How To Get Rid of Drain Flies In Your Bathroom and Kitchen


When I first noticed the tiny black dots floating in the air near my sink, I thought they were fruit flies. Based on this assumption, I threw away all the bananas and put the apples in the fridge. But the mass of tiny black flying dots only increased. And that's when I first learned about drain flies.

These tiny little beasts are too small for us to notice their buzzing. Instead, they float around and get tangled in your eyelashes and nostrils. They tend to congregate near sinks, toilets, floor drains and bathtubs.

“No matter how clean you are, anything that goes down the drain coats it with organic material,” says Eric Braun, an entomologist at Terminix. “Small flies are attracted to this smelly, decaying material, causing a biofilm to build up in your drain, which is the perfect breeding ground for drain fly larvae.”

Once drain flies become established, they can multiply quickly. Therefore, it is good to attack them when you see them for the first time. Here's what to know about drain flies and how to remove them from your home.

About the experts

  • Jonathan Larson is an entomologist, assistant professor and extension specialist at the University of Kentucky. He offers insect expertise for insect problems in the home and urban landscape.
  • Eric Brown is a board-certified entomologist who has served as a technical service manager for Terminix for nearly three decades.
  • Tonya Harris is an award-winning environmental toxin expert, founder of Slightly Greener and author of the Slightly Greener Method, which provides busy moms with simple solutions to reduce toxins. She holds a master's degree in holistic nutrition, multiple certificates in environmental health, and has been featured on numerous national television shows.

What are drain flies?

Drain flies are small flies that live in drains, pipes and standing water. Their larvae (maggots) feed on the slimy growth of these habitats. “They are sometimes called mothflies because they have scale-covered wings and slightly fuzzy antennae, giving them a somewhat moth-like appearance,” Larson says. “If you crush them, you might notice the gray scales of their wings on your hand or whatever you used.”

Fly larvae are difficult to detect in drains, but if you see small flies in your home – often in bathrooms and kitchens – there is a good chance you have them.

“To test [drain flies]“, put a piece of tape over the drain near where you see the small insects,” says Harris. “Drain flies get stuck on the tape as they try to exit the drain, so you can see if there are drain flies in the drain.”

Are drain flies harmful?

Drain flies are not really harmful. It is possible for any fly to transmit disease by passing pathogens from object to object, but Larson says, “Drain flies are not harmful, some might even argue that they are beneficial decomposers that technically help clean the pipes in to clean your home.”

What causes drain flies in the bathroom?

Drain flies often appear in drains that are rarely used, such as a guest bathroom or a basement sink. “This creates a breeding ground,” Larson says. “So the best way to prevent drain flies is to ensure normal use of drains and prevent leaks or clogged drains.”

Run water through your drains and clean them regularly with brushes and boiling water. In some cases, you may even want to remove and scrub the S-trap. Also empty standing water such as mop buckets and trash cans.

“Placing a stopper over drains when used infrequently can also help prevent drain flies from entering the drain in the first place,” says Harris.

How to get rid of drain flies

First, identify which drains are a problem using the tape method mentioned above. Then “clean, clean, clean,” says Braun. But be aware that your usual cleaning chemicals like bleach are no match for these flies. “Most cleaning products don’t work,” he says. “Don’t focus on the adults; You must remove the breeding area. For every adult fly you kill, there could be many more brood in the drain.

To clean the drain, try the following methods:

  • Use a long-handled, stiff-bristled brush to remove the film in the pipe (their food) and destroy maggots and pupae (the life stage between maggots and flies).
  • Try a combination of ½ cup salt, ½ cup baking soda, and 1 cup vinegar, says Harris. In a large bowl, add the salt, then the baking powder and then the vinegar. “Be prepared to quickly pour the combination down the drain,” she says. “As soon as you add the vinegar, it will begin to fizz and fizz slightly.”
  • The next day, pour boiling water down the drain to flush out the remaining debris, larvae and eggs. Repeat this step as necessary.

Larson says once the drain is cleaned, the remaining flies will disappear because their breeding ground is eliminated.

To get rid of any remaining flies, Harris suggests wrapping the lid of a small bowl of apple cider vinegar tightly with plastic wrap. Poke small holes in the plastic for flies to enter and leave it near the drain. “They will be attracted to the sweetness of the apple cider vinegar and will crawl into the bowl, but it will be difficult for them to get out,” she says.

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