I just moved apartments, and when I went to the bathroom, there was a lingering smell of mold. When I looked at the bathroom sink, I could see the stopper had some white mold on it. So I took the stopper out to clean it and scrub the drain with a pipe cleaner.

But when I removed the stopper, I noticed there were two gaps on either side of the pipe that were gummed up with gunk. It took me part of a day and a lot of scrubbing to get the gaps clean. I have no idea what purpose these openings serve though. In the gap, there's rubber that looks shaped like a shock boot.


What are these gaps for? And if anyone has advice for keeping them clear, you'd save future me some headache.


Here are some photos taken after cleaning out the gaps.

Sink view from above

Gap on right side of sink

Gap on left side of sink

View under the sink

  • Tighten the nut on the lever; it's leaking. Not too much though or it won't move anymore. With the sink full go at it with a plunger (pull as hard as you push); might get some of the gunk out of the trap and help with the smell.
    – Mazura
    Jun 30, 2022 at 20:52
  • 1
    Odd: It looks like those holes were cut after-market.
    – Hot Licks
    Jun 30, 2022 at 23:46

1 Answer 1


Bathroom sinks typically have an overflow hole which routes the water into the drain instead of overflowing your sink in the event that your stopper is engaged and the water is left running.

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Per your edit:

It's possible the manufacturer forgot to drill the overflow holes or it's cheaper to just use the same drain for all sink styles.

I wouldn't be surprised if your landlord installed a bargain-bin sink with a defect.

Per the new picture under the sink:

It looks like an overflow was not planned at all in your sink basin. So the manufacturer/plumber/installer did simply use a drain designed for an overflow and leakage is mitigated by the rubber collar/boot.

  • Thanks, MonkeyZeus. This sink doesn't have an overflow hole, but could it be that the rubber is covering what would have been where the overflow hole drained?
    – JRagone
    Jun 30, 2022 at 15:32
  • @JRagone I must have missed that detail in your pictures. Post a picture of the underside of your sink while you're at it. It's possible the manufacturer forgot to drill the overflow holes or it's cheaper to just use the same drain for all sink styles. Do those holes leak anywhere?
    – MonkeyZeus
    Jun 30, 2022 at 15:36
  • It doesn't look like the holes leak anywhere, but I posted a pic of the underside of the sink. It's a little cramped under there, so lmk if you need a better view.
    – JRagone
    Jun 30, 2022 at 15:46
  • I fully agree with monkeyzeus + but that looks like a molded sink and the overflow was not added. (They are a headache on many basins) the holes are drilled a channel is glued to the side that leads to the pipe ring at the base of the sink to drain. I have seen quite a few of these fail so you may be lucky you don’t have an overflow.
    – Ed Beal
    Jun 30, 2022 at 16:36
  • @JRagone See my newest edit.
    – MonkeyZeus
    Jun 30, 2022 at 16:53

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