Greetings from eastern NC, again; it has been a while! Advance apologies for the verbosity, and thanks for any help.
I built my 2 story "log mansion" four years ago. With help from you fine folks, and some also from the John Bridge tile guys and gals, I did all my own plumbing, electrical, tile, etc. JAD from Nashua, I see you're still chiming in on both forums?!
Anyway, I must say, that it turned out extremely well! I am very proud of my plumbing and tile work, but...I hadn't planned on three new kids, plus my grown daughter moving back in. So now I'm looking to finish off some rooms in the basement, including a full bath. Ick, I may need to get the whole septic system resized, too, but that's another headache.
I will have to tie in to the 4" PVC building drain, which is overhead, suspended from the 2x10 joists, and goes out to the septic tank (which is higher than the basement floor). I only have one interior 2x4 wall above this basement area to use to get a 2" vent pipe up through to the roof. (The rest of the walls are logs.) The roof above this wall is 2/12, with no attic space. This is in the rear of the house, and the roof here is continuous with that which covers the wrap-around porch.
1) First idea: three fixtures (tub/shower, toilet, and sink) with vents tied together, and then joining the ejector pit vent before going up inside this interior wall to the roof. Is this OK? There seems to be some controversy among you experts on this issue. It will be difficult to line up all the holes to get the vent pipe up. I can't see any other way besides removing the sheet rock floor to ceiling, between two studs, on the inside of the closet above. If I had to, I suppose I could cut a big hole in the roof to get working room, and join two 2" vent pipes together in that narrow angle and come out of the roof with one 3" vent.
2) I want to minimize the concrete excavation, of course. The bathroom will be 13' by anywhere from 6 to 10', and the 13' wall is where the fixtures will be located. But I can arrange them just about any way, as long as I avoid the 2x2' footers for two posts that will be inside this wall. This wall will be either 7 or 13' inside the foundation wall, so I have room behind it. I do have to plumb around the HVAC system in this area. How would you folks suggest to arrange the fixtures to maximize DWV ease and efficiency?
I'm sure I'll have other questions as this moves along, but I need to resolve these issues in my brain and on paper first.