Drain flies or sink moths are fuzzy, pesky nuisance insects that live and breed in the moist, organic matter of kitchen and bathroom drains. Only 2- to 5-millimeters long, this grey or tan fly ironically doesn't fly well at all, but rather flits in jerky fits and bouts and can often be spotted resting on the walls surrounding a sink.

Sink moths often show up at sinks that aren't used frequently or are stagnant. They often appear when you get home from a vacation, though they can be just as troublesome in kitchen or bathroom sinks that are used frequently.

While they aren't biting insects, the harmless flies are unsightly and can make people uneasy.

What's more, in small numbers the insects can be considered beneficial since they break down the decomposing wet matter in drains, but they can quickly multiply with a life cycle of up to three weeks and eggs that hatch every 32-48 hours.

How do you know if you've got drain flies?

Easy. As mentioned, you will spot them resting on walls and ceilings near the suspected sink. You can also cover the drain with sticky tape and when the flies try to come out of the drain, they'll stick to the tape. Try to leave the tape overnight or over a weekend to account for 48-hour life cycle variations. If there are flies stuck to the tape, you have drain flies in those pipes. (Note, drain flies are different from fruit flies)

How to get rid of them naturally

To rid your pipes of drain flies without using pesticides or harsh chemicals like bleach or drain cleaner, try these methods:

  1. Use a metal pipe brush and push it through the pipe back and forth as far as it will allow followed by lots of boiling water.
  2. Trap flies by setting a bowl of equal parts sugar, water and white vinegar with a 5-10 drops of liquid dish soap on the counter next to the sink overnight. Flies will be attracted to the fragrant liquid and drown.
  3. Boil a pot of water and pour it down the drain 1-2 times daily for a week.
  4. Pour 1/2 cup of salt, 1/2 cup of baking soda and 1 cup of vinegar down the drain and allow to sit overnight. Follow with a pot of boiling water in the morning.
  5. Pour 1/4 cup of apple cider vinegar into a glass and cover tightly with plastic wrap. Poke holes in the plastic wrap with a fork and place the glass next to the sink. Flies will be attracted to the cider vinegar and work their way inside and drown.
  6. A natural product called Bio-Clean is a nontoxic, environmentally friendly drain cleaner that eats away at organic matter blocking your drain. Once the drain is cleaned, the flies will start to disappear.

Once drain flies are gone, keep sink drains cleaned weekly by pouring 1/2 cup of baking soda down the drain followed by lots of warm water, or pour a cup of white vinegar down the drain weekly and let it sit 30 minutes before flushing with water. Squeeze 1/2 a fresh lemon down the drain for odor control.