Ok, I am thinking about doing the plumbing for an addition myself and would very much appreciate your help in laying it out. It is a small addition, just 150 sq. ft. spread out over three floors (so, approximately 50 sq. ft. per floor. In the rear of the house (where the addition will be) the basement is entirely above grade. This will be heavy in plumbing as the 2nd level of the addition will have a half bath and the 3rd level a full bath.
My plan right now is to run a 3" stack up one corner of the addition where both baths will tie into. This "stack" (not sure if this is the right term in this application) will tie into the house's main 3" cast iron stack (which currently services 1 full bath). In general, does this work? In order to get this where it needs to be it will require 3 long sweep 90's, is that overly problematic?
Can I run the 3" stack right up and out the roof and use it to vent the various fixtures? I know each fixture needs its own vent, but can I tie it all up together in the attic and have just one protrusion through the roof?
So, can I check dwv sizes?
Toilet - 3" drain, 2" vent
Lavatory - 1.5" drain, 1.5" vent
Tub/shower - 2" drain, 1.5" vent
Am I right on these?