Mildew smell coming from overflow holes

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by popeye98, Oct 11, 2006.

  1. popeye98

    popeye98 New Member

    Oct 11, 2006
    I have a Kohler pedestal sink in my bathroom and it has 3 overflow holes in the back. I have had the sink for 4 years and all of a sudden (last few months) my husband and I have noticed a very strong mold/mildew odor coming from sink when the water is running. We took it off the wall and cleaned out the pipes and replaced the gasket but a week after we installed it, the odor is back. Now I squirt bleach into the overflow holes which eliminates the odor for about a week, but then it comes back. Any ideas on how to eliminate this odor once a for all? The odor isn't coming from the drain it is coming from the 3 overflow holes. Thanks
  2. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    Your overflow may be somewhat blocked, which is causing water to pool up and create mildew. That is why squirting bleach only temporarily cures the problem. If the blockage is organic, for example, soap scum, hair, etc., you should be able to break it up and flush it out with a huge amount of bleach or a small amount of liquid plumber. If the problem is due to a buildup of mineral deposits, you can try squirting a lot of vinegar down there. I'm not sure what to do if the blockage is caused by a toothpaste cap, etc...
    Last edited: Oct 11, 2006
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  4. Cass

    Cass Plumber

    Nov 12, 2005
    To clean it right the pop up would have to be removed and then you may / should be able to get a bottle brush up into the cavity from the pop-up area and clean it out. You should remove the sink to do this.
  5. Master Plumber Mark

    Master Plumber Mark Master Plumber

    Feb 6, 2005
    Sensitivity trainer.. plumber of mens souls
    indianapolis indiana - land of the free, home of
    bleach and bakeing sode

    try bleach and then bakeing soda down those holes...

    bleach will kill everything dead, dead, dead....

    and the smell should go away.
  6. prashster

    prashster New Member

    Dec 7, 2005
    I had the same prob as you. My builder (won't call him a plumber) put too much plumbers putty around the pop up when setting, and it oozed down into the overflow drain holes.

    Remove the popup so you can see the drain holes. If they're obstructed, remove the drain and re-set it.

    Good luck removing the popup. It's a PITA once the sink's been set (unless yr a pro - me not).

    Alternatively, you might be able to snake it from the overflow holes w some long pipe cleaners.
  7. Verdeboy

    Verdeboy In the Trades

    Jun 12, 2006
    Pipe cleaners is a darn good idea. They also make a very thin bristle brush for very narrow mouth bottles that might even work better. The cleaning surface is somewhat bigger than a pipe cleaner and it is longer.
  8. LoveTLDIYF

    LoveTLDIYF New Member

    Oct 6, 2016
    New York
    I filled the sink to the level of the overflow then poured a gallon of bleach in. Then I pushed the empty bottle into the sink which forced more of the water/bleach into the overflow holes. But then the musty smell became a bleachy one. So I filled the sink up again and this time emptied a box of baking soda by the overflow holes and then pushed the empty bleach bottle into the sink, then poured some white vinegar into the sink and pushed the empty bleach bottle into the mix again. This caused the water/soda mixture in the sink to bubble up and hopefully the reaction helped the cleaning process in the overflow's drainage tube. So far so good. If the smell comes back in a week like yours did I'll take everything apart and then clean it.
  9. Reach4

    Reach4 Well-Known Member

    Sep 25, 2013
    [​IMG] A mustard/ketchup squeeze bottle can be used to squirt bleach. You can cut the tip shorter to increase the diameter if you like.
  10. plumber69

    plumber69 In the Trades

    Jun 20, 2014
    Prince Rupert, British Columbia
    Lots of people don't know you have to line up the po plug hole with the overflow hole
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