent, OR, can I save some money by reducing to vent just above my waste line which comes in from the side of the stack and enters about three feet below the joists (yes I am only saving about 3 feet of 4" PVC but I am trying to see if I can recycle some of my old stack rather than buying another 10 feet, only to use a foot or two)? Thanks in advance.
Regards,
Steve

If the 4" stack has nothing draining into it and is dry to the roof yoiu can reduce to 2"PVC at least 6" over the flood rim of the lavatory. Good luck. Tom