Hi, I'm contemplating fixing my existing bathroom drains and vent since I'm already going to be messing around with the plumbing to add a second bathroom. I'd like to see if there are any issues with what I'm thinking about doing...
This shows the plumbing in the house currently (the upstairs bath isn't plumbed yet, but that's the plan)
Now, the downstairs plumbing does not vent very well, and I think it's because of the hack plumbing job that was done previously. The toilet is about 26ft from the vent pipe, and it doesn't have the best flushing power. The drains for the tub and lav take convoluted paths (some uphill!) before they connect to the drain line. I'd like to add an AAV at the existing first floor lav, and connect the three fixtures in a similar fashion to the plan for the upstairs bath.
The red dashed lines show roughly what I'm planning on doing.
And here is a sketch of the plumbing plans for the new 2nd floor bathroom. The plumbing inspector helped me figure out how to plumb the second floor bath.
Do you see any problems with what I've sketched here?
The line sizes are as follows:
3" for WC drains, and vent
2" for shower/tub drains
1.5" for lavs and kitchen sink
I would take your plans to the local codes office and visit with them about the changes you have planned.
Also check with them to see if AAV's are allowed. Some code jurisdictions don't allow AAV's. Just adding AAV's to a plumbing system is just bad venting. AAV's are allowed in my code when NO other means of venting is possible.