• Size: The adult drain fly (or moth fly) is one-sixteenth to one-quarter of an inch long. Drain fly larvae are about one-quarter of an inch long with skinny bodies and no legs.
  • Color: Adult drain flies have a dark gray body and lighter-colored wings. Fine hairs on their bodies and wings give drain flies a fuzzy, moth-like appearance (hence why they’re often called “moth flies”).
  • Behavior: Drain flies are most active at night. They are weak flyers that make short hopping flights of a few feet when they are disturbed. Drain flies rest on surfaces with their wings held over their back like a roof. You’ll usually find a drain fly close to its breeding ground.


These flies live and breed in moist areas with a buildup of organic debris.
Indoors, you may find drain flies in:

  • Sink and bathtub/shower drains
  • Infrequently used toilets
  • Floor drains in basements
  • Drain pans under the refrigerator
  • Loose ceramic tiles where water collects

Outdoors, you may see drain flies in or near:

  • Air-conditioner drains
  • Faulty septic lines
  • Areas where rain collects, especially shaded areas
  • Areas where algae or mold grow on the soil or foundation

Drain fly larvae are rarely seen because they live in drains or other hidden places.

Tips for Control

You can make homemade traps to locate infested drains. Coat the inside of a cup or jar with petroleum jelly or vegetable oil. Put the inverted jar over the drain opening. When a drain fly leaves the drain, it will stick to your trap. Leave your traps in place for 24 hours before checking for adult drain flies. This will be a primary area to attack.

Clean toilets, sinks, drain pipes and traps with a stiff wire brush. Use industrial drain cleaner to remove the slimy organic debris from your drains. If you have a septic system, use an approved septic treatment. Be sure to read the product label carefully to be certain the cleaner is safe to use with your system.

Use an enzymatic drain cleaner regularly to prevent the accumulation of organic slime that attracts drain flies.

Do not pour insecticide down your drain. In residential homes, pesticides are often unnecessary to control drain flies. Thoroughly cleaning your drains, thus removing the food sources, will most likely eliminate your drain fly problem.

Contact Terminix® to allow one of our pest control specialists to inspect your home and evaluate your propensity for a drain fly infestation.