3 Easy Ways to Get Rid of Drain Flies—and Prevent Them From Coming Back

If you see small, hairy insects hovering around your drains, it's possible you have a drain fly infestation. These pests are attracted to damp, humid areas and typically originate in sewer lines, entering homes through drain pipes. While these pests generally aren't harmful to humans, an infestation can quickly become a nuisance. Luckily, there are a few easy DIY methods you can use to get rid of drain flies, as well as prevent future infestations.

What Are Drain Flies?

Drain flies (Psychoda spp.) are very small flies that are under a quarter-inch (3 to 6 millimeters) in length and have gray to black coloring. They have a fuzzy appearance with hairy bodies and wings, which give the insect a moth-like appearance, says Jim Fredericks, board-certified entomologist and senior vice president of public affairs at the National Pest Management Association (NPMA).

Drain flies are usually caused by slow or clogged pipes, which lead to a buildup of moisture and organic debris. They typically breed in damp, humid areas such as sinks, showers, bathtubs, floor drains, and laundry rooms, says Timothy Wong, technical director at MMPC.

Drain Flies vs. Fruit Flies

The main thing that sets drain flies apart from fruit flies is what they're attracted to. "Fruit flies are usually found in kitchens because they're attracted to the smell of ripe fruit, rotting vegetables, and fermented products like vinegar and wine," says Wong. "Drain flies require high amounts of moisture and prefer to feed on bacteria, fungi, and organic matter that builds up inside drains."

How to Know if You Have Drain Flies

You can identify drain flies by their appearance and behavior. "If you see small, furry-winged flies around drains, sinks, or moist areas in your home, it's likely that you have a drain fly infestation," says Wong. Additionally, drain flies are weak fliers, so indoors, they are typically seen crawling or hopping on walls or surfaces. "During the day, they typically rest on vertical surfaces near drain openings indoors and in shaded areas outside," says Fredericks. "Their greatest activity is in the evening when they can be seen flying or hovering above drain openings indoors or sewage areas outside."

Why Drain Flies Come Into Homes

Drain flies typically enter the home because they're attracted to drains and other areas with decaying organic matter, as well as to slow or stagnant water. "It's common to see drain flies because of plumbing issues," says Wong. "One of the most common causes is improper connection of appliances, particularly dishwashers, when the drain line is connected to the wrong side of the kitchen sink P-trap."

How to Get Rid of Drain Flies

The best way to get rid of drain flies is to eliminate their food source and breeding grounds, which you can do a few different ways.

How to Get Rid of Drain Flies With Boiling Water

Pouring boiling water down your drains can help remove buildup in the pipes and prevent drain flies from returning, says Wong.

1. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. 
2. Repeat at least once a day for several days to flush out the adult flies and newly hatched larvae in the pipes. 
   

How to Get Rid of Drain Flies With Baking Soda

If boiling water alone doesn't do the trick, use baking soda and vinegar. "The baking soda and vinegar react together to help break down the organic matter clogging the drain," says Wong.

1. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. 
2. Pour a 1/2 cup of baking soda down the drain.
3. Slowly pour a 1/2 cup of vinegar down the drain.
4. Cover the drain with a drain plug and let it sit for 5 to 10 minutes.
5. Flush the drain again with another pot of boiling water.

How to Get Rid of Drain Flies With a Microbial Drain Cleaner

Microbial drain cleaner, a solution that kills bacteria and breaks down organic matter in drains, is another effective way to eliminate drain flies.

1. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. 
2. Follow the product label instructions and apply the drain cleaner.
   

How to Prevent Drain Flies

The best way to prevent drain flies from coming back—or avoid getting them in the first place—is through vigilant sanitation and simple home updates.

• Review all recent water-related appliance installations.
• Fix any plumbing leaks and ensure that drains are not clogged.
• Remove organic debris and food particles from drains.
• Clean drains regularly by using enzymatic or microbial cleaners.
• Keep sink and shower drains covered when not in use.
• Dispose of trash daily.
• Check that all windows and doors are properly screened.
• Discard any decaying food.
• Dispose of trash daily.