University of Maryland Extension

Drain Flies

close up drain fly

Drain flies are found primarily in rooms or areas where there are drains: such as kitchens, basements near floor drains, etc. Drain flies are small, 1/16 to 1/4 inch long, delicate and fuzzy. They are pale brownish gray to black. The larvae live in the gelatinous film or slime in drains and traps. They feed on algae, bacteria, and fungi in the slime. They may also breed in areas of sewer leaks, back-ups, dirty garbage cans, saucers under potted plants, clogged storm drains, and in condensate pans under refrigerators and air conditioners. Adult flies may live up to 2 weeks and total development time from egg to adult may take 7 to 28 days. Flies emerge daily once an infestation is underway.


To control drain flies clean traps and drains mechanically or with an over-the-counter drain cleaner followed by hot water. Clean or eliminate breeding sites. 

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