Dual Sink Drain Problem

Discussion in 'Remodel Forum & Blog' started by drowe, Nov 13, 2004.

  1. drowe

    drowe New Member

    Messages:
    4
    I am in the middle of a bathroom renovation. I replaced a dual sink vanity with two pedestal sinks. I cut the old PVC waste pipe that fed the two sinks in the old vanity and ran the new pipe so it came out of the wall directly behind each pedestal. After installing new sinks and testing the drain, water is flowing slow and backing up into one of the sinks and leaking out of the slip-joints. What would cause this to happen?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Where was the trap or traps on the old vanity? Do you now have separate traps on each sink? How do they come together into the drain? Do you have pitch on the line?

    Is the wall buttoned up yet,or could you post a picture.?


    Slip joints should not leak even if filled with water. Tighten the connections or replace the gaskets.
  3. drowe

    drowe New Member

    Messages:
    4
    Thanks for the reply.

    Where was the trap or traps on the old vanity?
    There were two traps and were inside the vanity.

    Do you now have separate traps on each sink?
    Yes

    How do they come together into the drain?
    I extended the line and came off the line with a 90 degree T for the first sink and 90 degree elbow at end of the line and came out of the wall to the traps for each sink.

    Do you have pitch on the line?
    Where I hooked into the existing line I expected it to have adequate pitch. This could be a problem though.

    Is the wall buttoned up yet,or could you post a picture.?
    The wall is buttoned up but I have attached a picture. Self extracting zip file attached.


    Slip joints should not leak even if filled with water. Tighten the connections or replace the gaskets. This one I've been fighting with; handtightened, gone over handtightening with a wrench by a half turn, etc. These is new stock. Do the gaskets need to be dressed with anything?

    Thanks

    Dan

    Attached Files:

  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,301
    Location:
    Cave Creek, Arizona
    drain

    Technically you did not install it properly, since there should have been a vent between the two traps. But the way you drew it should work okay, unless the line in the wall is not pitched properly, or there is some other condition inside the wall that your drawing does not show.
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Good picture. Thank you. Do both sinks drain slowly, or only the one on the right? Assuming you did not increase the depth of the trap, is it possible that some construction debris got in the lines? Did the previous sinks drain OK?

    On slip joints, I like the rubber gaskets instead of the nylon ones. They are more forgiving. I use a little vaseline or faucet grease. Nothing is applied to the nylon gaskets.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,301
    Location:
    Cave Creek, Arizona
    rubber

    Vaseline will do the same thing to a rubber gasket as it does to a condum. Eat it up.
  7. LonnythePlumber

    LonnythePlumber Plumber, Contractor, Attorney

    Messages:
    319
    Location:
    Wichita, Kansas
    Neophrene & Dope

    I use the tapered neophrene washers and teflon pipe paste. The rubber ones get old and break and don't fit into the tapered adapter well.
  8. drowe

    drowe New Member

    Messages:
    4
    Thanks all for your tips.

    LonnythePlumber, I'll give the tapered neophrene washers and teflon pipe paste a try.

    Jimbo, both sinks drain slow. When I dump water into the sink on the right water will push up through the trap in the left sink. I don't use this bathroom, so I don't know if it drained slow before or not. But the few times I used it in the past it seemed OK. I did put a level to the pipe before I closed up the wall and had the bubble just to the right of the line; maybe this isn't enough pitch. I did snake line feeding the new work 2-3 feet, so I don't think there's any block that I can tell.

    HJ, why the vent between the two traps?

    Thanks

    drowe
  9. drowe

    drowe New Member

    Messages:
    4
    Problem solved!

    Used the tapered gaskets with silcone paste; worked like a charm. Filled sinks with water and everything held including the papertowel that was 4 feet down the line. Snaked it out and everythings working.

    Thanks gentlemen for your leads.
  10. snugbug47ga

    snugbug47ga New Member

    Messages:
    2
    Location:
    GA
    dual sink connections

    I am trying to add the plumbing to convert a one sink vanity to a two sink vanity , what extra pieces will I need. Also would you have a diagram, since I am not too familiar with plumbing.
  11. Bob's HandyGuy

    Bob's HandyGuy Senior Member

    Messages:
    131
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,301
    Location:
    Cave Creek, Arizona
    vent

    Vent between the two traps because when the farthest one drains it can create a venturi effect and affect the trap seal on the other one.
Similar Threads: Dual Sink
Forum Title Date
Remodel Forum & Blog dual sink connections? Jan 24, 2005
Remodel Forum & Blog Dual saw Nov 14, 2010
Remodel Forum & Blog Leaking dual paned windows Oct 27, 2007
Remodel Forum & Blog Single to double sink vanity - two P Traps with two AAV? Nov 24, 2014
Remodel Forum & Blog Color matching toilets sinks and tubs Aug 25, 2014

Share This Page