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Thread: Please help with leaking sink? What did we do wrong??

  1. #1

    Default Please help with leaking sink? What did we do wrong??

    I have been dealing with a leaky sink for over 2 weeks now. We had to install a new sink and vanity, complete with drain and facet, basically the works. We determined that the leak is a very slow seepage really, not a lot of water leaking. We think we fixed it and then a day or two later, there will be a small puddle under the cabinet. What is happening is that the new drain that came with the facet setup has 2 holes in the side, like all drains seem to have since I checked and the old sink drains had the same thing. There is a small space between these holes and the sink hole. Some of the water is going into these holes and seeping down around where the black rubber washer meets with the bottom of the sink, where you screw up the plastic cap to hold the washer tight against the bottom of the sink bowl. Anyway, the water sets in this small area then slowly seeps down the side of the pipe. We have, as a last resort put some silicone in the area and I am hoping when I get home it will not have leaked any today, but let me tell you, I am not optimistic. Even if this works, why am i having so much problems. What am I missing here? Please help me,

  2. #2
    Licensed Grump GrumpyPlumber's Avatar
    Join Date
    Jun 2007
    Licensed Grump


    You should have doped the threads first.
    Without dope sometimes tailpieces leak regardless how much you tighten them, then the rubber gasket gets crushed flat from too much torque.
    "The biggest regrets we have in life are the chances we never took."

  3. #3


    I've got the same problem with a sink I did 2 weeks ago. I didn't use anything on the threads of the drain pipe and have a slow drip so I need to take it apart and do as GP says. That's what I get for being too lazy to go out to the car and get the dope. It was for a family member so they got what they paid for


  4. #4
    Homeowner geniescience's Avatar
    Join Date
    Nov 2005
    humid summers hot, humid winters cold


    me too. I had to unscrew that top part and dope it up. The big black washer wasn't any good. I just wish there were generic instructions for all this, put in the packaging with every faucet. It is too much to rely on people who don't do this every day to know which product, where, why, how -- because they only do this once in every little while, or practically never. In my case I felt really dumb since I am signed in here and have been reading everything as it comes for two years running.


  5. #5
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    The two holes you talk about are the overflow. Water is supposed to be there. The ONLY seal in this installation is the fat mack gasket against the bottom of the sink. The threads of the drain body will leak if you do not putty them up. Silicone will work, but will make taking it apart tough later. Some putty or silicone against the bottom of the sink will help with the irregularities sometimes found there.

    You need to take it apart, because you will not likely be successful with gooping anything on from the outside.

  6. #6
    Jack of all trades frenchie's Avatar
    Join Date
    Dec 2006
    Brooklyn, NY and Fire Island, NY


    Please don't get offended if this seems ridiculously basic, it's just that I've seen it a lot:

    Make sure the washer isn't in backwards - the cone-shaped side goes up against the sink, flat side goes down against the washer & nut.

    BTW, guys - I never knew you're supposed to dope those threads. I never have, and I've never had a leak from not doing it... did I just get lucky?
    Master Plumber Mark:

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  7. #7
    Forum Admin, Expert Plumber Terry's Avatar
    Join Date
    Aug 2004
    Bothell, Washington
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    Did you just get lucky?
    They sometimes work without the putty or pipe dope.
    When we install, we dont wait for the leak to develop.
    Right out of the packaging, I smear a little putty on the threads about where the big rubber washer is positioned. That prevents water from finding it's way down the threads.

    You may not know you have a leak unless you do a full test.
    A full test is, filling to the overflow and seeing water pouring down it.
    And then let all of the water down full force.
    That's when you may see water finding it's way down the threads of the drain.


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