Drain flies are small insects that are attracted to clogged pipes and stagnant water. 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 from sewer lines and enter 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.
I’ve dealt with these pesky critters before, and let me tell you, spotting them buzzing around the sink is never fun. The good news? You don’t need harsh chemicals or a professional to tackle them. A bit of know-how and some household items can do the trick. Beyond the methods outlined below, I’ve found that staying consistent with drain maintenance—like running hot water weekly—really keeps these flies at bay. Plus, addressing even minor plumbing issues early can save you from a full-blown infestation.
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.
These little pests thrive in environments where organic matter festers, which is why they love drains. From my own experience, I noticed they often show up in the bathroom sink I rarely use. Scientifically, drain flies are drawn to the biofilm—a slimy layer of bacteria and organic gunk—that forms in moist pipes. According to pest control studies, a single drain can support hundreds of drain fly larvae if left unchecked. To nip this in the bud, I recommend checking all your drains, even the ones you don’t use often, and giving them a quick flush with hot water. It’s a simple habit that disrupts their cozy breeding ground.
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.”
It’s easy to mix these two up since they’re both tiny and annoying, but knowing the difference saves time. I once thought I had fruit flies because I left some bananas out, but the pests kept hovering near the sink—not the fruit bowl. That’s when I realized it was drain flies. A quick tip: if you’re unsure, set out a bowl of vinegar to attract fruit flies. If the flies ignore it and stick to your drains, you’ve got drain flies. Fun fact—fruit flies are more likely to show up in warmer months, while drain flies don’t care about the season as long as there’s moisture.
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.”
Spotting drain flies is pretty straightforward once you know what to look for. I’ve seen them lounging on the bathroom tiles near the shower, especially at night. If you want to confirm an infestation, try this trick I learned: place a piece of clear tape over the drain opening (sticky side down) overnight. By morning, you might catch a few flies stuck to it. Entomologists note that drain flies can lay up to 100 eggs at a time, so if you see even a few, act fast to avoid a bigger problem. Checking drains in less-used areas, like a basement floor drain, is a good starting point.
Why Drain Flies Come Into Homes
Drain flies typically come into the home because they’re attracted to drains and other areas with decaying organic matter, as well as 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.” Don’t forget unused drains. Drain flies often breed in rarely used drains, such as those in guest bathrooms, laundry rooms, or basements. These sinks can collect stagnant water without you realizing it. Run some water through these drains once a week.
Plumbing mishaps are often the culprit, and I’ve seen this firsthand with a poorly installed dishwasher in my old apartment. The water just sat there, creating a perfect drain fly nursery. Experts say that even a small leak or a slow drain can attract these pests, as they only need a tiny amount of standing water to breed. A study from the NPMA suggests that homes with older plumbing systems are more prone to drain fly issues due to worn-out seals and pipes. My advice? Take a quick peek under your sinks for any damp spots or leaks, and run water through unused drains weekly to keep things flowing.
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.
Before diving into the methods, it’s worth noting that consistency is key. I tried tackling a drain fly issue once by just pouring boiling water once, and it barely made a dent. Combining methods and repeating them over a few days is what finally worked. Also, if you’re dealing with a stubborn infestation, you might need to check multiple drains in your home, as these flies can hop from one to another.
How to Get Rid of Drain Flies With Boiling Water
Pouring boiling water down your drains can help remove buildup from the pipes and prevent drain flies from coming back, says Wong. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. Repeat at least once a day for several days to flush out the adult flies and newly hatched larvae in the pipes.
This method is super simple and costs next to nothing, which is why I love it. Boiling water breaks down the slimy biofilm where drain flies lay their eggs. For best results, I’ve found that doing this right before bed, when the drain won’t be used for a while, gives the hot water time to work its magic. Just be careful with boiling water if you have PVC pipes—too much heat can damage them. Check your pipe material first, and if you’re unsure, alternate with hot (not boiling) water to be safe.
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. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. Pour a 1/2 cup of baking soda down the drain. Slowly pour a 1/2 cup of vinegar down the drain. Cover the drain with a drain plug, and let it sit for at least 5 to 10 minutes. Flush the drain again with another pot of boiling water.
This combo is like a science fair volcano for your drain, and it’s surprisingly effective. The fizzing action helps dislodge gunk that drain flies love. I’ve used this method in my kitchen sink, and it’s satisfying to hear that sizzle! A quick cost breakdown: a box of baking soda and a bottle of vinegar cost about $5 total and can last for multiple treatments. One tip—don’t skip covering the drain, as it traps the reaction and makes it more effective. If you don’t have a drain plug, a small plate works just fine.
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 get rid of drain flies. Boil a pot of water and pour it down the drain where you suspect the drain flies are breeding. Follow the product label instructions and apply the drain cleaner.
I’ve tried microbial cleaners when boiling water and vinegar weren’t enough, and they’re a game-changer for tough cases. These cleaners use enzymes or bacteria to eat away at the organic matter, starving the flies out. A decent bottle costs around $10-$20 and lasts for several uses, depending on the size. Pro tip: look for eco-friendly options to avoid harsh chemicals. Also, don’t expect instant results—these cleaners work over a day or two, so keep up with the boiling water in the meantime to speed things up.
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.
Prevention is all about staying one step ahead of these pests. I’ve learned the hard way that letting dishes pile up or ignoring a slow drain is an open invitation for drain flies. Regularly cleaning drains with a microbial cleaner—maybe once a month—has kept my home fly-free. Also, a small investment in drain covers (about $5 for a set) can make a big difference, especially for showers or sinks you don’t use often. According to pest control experts, maintaining good sanitation can reduce household pest issues by up to 80%, so it’s worth the effort to stay on top of it.
