Lavatory drain size mismatch

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by steve42, Apr 11, 2011.

  1. steve42

    steve42 New Member

    I didn't notice an introductions area on the site, so I'll just say that I was directed here by bronsonb from the John Bridge - Tile Your World forum.

    My wife and I are in the process of remodeling our front bath, and when I got ready to reinstall our existing pedestal sink, I realized a) the new p-trap assembly I purchased was not going to fit and b) the old p-trap assembly must have made it into the waste collection when they came to get the stuff that was torn out.

    The pipe/nipple exiting the wall is approx. 1-7/8" OD. If I recall correctly, on the old assembly, the outlet pipe slid inside this nipple and then a slip nut tightened onto the nipple to lock it in place. I could be wrong on this, as it has been a few weeks since the sink was removed. In any event, I'm at a standstill on the sink until I figure out what I need. I could rely on the associates at HD or Lowes, but I'd rather go in armed with some knowledge.

    Thanks for your assistance.

    Last edited: Apr 11, 2011
  2. Terry

    Terry Administrator Staff Member

    Bothell, Washington
    The pipe from the wall is a 1-1/2" pipe.
    The tail piece on the lav drain is 1-/4"
    You would normally get a standard 1-1/2" p-trap and use a 1-1/2" x 1-1/4" reducing slip joint washer on the tail piece.
    That should do it.
  3. steve42

    steve42 New Member


    The pipe from the wall is larger than 1-1/2". At the mouth of the pipe, the OD is 1-13/16" threaded - once the threads stop, the overall OD of the pipe is about 1-7/8". I would estimate that the ID is about 1-11/16" or so. I can't attach a photo right now because I am using my work computer, but I took a picture of it with a tape measure across it so I would have it.

  4. hj

    hj Moderator & Master Plumber Staff Member

    Cave Creek, Arizona

    That IS the size of 1 1/2" pipe. You need a 1 1/2" tubular trap, (it will have a 1 1/2x1 1/4 slip washer with it to connect to your sink drain).
  5. SacCity

    SacCity In the Trades

    Sacramento, CA
    Yes everything is as it should be. As you noted the Pipes are given with a nominal size, none of the dimensions measured on the pipe are likely to be the nominal diminsion.
    For example on copper pipe the Outside diameter of the pipe is definded as nominal size plus 1/8" so a half inch pipe will have a 5/8" outside diamter etc....

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