I've got a two story house with a separate apartment on the upper level. I am in the process of remodeling my unit and have discovered a shattered cast iron elbow in the drain system for the apartment upstairs. I plan to replace the all of the cast iron (vents will remain cast with the new pvc tying in) with pvc down to the basement. Is 3" large enough for a toilet, bathroom sink, kitchen sink and bathtub? The existing setup has the bathtub drain going into one side of the closet bend and kitchen and bathroom sinks tying in to the opposite side. What size should I use for these two pipes? This drain system will service the upstairs apartment only as the bath in my unit is part of an addition which has its own stack with all of my drains tied in.
