How to Get Rid of Drain Flies

Drain flies, often called moth flies, lurk about your bathroom, shower, or kitchen. At first you may suspect a moth has snuck in the house through an open door or window. However, no matter how many times you shoo or splat the moth looking creature, it is quickly replaced. Carefully observing the creature, you’ll realize that it doesn’t flit and fly about as a moth would, and it seems to struggle when it does attempt to fly. All of its limited movements seem to concentrate around the drain in the floor, shower, or the kitchen sink. Rather than a moth, you are probably experiencing a drain fly infestation.

All About Drain Flies

Drain flies are a pesky non-biting filth fly. Filth flies are flies that live and breed in organic matter such as manure, animal carcasses, garbage, and drain sludge. Filth flies are divided into large filth flies and small filth flies. The larger of the filth flies are the ones you must protect your cheeseburger from at a BBQ or swat away at the horse stable. Large filth flies such as the house fly, the blow fly, or stable flies have stout bodies and short legs. Small filth flies, like the drain fly, phorid fly, and fruit flies have small bodies. These small filth flies prefer to breed in the rotting organic material that builds up in a drain, garbage can, dumpster, or septic tanks. In this article, the recurring theme is to get rid of drain flies, you must eliminate the breeding site. Adult drain flies lay their eggs in accumulations of gunk and grime. To truly get rid of drain flies, you must locate, thoroughly clean, and keep clean the area where the drain flies are laying eggs.

Identifying Drain Flies

To the untrained eye, drain flies look like moths, but they behave quite differently. Drain flies are approximately 1/8” in length. Drain flies have a mottled appearance as they are covered with short dense hairs giving them a fuzzy moth-like appearance. Their coloring ranges from grey and brown to almost black, but most commonly they are greyish. They are most commonly seen resting on walls or structures near the breeding ground. When resting, they fold their wings roof-like over their body. When they do attempt to fly, it more closely resembles a hopping motion, running, or a short burst of flight travelling only a foot or two at a time.

Life Cycle of Drain Flies

Drain flies are one of the few insects that can live out their entire life cycle in our homes and businesses. Because our homes can present the perfect environment for the rearing of their young, drain flies can successfully reproduce indoors.

Drain flies mature to adult hood using complete metamorphosis. From the time the egg is laid, the drain fly can emerge as an adult in as few as 21 days, but in the unbearably hot southern summers, this time frame may be shorter. The female drain fly lays her eggs on areas filled with moist organic matter. She is very careful to ensure the eggs will not dry out. She commonly attaches the eggs to the gunk and grime clinging to the sides of drains. Usually, she lays 20-40 eggs at a time. These eggs are transparent in color and less than 1mm in diameter. On average the eggs hatch in about 2 days, and the worm-like larvae emerge.

When closely inspected drain fly larvae are actually fairly well developed and intricate. At initial glance, they look like a simple worm, but they are actually quite detailed. Drain fly larvae, which are technically maggots since they are fly larvae, are about 3/8” in length, do not have legs, but are white or cream colored throughout the middle section of its body. However, its head and rear end are a darker shade of brown. The drain fly larvae has 11 distinct body sections and also includes well developed mouthparts and a breathing siphon. This wriggling larvae is covered with short tufts of hair.

The larval phase is the longest life stage for the drain fly. During this larval stage, the immature drain fly feeds upon the grime into which it hatched. The film of gunk that builds up in the drain is necessary for this species to mature to adult hood. The larvae feed on bacteria, fungi, algae, and other micro-organisms in the slime that develops in drains, sewage treatment beds, and standing water. Drain flies can reproduce outdoors as well, but absent certain circumstances outdoors they don’t make pests of themselves. In the great outdoors, female drain flies may deposit her eggs in wet soil that is ultra-rich in organic matter. Outdoors, drain fly larvae usually stay close to the soil’s surface. However, in specialized circumstances, such as a sewage filter bed, drain fly larvae may be found deeper because of the high concentration of trapped oxygen.

Drain fly larvae are quite durable. They can withstand extreme temperatures and periods of low oxygen. While submerged in muck, they breathe by extending their tube-like tails to the surface. However, they also have the ability to trap air bubbles and live off their siphon for an extended period of time. This survival mechanism is the reason that drain fly larvae are hard to kill. They are hardy little creatures who can withstand attacks of bleach, ammonia, and hydrogen peroxide.

The drain fly larval phase usually lasts between 8 – 15 days depending upon the ambient temperature. Then, they pupate, or enter a cocoon like enclosure. The pupae are yellow to brown and tubular in shape. Extending from one end of the “cocoon” are what appear to be 2 Shrek like horns. These are called respiratory trumpets. Drain flies remain wrapped up in the cocoon for 1 -2 days depending upon the temperature, then emerge from their gunk as adults.

Despite their name, adult drain flies are poor fliers. They are usually found resting near the drain from which they emerged. Indoors, adult drain flies only live a few days, 3 or 4 days maximum. However, outdoors where food sources such as nectar is available, adult drain flies can live for about a week. The rapid life cycle of the drain fly ensures that you will never gain control of a drain fly infestation by reaching for the bug spray under the sink and killing the adults. Less than 10% of the population are adults. She has probably already set the reproductive process in motion and laid her eggs. The real battle against drain flies is won in the nursery where the eggs, larvae, and pupae are found.

How Do Drain Flies Get in My House?

Because of their filth breeding nature, one could assume that drain flies emerge from the sewer, making their way up your pipes and into your home. Thankfully, that is typically not the case. Drain flies get into your home or restaurant by open doors, holes in screens, and other small openings. Just like the fruit flies that buzz around your over-ripe bananas, small, inconspicuous drain flies slip indoors unbeknown to us at the time. Once inside, drain flies desperately need to find a suitable location to lay eggs. Unless they find a location where their progeny can thrive, this lone fly will likely die off quickly and you’d never even know it was there.

Where Drain Flies Live

Drain flies require near constant moisture, hence they are most often found indoors in kitchens and bathrooms.

Indoors, drain fly infestations may occur in or near:

• Toilets (particularly seldom used toilets)
• Sink and bathtub/shower drains
• Floor drains in commercial buildings and basements
• Condensate lines for icemakers and HVAC units
• Loose floor tiles where water and organic debris can accumulate
• Garbage cans with wet gunk on the sides on the bottom
• Kitchen compost container

Outdoors, drain fly infestations may occur in or near:

• Damaged or faulty septic lines
• Shady areas where water lines or a hose leaks
• Areas of extreme moisture where mold or fungus is present
• Underneath or beside outdoor HVAC units
• Clogged gutters
• Sewage treatment plants
• Potted plants with standing water
• Outdoor compost areas

Of course, nature has a knack for finding ways to survive. The above list is by no means exhaustive. Essentially, drain flies require moisture with a bit of filth mixed in. If there is a slow leak under the refrigerator and food bits get pushed under the fridge, drain flies can find it and lay eggs. If your laundry machine drips a bit of dirty wash water every load, drain flies can exploit that. To eliminate a drain fly infestation, you must find the breeding location. This can be a tricky proposition when the nursery is elusive and out of the ordinary.

How to Get Rid of Drain Flies in a Restaurant

Drain flies is a term sometimes used collectively to refer to all small flies that can breed in drains such as true drain flies, phorid flies, and fruit flies. In this article we will focus on true drain flies. With their moth-like appearance, drain flies may not inspire immediate concern in a commercial kitchen like roaches or rats, but do not ignore their presence. As a restaurant, hotel, food truck, or other kitchen run for commercial purposes, the general public is relying upon your vigilance to remain healthy. As you know from your training and experience in your kitchen, you have a high duty to the public to ensure good safety practices and cleanliness.

Drain flies, sometimes called a moth fly, are small flies that are hairy or fuzzy like a moth. These nuisance flies are usually found resting on walls or ceilings, but their mere presence indicates a breeding site is nearby. Drain fly breeding sites are problematic in your commercial kitchen because it shows things are not being cleaned as thoroughly as they should be.

Drain flies lay their eggs in the slime and gunk that accumulates in drains and other wet areas. Anywhere that holds water can be the drain fly breeding ground. Moist, slimy, decaying organic matter and gelatinous film that forms over the water, is ideal for drain flies to lay their eggs. Drain flies really like breeding in sewage. Sink and floor drains in restaurants are the most common source of the drain fly larvae, but do not overlook drain pans under the refrigerator, around or inside of garbage containers, wet sewers or leaky toilets, condensate lines for ice makers, and even under a leaking washing machine. Drain flies have been known to propagate in a water and organic matter than accumulates under a broken or loose tile.

Do Drain Flies Bite or Spread Disease?

Adult drain flies do not bite humans. Indoors, adults only live for a few days and generally stay close to the breeding ground where they developed. Since they do not have the ability to bite humans, they are not known vectors of blood borne diseases, such as those spread by mosquitos and ticks. However, they live in filth and sewage. It is possible that they spread bacteria and germs throughout the kitchen or bathroom. Drain flies can spread diseases related to contact with fecal matter such as E.coli. For example, if drain flies are breeding in sewage they may pick up E.coli bacteria and then land on a food prep surface or a soda fountain spreading the bacteria to food and beverages. They are not strong fliers, so they spend most of their time resting on walls or other surfaces. If they emerged from sewage or trash, they likely carry with them particles of the sewage or trash. As they hop around and walk across your counters, they can spread the bacteria on surfaces you commonly touch, your toothbrush, or your kitchen utensils, infecting you with more than a touch of an upset stomach.

In those who are susceptible, large accumulations of drain flies have triggered allergic reactions and asthmas attacks. Drain fly infestations can quickly escalate, particularly if you cannot find the breeding grounds. Especially, if you are prone to allergies and asthma, deal with drain flies promptly to prevent an exploding population.

Signs of a Drain Fly Infestation

In residential homes, the most common sign of a drain fly infestation is a moth-like insect resting on the bathroom wall. It is seemingly benign, until every day more and more “moths” are hanging out in your bathroom or kitchen. You may see these moths hovering near the drain you have been meaning to clear for the past month.

Small worm-like larvae around drains are also a key sign. Broken floor/shower tiles or missing grout that allow “gunk” to build up behind the tiles are also favorite breeding sites for drain flies. Often, drain flies are present when you come home from an extended vacation or may be able to establish themselves in a bathroom that is rarely used. When water remains stagnant in a drain, the bacteria and funk that drain fly larvae feed on is allowed to fester and grow. It is a good idea to periodically run the water in guest bathrooms and other seldom used drains.

Drain flies may also act as a proverbial canary in the coal mine. If after inspecting and thoroughly cleaning your drains, you cannot get a handle on a drain fly infestation, you need to continue to dig. Drain flies may indicate a leaky water pipe behind a wall or under the sink. If drain flies preemptively warn you of this potential flood and expensive damage before it manifests, then consider the drain flies a blessing in disguise.

Bleach or Ammonia for Drain Flies

It is a reasonable assumption that bleach, ammonia, or other caustic cleaning chemicals down the drain would kill the larvae feasting inside. However, this is not the case. Above where we discussed the drain fly life cycle I mentioned that these larvae are resilient and hardy. This is where their extraordinary abilities come into play. Drain fly larvae can essentially hold their breath while these chemicals are in the drain then safely proceed with their lives once the danger has passed. Bleach does nothing to remove the gunky buildup that drain fly larvae call home, therefore does not help to solve this pest problem.

Ammonia is another substance that many assume will kill drain fly larvae. Again, it does not. Drain fly larvae can resist this harsh chemical and live to fight another day. Combining bleach and ammonia is not only ineffective against drain flies, it is a dangerous combination. Bleach and ammonia combine to form chloramine vapors which can be deadly to humans. Do not ever put these 2 chemicals together down your drain in order to battle drain flies. It will not work and it is extremely dangerous.

Furthermore, bleach is caustic and may damage old pipes. Pouring straight bleach down the drain will cause corrosion on metal pipes, but it is not great for PVC pipes either. Undiluted bleach down the drain can cause the sealant around the pipe connections to break down and cause leaks within the plumbing system. Even if bleach and ammonia helped with the drain fly infestation, it is not worth risking life and your entire plumbing system to rid yourself of these pesky drain dwellers.

How to Get Rid of Drain Flies Naturally

Everyone is looking for natural alternatives to pest control problems. We encourage natural pest control methods that are effective and environmentally sound. Drain flies are one infestation that we can safely say, there is a natural alternative to pesticides. The most natural of all home-remedies is a bit of elbow grease. In fact, the most effective drain fly treatment is to remove the breeding ground. Without a suitable environment to lay their eggs, drain flies will not survive indoors. Whether the drain flies are in the shower or sink drain, in a pool of liquid filth at the bottom of the trash can, or under the refrigerator, you clean the source, you get rid of the drain flies.

When considering how to clean the drain, steam can take some of the manual labor out of the process. If you have an active infestation of drain flies, do not rely on steam to completely resolve the problem. However, a hearty stream of steam will kill bacteria and push through the bulk of the gunk and grime clinging to the sides of the pipes. Regularly blasting the drains with steam will keep them clean and prevent drain flies from using them as a nursery for their young. The only drawback to steam is it quickly cools down and may not penetrate very far. Small steamers for getting wrinkles out of your clothes probably will not reach all the breeding sites in the pipes. Commercial grade steamers cost about $500-$1000 and do a much better job. They are also often available for rent at local hardware stores. For commercial buildings, there are even companies that specialize in bringing in large truck mounted steamers to thoroughly clean every inch of drain pipes.

Drain fly infestations may involve a bit of detective work. They must have moisture and organic buildup, but sometimes moisture is found in unexpected places. When drain flies were found in a hospital operating room, experts sourced the infestation back through the ceiling tiles then into a cellar which had recently flooded. The flood waters had risen sufficiently to cover the duct work and electrical wires, and due to the moisture intrusion, this was believed to be the source of the drain flies many floors above. As always, you must find the breeding ground (moisture source) and remedy that situation before you can hope to gain control over the drain fly infestation.

Drain Fly Pest Control Treatments

Drain fly treatments should be a regular part of the pest control procedure for commercial kitchens and restaurants. Commercial kitchens are particularly vulnerable to drain flies due to the vast amount of food being processed and potential variations in cleaning procedures and habits. Floor drains, commonly found in restaurants and commercial kitchens often take the brunt of the refuse from a hard day’s work. These floor drains have a tendency to accumulate debris and gunk, thus harboring drain flies. Cleaning and maintaining all drains in a restaurant quarterly should always be part of the master pest control plan.

To get rid of drain flies, you must find the breeding location. Whether it be a drain, a plumbing leak behind the wall, gunk in a trash can, or any other moist location with organic matter, the drain flies will not go away until this location is thoroughly cleaned. Thoroughly cleaning a trash can or under the refrigerator, while not fun, is easy in that it is accessible and not incorporated from many intersecting pieces. Thoroughly cleaning a drain can be difficult if you lack plumbing or basic home repair abilities.

Scrub the Drain Clean

Often it is easy to know which drain is infested with drain flies. You will notice them hovering, hopping, and flitting about near that drain. You may even see them flying down into the drain or fresh newly adulting drain flies emerging from the drain. If you have trouble narrowing down the drain which is the source of your fly infestation, consider covering each drain with duct tape or an upside down paper bowl coated with 3M spray adhesive. After a few days, check the duct tape. If you have adult drain flies attached to the tape, you have drain fly eggs, larvae, and pupae in this particular drain. However, you should not assume that the drain flies are being supported solely by this drain. It is possible to have multiple breeding locations in your location. Scrubbing one drain clean while leaving others infested will frustratingly delay solving this pesky issue. Optimal results in pest control always rely upon a thorough inspection. Set yourself up for success by solidly knowing where to spend your time and attention. Once you know which areas are harboring drain flies, you can readily know which drain to vigorously attack with your cleaning energies.

To thoroughly and completely remove the gunk and grime that harbors drain flies, you’ll have to take the drain apart and scrub it to remove the accumulation of organic matter. Scrubbing around the rim of the drain with an old toothbrush will not do the job. Purchase a long-handled metal pipe brush specifically for this job. This flexible yet sturdy brush has stiff strong bristles that can dislodge organic debris and blockages from the depths of the pipe. This action will remove the eggs, larvae, and pupae along with leaving no suitable place for adults to return to lay eggs. When battling drain flies, there is really no substitute for this dirty job. With severe infestations, the expertise of pest management professionals may be coupled with the expertise of plumbers. If a severe cleaning of the offending drain does not rid your home or business of drain flies, continue the hunt/inspection. There may be a breeding location hiding behind a wall or even outside of a window.

Chemical Drain Cleaners for Drain Flies

As you educate yourself on drain flies and how to get rid of them, you will come across a lot of bad information. Many resources encourage you to simply pour drain cleaner down the drain and magically your drain flies will disappear. Chemical drain cleaners are rarely effective to completely solve a drain fly problem. You will spend a lot of time and money which you literally pour down the drain. Drain fly larvae are resilient enough to live through a Draino attack and continue to mature to adulthood. The gunk that remains after a drain cleaning treatment will be plentiful enough to continue the breeding process. In addition, keep in mind that anything you put down the drain eventually ends up in waterways. At Nextgen Pest Solutions, our protocols always seek effective solutions to pest control problems while keeping our environmental impact to a minimum. The manual drain cleaning method is a more appropriate and a more effective way to clean an actively infested drain.

However, once a drain is clean, there are products that can safely keep it clean. Intrinsic to its purpose, organic matter will always make its way down a drain. Add in some hair to retain these bits of food and you are concocting a slurry ripe for a drain fly infestation. Once a drain is thoroughly clean, it is worth the effort to keep it clean. Rather than harsh drain cleaners, regularly applying probiotic bacterial drain cleaner will prevent the accumulation within the drain. This product can be applied to clean drains at night and has a thick viscous consistency and a fresh citrus scent. Microbes within this product actually consume the organic material which is the breeding ground for the drain flies.

Gravity is the biggest hinderance to the application of this product. Although many of these products have a thick consistency which clings to the sides of the drain, they still drip down the drain quicker than we would like. Often part of a drain fly pest control program involves creating a foam with this product. By transforming this microbial gel into a foam, it stays in place longer allowing it to be more effective. This product can be purchased in a few different formulations. It is most commonly available as the thick clingy liquid, but can also be purchased in a thinner liquid, an aerosol can which expels a foam, and even concentrated tabs for specific purposes.

Especially in commercial kitchens, the regular pest control program should pay special attention to the drains and keeping them clean. As part of a pest prevention plan, regularly foaming the drains will help to keep them free of organic debris and pests. Your pest management professional uses specialized equipment to transform this enzyme cleaner into a foam which continues to eat away at the grime long after a liquid has dripped down. When a health department inspection is on the line, it is always better to prevent a pest infestation than battle an established infestation.

Insecticides for Drain Flies

The probiotic bacterial drain cleaner discussed above is not considered a traditional insecticide. It does nothing to kill or hurt the insects themselves; the goal of this product is to keep the drain clean and free of the organic material food-source where drain flies can lay eggs and the larvae can thrive. It is a natural product which contains naturally occurring enzymes. These enzymes eat the filth trapped in the drain which in turn reduces the available food and habitat for drain flies. Like all animal species, drain flies require food, water, and shelter or habitat to survive and multiply. This natural product is an effective way to remove their habitat, thus effectively gaining control of their presence.

Most insecticides are not labelled for use in a drain. In fact, it is a violation of federal law to use about 99.9% of insecticides in the drain. When battling drain flies, never reach under your sink and shoot a puff from the aerosol can you bought from the grocery store. It won’t work against the drain flies and it is likely illegal. Any time you consider using a pesticide, read the label on the product carefully, and only apply the product in places that have been specifically approved.

One class of insecticide that is EPA approved for use in drains is called an insect growth regulator, or IGR. Insect growth regulators do not necessarily kill the insect, like the roach you spray in your bathroom at night. They work differently. IGRs are low-toxicity products that break the life cycle of the insect causing the populations to diminish and eventually die out. IGRs cause a deformation within the insect which prevents them from maturing to adulthood. IGR products must be carefully applied to areas of drain fly infestation, but your pest management professional can legally and safely apply them to a troublesome drain.

Nextgen Pest Solutions – Drain Flies

Drain flies are a pest which may act as an indicator of another problem. In restaurants and other commercial establishments drain flies hovering on the walls and near drains are unacceptable and certainly not the image you wish to project to your customers. In addition, other pest species such as roaches and other fly species may propagate because of the accumulation of grime. 

Solving a drain fly problem may require some detective and inspection skills and a bit of elbow grease. Nextgen Pest Solutions can provide additional support and expertise in solving a drain fly infestation. At Nextgen Pest Solutions, our Integrative Pest Management, IPM, approach to solving difficult pest problems such as drain flies, is an effective and scientifically backed protocol. Our technicians are continually updated with the latest research and methodologies to ensure your 100% satisfaction.