# Do I have Drain Flies? And what to do?? **URL:** \ **Category:** Factual Questions\ **Created:** [January 20, 2020, 2:42pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702 "2020-01-20T14:42:43Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![salinqmind](https://avatars.discourse-cdn.com/v4/letter/s/3ec8ea/32.png) [@salinqmind](https://boards.straightdope.com/u/salinqmind)\ **Post date:** [January 20, 2020, 2:42pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/1 "2020-01-20T14:42:43Z")
Tiny black flying things in my bathroom sink, I am assuming from research they are drain flies. They’re in only one sink, in a half bath where we just wash our Hands with liquid soap. Eww. Will boiling water eliminate them or is there something else I should do? ---
**Author:** ![Paintcharge](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/paintcharge/32/7946_2.png) [@Paintcharge](https://boards.straightdope.com/u/Paintcharge)\ **Post date:** [January 20, 2020, 2:50pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/2 "2020-01-20T14:50:06Z")
I’ve used bleach on them with pretty good results. Just poured some down the drain and let it sit. ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [January 20, 2020, 3:05pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/3 "2020-01-20T15:05:19Z")
Bleach is the default solution. The flies lay their eggs in the grease that tends to coat the pipes. So a couple of treatments may be necessary. If that doesn’t help, or if your septic system doesn’t like large doses of bleach, try replacing the pipes above the U-trap under the sink. And treat the overflow passage. That is the hole near the top of the sink that prevents the sink from overflowing. Good luck. ---
**Author:** ![doreen](https://avatars.discourse-cdn.com/v4/letter/d/858c86/32.png) [@doreen](https://boards.straightdope.com/u/doreen)\ **Post date:** [January 20, 2020, 3:33pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/4 "2020-01-20T15:33:08Z")
> [@rbroome](#): > > Bleach is the default solution. > The flies lay their eggs in the grease that tends to coat the pipes. So a couple of treatments may be necessary. If that doesn’t help, or if your septic system doesn’t like large doses of bleach, try replacing the pipes above the U-trap under the sink. And treat the overflow passage. That is the hole near the top of the sink that prevents the sink from overflowing. > Good luck. Bleach didn’t work for me. I used a foaming pipe cleaner ( liquid plumber or Drano, don’t remember which) . But I also discovered that although I had flies in the bathroom , they were breeding in the kitchen sink. Not really sure how they got from one to the other , but once I treated the kitchen sink, no more lies in the bathroom. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [January 20, 2020, 4:11pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/5 "2020-01-20T16:11:10Z")
The other big fly problem, fungus flies around plants, falls to Yellow bowls with water and a drop of soap in them. They’ll drown by the hundreds. Yellow seems to be their very favourite colour. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [January 20, 2020, 4:32pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/6 "2020-01-20T16:32:46Z")
Two flies are sitting on the edge of a bowl. First fly: What’s your favorite color? Second fly: Blue. … No, yel-- aaaaah!!! ---
**Author:** ![salinqmind](https://avatars.discourse-cdn.com/v4/letter/s/3ec8ea/32.png) [@salinqmind](https://boards.straightdope.com/u/salinqmind)\ **Post date:** [January 20, 2020, 5:15pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/7 "2020-01-20T17:15:39Z")
> [@doreen](#): > > Bleach didn’t work for me. I used a foaming pipe cleaner ( liquid plumber or Drano, don’t remember which) . But I also discovered that although I had flies in the bathroom , they were breeding in the kitchen sink. Not really sure how they got from one to the other , but once I treated the kitchen sink, no more lies in the bathroom. I was surprised to see then in the half-bath sink, I KNOW my kitchen drain is a teaming cesspool of horror! Since we had the garbage disposal taken out, it has been just disgusting, with a little mesh thing to catch the bigger bits. So I will try the boiling water and bleach in the kitchen sink, too. Thanks for the replies. I swear, vermin is everywhere! Mice in my car, flies in my sink, what next? ---
**Author:** ![Manduck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/manduck/32/256_2.png) [@Manduck](https://boards.straightdope.com/u/Manduck)\ **Post date:** [January 20, 2020, 9:08pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/8 "2020-01-20T21:08:21Z")
I had success using baking soda chased by vinegar, followed a few hours later by boiling water. It did take a few repeat applications. ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [January 21, 2020, 12:52pm UTC](https://boards.straightdope.com/t/do-i-have-drain-flies-and-what-to-do/846702/9 "2020-01-21T12:52:59Z")
I had them in the passage between the toilet tank and bowl. They developed some sort of crusty substance which ended up blocking off some of the holes. After trying some remedies, I ended up replacing the toilet which needed it anyway, it was the cheapest toilet I think was ever made. I would be surprised if the builder spent all of $25 on it.