I have a sink which emits an odor from the drain. I checked the p-trap and there was a pretty nasty buildup of black slime in it. I'm cleaning that out, but find it strange that just this one drain has this problem. Another right next to it is fine. The drain with the problem is the highest drain in the house. The vent for these drains seems to be fine, but sometimes I do smell the same odor coming from it. Any ideas on the cause of the slimy buildup in the p-trap?

  • Is this two sinks in the same bathroom? Has the smell always been a problem for this one sink or just this one time? In this statement, "but sometimes I do smell the same odor coming from it. ", you are referring to the adjacent sink? Can you post a picture of the P trap. Apr 8, 2020 at 4:55
  • Is this the first time this P-trap was cleaned? Apr 8, 2020 at 4:56
  • Did you ever get this resolved? If so, please give a check-mark to the answer that helped you the most, or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer.
    – FreeMan
    Dec 4, 2020 at 12:39

1 Answer 1


Being the highest drain might cause a bit more water to be sucked out of the trap causing some odor to get past the remaining water. If it's a bathroom sink, they're prone to gross buildups due to soap scum, toothpaste, shaving cream and whatever. I have a brush from an aquarium that I run down my bathroom drain and trap regularly and it has helped a lot.

  • 1
    True if a double wide sink with 2 drains 1 usually has a horizontal run to the trap so there is more drain line exposed to air , this could also contribute to the smell.
    – Ed Beal
    Mar 10, 2020 at 14:46
  • 1
    Or if, because there are two sinks, that one doesn't get used and the water in the trap evaporates. That happens in our "guest" bathroom tub, I have to remember to run water into it about once every other month or so.
    – JRaef
    Mar 10, 2020 at 21:36

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