3 inch waste line going straite to the toilet down stream 8 ft is my lav which acts as vent for toilet before I turn up through the floor for the lav can I put a san tee on and go and catch a bathtub and a seprate shower or am I overloading the two inch vent? Or can I go down strem from the lav cut in a 3x2 wye and run over to the tub and shower and revent them ? Nc code is vent 8 ft from weir of trap.