I have a 12' wall that has a washing machine, shower, (toilet) and a lav along it. Am I able to drain the 2" washer standpipe, a 2" shower drain and a 2" single lav drain into the same 2" drain pipe that would run directly under these 3 fixtures prior to it emptying into the 3" toilet drain? The drain for these 3 fixtures run parallel to iin its own joist bay which is adjacent to the joist bay where the toilet drain runs. They would combine near tbe end of the run whete head space is noongrt a concern. Each drain would have its own dry vent.