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Thread: Drain question for adding second bathroom sink

  1. #1
    DIY Junior Member Carsonic's Avatar
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    Default Drain question for adding second bathroom sink

    I am adding a lav sink about 4 feet to the right of the existing one. I've built a little half wall to run the plumbing through so it goes behind my new cabinets. I need to know if I should put the tee in the vertical tailpipe section of the existing sink so I can plumb it similar to my 2 kitchen sinks only with a farther distance (my research so far indicates "probably not" ) or if I should put it in the main.

    All I have seen are diagrams of drains halfway between the 2 sinks, so I'm concerned that there are issues with my asymmetrical setup that will cause me trouble. I am going from standard sinks to vessel sinks and raising the level of the countertop, if that makes a difference.

    Thanks for the help!

    (I live in GA, btw.)
    Last edited by Carsonic; 10-20-2010 at 02:57 PM. Reason: added details for clarity

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Four feet is too long for one trap...the trap arm would collect crud and be open to the air and eventually generate some nasty smells. Depending on where the vent is, you might need some fancy footwork if it is essentially an island (you can't go up with the vent). You'll probably need a loop vent. A quick search will show you some possible ways to do this. A diagram of what you have and what you want might make it easier to comment.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Junior Member Carsonic's Avatar
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    Thanks Jim, here's a picture of what I'm doing.

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    DIY Senior Member dlarrivee's Avatar
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    You're going to have to open the wall up.

  5. #5
    DIY Junior Member Carsonic's Avatar
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    Quote Originally Posted by dlarrivee View Post
    You're going to have to open the wall up.
    Okay, why's that?

  6. #6
    Plumber jimbo's Avatar
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    Quote Originally Posted by Carsonic View Post
    Okay, why's that?

    Because you need to add another sanitary tee on the vertical stack. The distance between the two sinks would result in the "TRAP ARM" length exceeding code, and in general you cannot combine two traps into one trap arm either, so you need a new connection.

    I will say that based on what I have read on the forums over the years, the strictness that inspectors feel about this exact issue varies a lot. You might just want to add.

    If you "get away with it" that long arm will be prone to gunking up. Try to put a good slope down from the far sink.

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