I recently took on the challenge of adding a shower to my existing downstairs bathroom. The bathroom is inside what used to be the garage so it is far away from any existing vents. After some demo, and finding out that I do not need a permit for the project, the existing pluming looks like this (I hope you can figure out my diagram):
I am pretty sure that the 3x3x1.5 90 degree elbow under the toilet is not up to code. Also, in this configuration we had some issues with the toilet backing up a lot.
As my township uses International Code Council (ICC), I am pretty sure that both wet venting and air admittance valves are allowed. As it would be very hard to run a vent out of the house in this location my plan is to modify the plumbing to look like this:
My questions are these:
Am I good with code?
Do I need to have a second air admittance valve (AAV)?
Could I eliminate either the sink or shower vent?
Would this help alleviate the issues we had with the toilet backing up by getting rid of the 3x3x1.5 90 degree elbow under the toilet, or is there something else I am not considering?