Drain Flies Not Coming From Drain

How to Identify Where Drains Flies Are Coming From

Drain flies can also be referred to as sewer, moth, or sink flies. They live and breed in moist places and feed on the organic matter found in drains, contaminated soil, sewer lines, or septic tanks.

You may also find them around wet mops and buckets, basement sump pits, compost piles, birdbaths, and wet areas around barns. Any place with shallow, stagnant water is a prime breeding ground.

Though not harmful since they do not bite, sting, or transmit human disease, they can be quite a nuisance in large numbers. Also, they can spread bacteria from the filth they live in onto surfaces they land on, contaminating the surface. Massive infestations can also clog pipes, leading to costly damage.

For these reasons, if you notice the presence of drain flies in your home, you need to get rid of them using DIY homemade solutions, store-bought products, or the services of a professional exterminator.

What are drain flies?

Drain flies are tiny, fuzzy gnats that measure about 1.5 to 5 mm long. They have six legs, a pair of wings, and antennae, and their body color varies from tan to gray to brown.

picture of a drain fly from above

You can also identify them by the unique pattern of veins on their wings and their erratic flying patterns. They are poor fliers and tend to hop or fly short distances when disturbed.

Also known as moth flies, drain flies tend to leave behind a powdery substance when crushed.

Female drain flies lay 30 to 100 eggs at a time in the scummy buildup in drain pipes or stagnant water. These eggs hatch in 32-48 hours, so it’s easy for things to spiral out of control. A drain fly’s complete life cycle lasts 1-2 weeks.

pipes with buildup inside them

Drain fly larvae are about 4 to 10 mm long when fully mature. They are wormlike in appearance. The larvae do not have legs or eyes and are gray with darker ends, where a breathing tube extends out of the film on the water surface to obtain air.

What causes drain flies?

These flies thrive in moist, humid environments. They breed in standing or stagnant shallow water, making drains the perfect breeding grounds. Drain flies feed on the organic matter inside the pipes and will come into the house through access points such as the kitchen sink and shower drains.

dirty drain open and being cleaned

In some instances, the breeding grounds can be outside your home. Potential locations include compost piles, animal waste, storm drains with standing water, birdbaths, barns, and wet areas around garbage.

You will notice more drain flies when you return home from vacation or after you have gone away for an extended period. This is mainly because no water has been moving through your pipes. Hence, the water inside your drains has been sitting around. Some drain flies tend to disappear once you get your home up and running again.

How do you identify a drain fly infestation?

The presence of adult drain flies in your home is the first indication that you may be dealing with an infestation. You can spot these flies resting on the walls and ceilings of an infested area or hovering inside a sink.

Since they are not good at flying, they tend to be very near their breeding ground. So, the starting point would be to check the nearby drain pipes for infestations using the following methods:

Duct tape test: Cover all the pipes with sticky tape. As flies try to come out of the drain, they will get stuck on the tape, giving proof of the source of the infestation. Do this in the evening when the drains are not in use.

Also, do not cover the drains entirely, as it may prevent the flies from attempting to come out. Leave the tape overnight or for a weekend if possible. If you find the flies stuck on the tape, you have found the breeding ground.

If not, repeat the test for 4 more nights to account for differences in the breeding cycle.

Check for larvae: Open your drain cover, remove any gunk you see, and search for tiny larvae.

drain fly larva

These have long, tube-like bodies. However, this is not a fool proof method because, in many instances, the larvae may be originating deeper within your pipes.

How to get rid of drain flies

The best way to get rid of drain flies is by eliminating their breeding grounds. Get rid of organic matter in your drains using DIY homemade solutions or store-bought products.

man cleaning drain with brush

DIY solutions

Once you identify the source of the drain flies, you can try these DIY solutions to clean your pipes and get rid of organic buildup and adult flies.

  • Vinegar and baking soda: Pour ½ cup of baking soda down the drain, then slowly pour in a cup of vinegar. Allow this to sit for a while to loosen the buildup, then rinse with a pot of boiling water.
  • Boiling water: Pour hot water down the drain once or twice a day to dislodge and remove larvae and eggs. Ensure that the water is not so hot that it will damage your pipes.
  • Pipe brush: Use a pipe brush to scrub and clean the drains and dislodge organic matter. Then rinse with boiling water.
  • Homemade traps: To eliminate adult flies, mix equal parts sugar, water, and white vinegar in a jar. Add 5-10 drops of liquid dish soap and leave the mixture next to the sink or shower drain overnight. You can also use an apple cider vinegar fly trap. Adult drain flies can also be killed by spraying them with dish soap and warm water.

However, treating a drain fly infestation using DIY homemade solutions can be a lengthy and time-consuming process. If you don’t manage to eliminate the eggs and larvae, you will continue to have a recurring drain fly problem. In this case, it is time to try store-bought products.

Store-bought products

These include traditional drain cleaners (such as Drano and Bio-Clean), chemical sprays, repellents, and enzyme cleaners. Common products include:

ProductHow it works 
American Bio-Systems Drain GelIncorporates microorganisms, with biological support ingredients and essential growth factors, that degrade organic materials. It also prevents the production of foul odors.
Natural Armor Fruit Fly and Drain Fly KillerThis drain gel treatment is made of natural ingredients with no toxic substances. It is ideal for bars, bathrooms, homes, hotels, kitchens, and restaurants.
Green Gobbler Fruit Fly KillerThis formula traps and kills fruit flies, drain flies, and other sewer flies. It is a non-caustic and non-corrosive formula that is safe for pipes and septic systems.
Gentrol Insect Growth Repellent (IGR) AerosolControls flies by interfering with their normal development. It disrupts the life cycle by killing flies at the pupal stage and provides 120 days of pest control.
Green Gobbler Enzyme Drain CleanerControls odor and breaks down grease, paper, fat, and oil to get rid of buildup and scum while still being safe for septic systems.
InVade BioDrain GelInstead of harsh chemicals, it contains microbes, which work by dissolving scum and organic buildup in drains and pipes. It is also safe for septic systems.
DF5000 Drain CleanerUses a blend of enzymes and bacterial cultures to break down organic buildup in pipes. It is a nonacid, non-caustic bacterial product that rapidly biodegrades organic matter.
Forid Drain Gel CleanerContains microbial grease degraders that dissolve scum and buildup inside pipes.

Note: Carefully read the instructions before using any of these products.

Popular drain fly products

person shopping online

How do you prevent drain flies?

Since they feed and breed on organic matter, the first step is regularly maintaining and cleaning your drains. The second is to ensure you don’t have stagnant water either sitting in your pipes or caused by leaking pipes. Third, seal all possible drain fly entryways to prevent adult flies from accessing your home.

Final thoughts

If you have unsuccessfully tried to get rid of the flies using the above methods, it may be time to seek professional help.

Professional exterminators may not be as helpful in this scenario as you may think, since the issue might be due to broken sewer pipes, or other plumping issues. There is still some ongoing departed whether your first call should be to a plumber or exterminator.


Can you kill drain flies with bleach?

While bleach may kill drain fly larvae, it comes with certain risks, including creating toxic fumes when the bleach mixes with other substances. Also, pouring full strength bleach down your drains may permanently damage your septic tank (if you have one). Bleach flows down too quickly and may not be effective in getting rid of thick buildup or drain fly eggs and larvae. An exception to this would be if your RV blackwater tanks were infested.

Why do drain flies keep coming back?

Drain flies may keep coming back due to poorly executed or ignored mechanical cleaning; failure to eliminate all breeding grounds, surviving eggs, and larvae; and failure to conduct regular cleaning and maintenance of the drain pipes. Adult flies can continue to get in from outside, so seal all possible entry points. In some cases, a broken sewer line beneath the basement floor can be the cause of infestation. Killing adults will not solve the issue, although you might get a moral boost.

Will mothballs keep drain flies away?

Mothballs contain naphthalene, which is toxic and can kill drain flies that emerge from their breeding ground. Concentrate the mothball vapor by covering drainage outlets or pipes with a clear container and the mothballs, trapping the flies inside the drain. Keep the drain covered for at least two weeks to eliminate the flies. However, if you don’t remove the buildup in the pipes, the problem may recur since you haven’t gotten rid of the breeding ground. Using mothballs to kill drains flies is NOT recommended.

How long does it take to eliminate drain flies?

With persistent treatment, you can manage most drain fly infestations in under a week. Sometimes, you may have a significant issue throughout your pipes. In that case, you may need to consult a pest control professional to get to the root of the problem.

Last update on 2024-07-22 / Affiliate links / Images from Amazon Product Advertising API