09/13/2026
https://www.facebook.com/share/19LCmTJkA4/?mibextid=wwXIfr
You bleached the drain, gave it a week, and the little flies came right back.
Here is what you are up against: the pipe under your sink is coated in a gelatinous mat of bacteria, hair, soap scum, and grease, roughly 1/8 inch thick, clinging to the wall above the standing water. Moth fly larvae live their entire lives in that film, and the two species you will find in American homes are Clogmia albipunctata and Psychoda alternata. Pour in a cup of bleach and gravity pulls it past that wall in about one second. Boiling water cools on the way down and slides off just the same. Because the film is not water soluble, liquid runs right over the top of it and the larvae inside stay dry.
The way they breathe finishes the job. Each larva has a siphon at its tail that it pokes up through the surface of the film into open air, so flooding the drain drowns nothing. They also shrug off low oxygen and big temperature swings, holding a spot most insects could not last an hour in. Their family, Psychodidae, includes the sand flies that carry leishmaniasis in the tropics, and dried Psychoda debris is a documented trigger for occupational asthma in sewage workers. A few flies over your sink are not dangerous, but this history explains why the group thrives in filth.
To pin down the guilty drain, you need one night and a strip of clear packing tape. Lay it sticky side down over the opening at bedtime, leaving a small gap so the drain can still breathe, then count what is stuck in the morning. Test every drain the same way: the shower, the laundry standpipe, and the sink overflow hole too.
The real answer is a brush, not a bottle. Push a stiff drain brush 6 to 8 inches down the pipe and scrub until the film peels off in strings, then add a bacterial enzyme drain gel to digest whatever you missed over the following nights. Since egg to adult runs 8 to 24 days depending on pipe warmth and the adults survive about 2 weeks past that, keep this up once a week for 3 weeks straight and they will finally stop coming back. [BNDK0]