I installed a new faucet and drain pipe assembly. I found that there's a small hole at the bottom of the sink (underneath). Water is coming out of it. When I pull up the stopper (so the water collects inside the sink), there's no leakage. But as soon as open the stopper or open the faucet, water is start dripping through this hole.

Anyone knows why is it here, why is it leaking, and how could I fix it? There didn't seem to have a cover or "plug" for it previously.

Thank you.

enter image description here

  • 3
    Do you still have the old drain pipe assembly? This looks like it's tied into the overflow system for the sink. your old drain pipe might have covered it up.
    – JACK
    Jun 5, 2020 at 23:43
  • You know, you might be right. We have 2.5 baths and all of them are the same (original construction). The other ones have a big rubber gasket under the sink, which might be covering up that hole. This new one is not as wide so this hole is visible. I am SO glad "standards" are exist and they are keep changing it every so often...
    – pentool
    Jun 6, 2020 at 0:25

1 Answer 1


This looks like it's tied into the overflow system for the sink. Your old drain pipe might have covered it up. If the old gasket will fit on the new drain pipe you could just reuse it or get a duplicate gasket from your plumbing supply store. I would hesitate to just plug up the hole because you never know when your plug would fail and you'd have a big leak. It could also compromise your overflow protection. You could also just put the old drain pipe back on the sink if you can't get a new exact match.

  • Yes, it was covered up with a bigger rubber seal. The old piping was 20 years old and was metal. This new one is plastic and nut and seal is smaller. I got me some putty and plugged up the hole for now. If it doesn't work, I might cover it with some silicon as well. The old piping was rusty and the inside (stopper) rot away and broke so I could not put it back. Thanks for our advice and tip!
    – pentool
    Jun 6, 2020 at 2:35

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