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Thread: Unusual Bathroom Vanity Configuration

  1. #1

    Unhappy Unusual Bathroom Vanity Configuration

    Question from a newbie here - what's the best way of routing my drain piping from a vanity basin, the bottom of which is 10 inches above, and 14 inches along wall from 2" waste PVC pipe.

    I think the plumber that did the rough-in was too close to his glue for too long.

  2. #2
    In the Trades Bob NH's Avatar
    Join Date
    Oct 2005
    New Hampshire


    You have a three possible solutions, the third of which will work but will get some pro plumber blasting me here (but I don't mind). You probably didn't get a permit to install the vanity and won't need an inspection.

    1. Get the plumber to fix the piping for free, or pay him to do it right the second time.

    2. Tear it out and do it yourself.

    3. Construct a special P-trap as follows (check fit and dimensions before gluing):

    From the sink, using the tailpiece and pipe, drop down 4 to 6" below the outlet in the wall, and turn toward the wall with a 90.

    At the wall, use a 90 to point diagonally up toward the outlet in the wall.

    At the outlet point, use another 90 to connect the sloping pipe to the wall pipe.

    At some convenient place, reduce the 2" to the size you need for the vanity (1 1/4 or 1 1/2). I would probably do it at the elbow connecting at the wall. Use compression joints at the ends of the trap so you can clean the trap and the downstream pipe.

    Now what you have is a P-trap that consists of the following:
    The tailpiece and extension is the downleg of the trap.
    The first El and the up-angled El at the wall finish the U of the trap.
    The elbow at the wall connection corresponds to the transition from the "vertical" of the trap to the horizontal outlet.

    The total angle change of 270 degrees is exactly the same as a usual P-trap. The only difference is that the leg lengths are a little longer and the "vertical", while providing the necessary vertical distance, is not truly vertical but works perfectly well. The trap will seal and will not siphon because the vent that is in the wall will prevent the pressure from falling below the house pressure, which would be a necessary condition for pulling the water out of the diagonal up leg.

  3. #3
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    Is the problem that the drain runs outside the vanity wall/side?

  4. #4
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default drain

    If the sink and 2" drain pipe are both inside the same cabinet, all you need are the correct fitting(s) to direct the 2" towards the sink drain. DO NOt construct your own trap. It will just make future cleaning more difficult, if not impossible.

  5. #5


    As I am new to this forum, I am really appreciative of all the advice and suggestions, and so quickly at that.

    Cass and hj: the drain line will run completely within the vanity: I was simply looking for a run that would be clean looking and maximize my utilization of cabinet storage space.

    Bob NH: while I think your special P-trap design is spot on, I am somewhat concerned about future clean out problems that hj mentioned. It seems that your design would be fairly easy to clean out though.


  6. #6
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
    Join Date
    Nov 2005
    Central Florida


    Quote Originally Posted by gtfisher
    ...would be clean looking...
    If your vanity is anything like mine, whatever you do will be thoroughly buried within a few months and looks will not be important. I would use a standard trap, though, and the pipe connecting the trap to the stubout won't take up that much space. If you're really worried about looks, build an easily removable false wall for the back of the vanity to hide your plumbing. You could also use that as a hidey-hole for stuff you don't want the casual burglar finding.


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