Original Mess

I am trying to move a double sink vanity to the wall on the left where we closed in the closet door. This 1977 floor plan didn't make a lot of sense to us so we are doing a full remodel of the bathroom and closet in the MB. I have been researching all day and the one thing I can not figure out is if I can extend the drain that is already in the wall leading to the 3" waste line. I believe I can, and if so, do I need to add a vent to the extension or will the one that will be 6+ feet away be fine? I do not want to bust up concrete and move the waste line over as this would be too costly at the moment. Any help would be extremely appreciated!

What I know so far
Drain must be at 1/4" slope
My vent pipe is 1 1/2" and the sink drains are being upgraded to 2" diameter
My waste line is 2"

What I think:
Can't move drains more than 3'6" from 1 1/2" vent (If this is correct, I will need to add a vent but do I also need to add waste line under the slab? Or is it fine to keep it in line the way it is?)

Edit: Added a diagram for critiquing. I am pretty sure that some of it is incorrect and I need to get it finished ASAP. We are moving in soon and I want it to work properly and be up to code.

Positioning on wall


  • have you actually reviewed your post after you submitted it?
    – jsotola
    Mar 30, 2020 at 7:17
  • Hello, and welcome to Home Improvement. Would you edit your post to fix your images? And, you should probably take our tour so you'll know you'll know the details of contributing here. Mar 30, 2020 at 12:27
  • The waste line should be fine with a 1/4” slope, the vent I thought was 5’ or 6’ I would check your local rules and if air admittance valves are allowed you are so close I would not want to punch a new vent. But AAV’s are not code compliant everywhere.
    – Ed Beal
    Mar 30, 2020 at 16:39


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