Why Are Flies Coming From My Drains?
Those small, fuzzy moth-like flies near sinks and floor drains are Psychodidae — drain flies. They lay eggs in the gelatinous film coating the inside of the drain throat, just below the strainer. Spraying the surface does nothing because the larvae are protected inside the film.
How to confirm the source
Tape clear plastic over the drain overnight. If flies appear stuck to the underside in the morning, that drain is the breeding site.
The fix is mechanical plus chemical
Scrub the drain throat with a long-bristle brush, then apply a foaming enzymatic cleanser that expands to fill the pipe and contact the film 360 degrees around. Repeat weekly for three weeks to break the breeding cycle.
Why bleach fails
Bleach runs straight down without contacting the film. Foam clings. That's the difference.
Frequently asked questions
- Are drain flies dangerous?
- Not directly, but they indicate buildup that will eventually clog the line.
- How long until they're gone?
- Two to three weeks of weekly foam treatment breaks the cycle.
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