So, I am trying to tie into this existing plumbing, and I realize some things are not done right. So the 3in combo shown in the picture is a toilet with a clean out. The toilet is vented by a sanitary tee with a 2 in branch at a 45degree angle to avoid a joist. (is the sanitary tee on it's back ok as a vent?) This 3in line does a couple 1/8 bends to avoid a footing and then ties into a wye at the main. The wye is connected to a 3in sanitary tee which is in a fernco fitting (bushing?) to tie into the main. The vertical is a vent because the toilet used to be connected at this point. On the other branch of the wye we have a tub and vent (off frame camera left) which goes through a combo on it's side with a cleanout and then receives waste from a sink. Here is where the obvious trouble begins. Two sanitary tees on their backs! The first is connected to an old vent and the second is waste from a double sink. I know, I know, a sanitary tee is not allowed on it's back... but... the waste one is right against all of the 3in ABS fittings that tie into the old cast iron and they are all so close that it would all have to be ripped out to get rid of the t. However, the other sanitary tee can be replace by a combo. With the addition I am doing, the combo will be receiving waste from 4 sinks. I would then put a cleanout on the branch of the second sanitary t, so it is kind of like a double cleanout, but with a sanitary tee. Is this ok, or is an inspector going to freak out? Basically, can a sanitary tee be on it's back if the branch is a cleanout?
I have also attached my remodel idea to add a tub and shower on the branch that currently has just a toilet in the existing bath. I would add a horizontal combo where the toilet clean out is and put a new cleanout on the combo. All bends shown are combos and all waste is entering the system through a combo as well.
So, does it sound like this is all going to be to code and Ok, if I make these changes? Sorry it's so much info. Thanks a lot for your replies! Reading this forum has already taught me so much. BTW the picture on the right is looking the same direction as the drawing and the picture on the left is looking from the opposite POV. Oh, and all vents are drawn in Grey.