How to Get Rid of Drain Flies

By Amanda Lutz Updated February 5, 2024

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Drain flies are unique houseguests because they like living in your drains. They can be gross, but they’re easy to get rid of. All you need is patience, a few household supplies, and the willingness to roll up your sleeves.



Fast Facts About Drain Flies

Part of a family known as Psychodidae, drain flies are small, dark-colored insects often found near drains or other sources of standing water. The organic material in these areas provides them with a food source and breeding ground

What Are Drain Flies?

Drain flies belong to a family of about 2,600 species of small flies. Though the scientific name is Psychodidae, people generally call them drain flies, filter flies, sink flies, sewer flies, or sewer gnats. Adults can range in length from one-sixth to one-fifth of an inch.

These insects lay their eggs in the gunk that builds up on the sides of drains, sewage systems, septic tanks, and even compost piles. Drain fly larvae feed on organic matter in the water. 

The Life Cycle of Drain Flies

A single female drain fly can lay a large cluster of eggs in 48 hours. An adult female drain fly lays a single mass of 30 to 100 eggs at once. The entire egg mass is only about three-eighths of an inch long. 

The female prefers to lay eggs in a dark, moist spot where the larvae will have something to eat as soon as they emerge. Thus, drain flies love kitchen sinks, sewers, septic tanks, wet mops, compost piles, birdbaths, and poorly drained lawns. 

About 48 hours after the drain fly eggs are laid, the larvae hatch. For the next eight to 24 days, these larvae will feed on the slime and juice they find in drains or other spots near their homes. After about one to two days as pupae, they will all mature into adult drain flies, which is why you might experience a sudden influx of these pests.

Drain flies breed once, usually just one to two days after they emerge from the pupal stage. Adult drain flies live about two weeks, sometimes more, if provided with enough high-carbohydrate food. Denied nutrition, drain flies die in three to four days. 

What Drain Flies Look Like

With their round heads, separated eyes, and long, hooked proboscises, drain flies look much like fruit flies or other small insects when viewed under a microscope. With the naked eye, however, you can easily tell the difference because of a drain fly’s furry coat. 

Drain flies are weak flyers that can go only short distances, which resemble a moth’s flight pattern. They also have distinctly veined wings and an ovoid shape. Because of their fuzzy appearance and the way they flutter, some people mistake these insects for moths, earning them the nickname moth flies

If you smash a drain fly, it will leave behind a powdery residue from the dense coat of fine hairs on its wings. They can be tan, gray, or black.

What Causes Drain Flies?

If you are coping with a drain fly infestation, it’s likely because there’s something rotten in your pipes—either built-up gunk or standing water.

Drain flies love stagnant water. It gives them a place to lay eggs, survive in the larvae stage, and find sustenance as adults. You’ve probably discovered the insects’ breeding ground if you spot a cluster of adult drain flies gathered around your storm drains, garbage disposal, septic tank, or kitchen sink.

Are Drain Flies Dangerous?

The good news is that drain flies do not lay their eggs on human food nor carry or transmit diseases to humans or pets. A large infestation might trigger a reaction in someone with asthma, but these cases are extremely rare. 

The presence of one or two drain flies probably doesn’t seem like much of a problem, and it wouldn’t be if these insects didn’t multiply so quickly. It only takes one mated pair of drain flies to multiply your population into the hundreds.

What Do Drain Flies Eat?

Drain flies are attracted to decaying organic matter. When you clean your drains and dispose of kitchen waste efficiently, you cut down on a drain fly’s food supply.



How to Tell If You Have Drain Flies

If you have drain flies, you may notice them flying around your bathroom sink or tub, or you may find them in your kitchen sink drain. You could also see tiny black specks on your walls or sink. These are likely the drain fly larvae, which can be tough to eliminate.  

Don’t forget to look in the storm drains and birdbaths outside your home, as well as in your kitchen, laundry room, and bathrooms. Check both sink drains and floor drains. If you aren’t sure which drain is the breeding ground, try covering the openings with plastic wrap or clear tape. If drain flies are stuck to the tape, you’ve found their hiding place.



How to Get Rid of Drain Flies

Once you know you have a drain fly problem, the key to solving it lies in eliminating your unwelcome guests’ breeding grounds.

Clean Your Drains Carefully

Regularly cleaning your drains will kill the larvae and the adult flies. You can opt for a commercial cleaning product—such as a bleach solution or a chemical cleaner—or a do-it-yourself (DIY), environmentally friendly solution.

One such recipe calls for homeowners to pour one cup of white vinegar and a pot full of boiling water down the drain to disinfect it. Be careful if you choose this method because hot water could splash back up on you. 

Baking soda is another effective household drain cleaner. You can mix a half cup of baking soda with a half cup of salt, half cup of lemon juice, or a half cup of vinegar for an environmentally friendly disinfecting option. 

If your drain fly problem persists after a good cleaning, the flies may be living deeper in your pipes. In this case, you may want to invest in a pipe brush. These brushes feature stainless steel bristles attached to the end of a flexible pipe designed especially for home drains. You can scrub out the buildup in your pipes using these tools.

Craft an All-Natural Fly Trap

The most efficient, effective way to get rid of drain flies is to clean and disinfect your drains. However, building a fly trap can add a second line of defense. 

To make an all-natural drain fly trap, fill a bowl with apple cider vinegar and cover it with plastic wrap. Punch small holes in the wrapping. The vinegar’s smell will attract the drain flies, and the wrap will trap them inside the bowl. 

Another option is to mix a few drops of dish soap with a cup of vinegar. The vinegar attracts the flies, and the dish soap makes it impossible for them to stand on the surface, so they drown.

Be aware, however, that these methods only kill the adult drain flies. You must keep a clean, clear drain pipe to deal with the larvae

Consult with Pest Control Professionals

Contact your exterminator immediately if your drain fly issue feels out of control. Drain flies reproduce fast, and the problem could quickly get out of hand. 

Terminix and Orkin are two well-regarded pest control companies that know exactly how to get rid of drain flies for good.



How to Prevent Drain Flies

The best way to prevent drain flies is to clean and disinfect your drains, but you also need to eliminate potential breeding grounds near your home. Drain flies breed outdoors and find their way inside through frayed screens or open vents.

Bug-Proof Your Home

To bug-proof your house, pay attention to where flies enter—sometimes, they fly right in through an open door.

Block all openings in your home that might lead outside, including gaps around doors and windows and cracks in the walls around utility pipes. Seal these areas by caulking or filling any holes with steel wool.

Be sure to cut screens so they rest inside window frames rather than on top of them. Use wire mesh or another netting if necessary. These openings may seem too small for flies, but they are determined little pests.

Maintain Clean Pipes

Make cleaning your pipes part of your regular housekeeping routine. You can pour boiling water down the drain, use a vinegar-and-baking-soda mixture, or use a store-bought product to kill drain flies. Whatever you choose, use it consistently for the best results.

Consult with Your Plumber

Cracks or leaks in your sewage pipes are a great way to attract drain flies and other pests. Ask your plumber to test the integrity of your drain system. 

They will likely run a fluorescent dye test during which they flush dye down your toilet. If that color appears in the sump system or other places it shouldn’t, you have a problem. Your plumber can help repair your system, leaving your home in safer and better condition.



Our Recommendation

To prevent drain flies, regularly clean your drains with homemade or commercial products designed to destroy larvae and buildup in your pipes. Be sure to bug-proof your home, and if the problem flares up again, consult Orkin, Terminix, or another pest control specialist.



Drain Flies FAQ

What are some natural ways to get rid of drain flies?

You can use a homemade, all-natural drain cleaner to help destroy the insects’ larvae inside the pipes. This option offers a green alternative to many commercially produced drain cleaners and can make your kitchen smell fresher than a chemical scent will do. Try this:Start by flushing out your drains and toilets with boiling water. Mix one-half cup of baking soda with one-half cup of lemon juice or one-half cup of salt. (You can also try mixing one cup of vinegar with one-half cup of baking soda in your drain.)Pour the mixture down the drain.Chase it with boiling water.

How do I make my own drain fly trap?

To make your own drain fly trap, you can use a mixture of apple cider vinegar and plastic wrap to attract and then trap drain flies. Pour one-quarter to one-half cup of apple cider vinegar into a bowl. Cover it with plastic wrap, then use a fork to poke holes in the wrap. Set the dish next to your sink. The drain flies will not be able to escape and will drown in the vinegar.An alternative option is to put a few drops of dish soap in a bowl of apple cider vinegar. The dish soap keeps the flies from using surface tension to stay above the liquid, causing them to sink into the vinegar.

How do I prevent drain flies?

Clean drain pipes help prevent drain flies. As part of your home care routine, scour your drains with a homemade or commercial cleaner and possibly a pipe brush.Also, check your screens for holes that drain flies could enter. Cover any vents or pipes that open to the outside. Finally, discuss any concerns about drain flies with your exterminator and your plumber.

How do I permanently get rid of drain flies?

The most efficient and effective way to get rid of drain flies for good is to call in your pest control professional. They can identify the breeding site, remove the larvae, and destroy the adult flies, leaving none behind to recreate the problem.

How We Chose the Top Pest Control Companies

Our pest control research process starts with analyzing customer reviews on third-party websites such as the Better Business Bureau (BBB), Trustpilot, and Google Reviews. We then do a deep dive into each company’s website, service plans, and available cost information. We also secret shop the companies we review, reach out to representatives, and request quotes.

From there, we compile the information we’ve gathered and compare each company using our in-depth pest control methodology and review criteria. This process uses a series of factors that are important to our readers, and we score each company depending on how well they perform in each factor. For instance, companies that offer more guarantees for their service earned more points than others, and pest control plans with a larger range of covered pests earned more points than ones with fewer.

After analyzing dozens of residential and commercial pest control businesses through this process, we were able to determine the best pest control companies on the market.