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Thread: No-overflow sink draining slow

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  1. #1

    Default No-overflow sink draining slow

    Back in January I told my husband I needed a pantry. A whole lot of money later we have a new powder room, a new laundry/mudroom and a big island in the kitchen, as well as the pantry. We've passed Electrical final inspection and I thought the plumbing final would also be no problem. Unfortunately, the inspector said our powder room sink is draining too slowly. Its all new plumbing so we know its not a clog.

    The Kohler sink is one without an overflow. The drain thingy in the sink is just a strainer grid - it can't be used to keep water in this sink. The tailpiece came with this drain thingy (from Westbrass). I'm assuming its for no overflow sinks since it can't be closed.

    My contractor thinks the problem is the vacuum since there isn't an overflow. The plumber said the same. Kohler tech support said I should have used a Kohler one and its not their problem.

    I'm wondering if anyone else has run into this problem with the no-overflow sinks or vessel sinks (and how did you solve it?) Any ideas are so very appreciated!!


  2. #2
    Plumber plumber1's Avatar
    Join Date
    Aug 2005


    Those Kohler drains with the grid like strainer have always been noted to drain poorly. A drain fitting with a "+" like strainer would let water out better. They come with a rubber stopper. Probably hard to find too.

  3. #3
    Plumber/Gasfitter dubldare's Avatar
    Join Date
    Sep 2005


    It's actually caused by an air bubble under the grid strainer.

    I have found some success in drilling through a few of the holes at an angle.
    --Customers of plumbers: Never be afraid to ask for proof of licensure of the plumber servicing your equipment. A licensed plumber will be proud to show you his personal license.--

  4. #4


    Also, tell your contractor that overflows have little to do with the speed of draining.

    A slow draining sink is caused either by an obstruction in the drain or the vent. He's probably thinking the overflow functions as the vent, which is not the case. The vent is positioned downstream of the trap and delivers air to the drain to prevent a vaccuum (a strong one will suck the trap dry, a weak one will cause slow draining). Displacement air is also supplied by the sink drain hole, which delivers way more air than the puny little overflow can.

    The only purpose of the overflow hole is to prevent yr sink from, er, overflowing if it fills too much. The overflow tube delivers water back to the drain - not air. It's not necessary, only a nice-to-have.
    (important note: I'm not a pro)

  5. #5


    Thanks for you help. I see bubbles form around the holes of the grid and if I take my finger and rub the grid it flows better until the bubbles form again so I can see it seems to be a bubble problem.

    Is there any retro-fit I can do to help this (it seems too thin to drill holes at an angle with this grid and its the oil-rubbed bronze material so finish would be ruined)?

    How can they sell these kind of drain thingys to us unknowlegible (clueless on plumbing) homeowners if they don't work so well?

    Thanks again,

  6. #6


    I'm about to buy a grid drain and wonder if the original poster or anyone else can share what ultimately succeeded?

    In particular, I'm wondering if this "tear drop" shaped drain works better (MT749):

    For various reasons, we'd rather not have a pop-up. So thanks for any info on what ended up working!


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