Drain Flies (Sewer Flies)

Drain Flies (Sewer Flies): Everything You Need to Know

A common nuisance, drain flies are small, pesky insects that can be found year-round due to ideal living conditions in our homes. In this post, we’ll cover everything you need to know about drain flies, commonly called sewer flies — including what they look like, if they’re harmful, and most importantly, how to get rid of them.

What Are Drain Flies and What Do They Look Like?

Drain flies, also known as moth flies or sewer flies, are small insects that measure about 1.5 to 5 mm in length. They have a distinctive appearance with long, hairy wings and a fuzzy body. These insects are usually gray or brown in color and may have a mottled pattern on their wings. They are commonly found near sinks, drains, and sewage systems, which is how they got their name.

Are Drain Flies Harmful?

While drain flies may be a nuisance, they are not known to cause harm to humans. They do not bite or sting and are generally considered harmless.

However, since drain flies are commonly found in drains and sewers, they have the potential to carry disease-causing microorganisms from these unsanitary locations to the surfaces of your home.

What Causes Drain or “Sewer” Flies?

Once drain flies enter make their way into your home, they can turn from a minor irritation into a significant nuisance. Even in the winter, the freezing temperatures outside create an ideal environment indoors for these insects to thrive.

Before becoming fully-fledged adults, sewer flies go through a larval stage. The larvae are white or cream-colored and can be up to 9mm long. They have a worm-like appearance and are often found in the same areas as adult drain flies: the organic material buildup in your drains.

Drain fly larvae feed on decomposing organic matter, which is why they can often be found in dirty, moist environments like your home’s plumbing. It’s important to note that the presence of these larvae is usually a sign of a larger infestation.

How to Get Rid of Drain Flies

Fortunately, there are several ways in which you can get rid of drain flies in your home. Read on to learn some popular DIY methods.

Will Bleach Kill Drain Flies?

Bleach can kill drain flies, although it can take up to a day to see results. You can use a mixture of hot water and bleach to flush out drain flies as well as the organic material that they feed on. It’s also important to physically remove any buildup from drains and pipes using a drain cleaner and a brush or plumber’s snake.

Note that while bleach is powerful, it releases toxic fumes and can also permanently damage your septic system.

Setting Traps

Using traps is another way you can get rid of drain flies. Flypaper or sticky traps are readily available and can be placed near the infested areas to trap adult flies.

The problem with traps is that they address only the symptom (the adult flies) and not the root cause of the problem (the larvae residing in the organic buildup). If the larval habitat is not adequately treated and removed, new flies will continue to emerge.

Using Insecticides

Insecticides can be a powerful tool in the fight against drain flies. There are several types of insecticides suitable for this purpose.

Bacterial gels are often applied directly into the drains, where they break down organic matter that serves as a breeding ground for drain flies.

Aerosol sprays can also be used to kill adult flies quickly. They are best used in confined spaces such as bathrooms or kitchens.

Liquid bacterial gels, on the other hand, can be poured directly into the drain. These generally contain bacteria or enzymes that eat away at the organic material in the drain, thereby starving the drain flies and their larvae.

Always remember to use insecticides responsibly and follow the manufacturer’s instructions. Keep them out of reach of children and pets and ensure the room is well-ventilated while using these products. Afterwards, follow up with more thorough cleaning of the drain to ensure all larvae and eggs have been eliminated.

While insecticides can be effective, it is important to use them in accordance to their label instructions. Additionally, overuse or incorrect use of these products can result in the contamination of water sources, harming aquatic life and affecting the ecosystem.

DIY Natural Remedies for Sewer Flies

If you prefer to use natural methods for eliminating sewer flies, there are a few options you can try.

Using Insect Growth Regulators for Sewer Flies

One technique that can be used to eliminate sewer fly infestations over a period of time is using Insect Growth Regulators (IGR). These types of products are typically synthetic and mimic naturally occurring pheromones in sewer flies. They work to stop the reproductive life cycles of the flies, reducing the numbers over a few weeks. Although considered very safe, IGRs are usually used by professionals who are familiar with the specific products and techniques to incorporate.

Boiling Water

Pouring boiling water down your drains is one of the simplest methods to get rid of drain flies. The high temperature of the water helps to kill the adult flies, larvae, and eggs that might be in the drain. The water also helps to dislodge and remove the organic matter that the flies feed on. It’s a non-toxic and cost-effective method that can be used regularly to maintain clean drains.

Note: If you have PVC pipes, don’t use this method as the extreme heat can result in cracks.

Vinegar and Baking Soda

A concoction of vinegar and baking soda has been proven effective against drain flies. This natural remedy works because the fizzing action of the vinegar and baking soda mixture can effectively remove the grime and gunk that attract drain flies. To use this method, pour half a cup of baking soda into the drain, followed by half a cup of vinegar. Wait for about 15-20 minutes, then rinse with boiling water. This method not only helps to kill the flies but also leaves your drain clean and odor-free.

Homemade Traps

Setting up homemade traps is another natural method to get rid of drain flies.

One such trap involves using apple cider vinegar and dish soap. Simply fill a bowl or cup with apple cider vinegar, add a few drops of dish soap, and leave it near the drain. Drain flies are attracted to the scent of vinegar, and the dish soap traps them.

Alternatively, you can use a mixture of water, sugar, and dish soap. The sugar lures in the flies while the dish soap causes them to sink once they land on the liquid.

While the above methods may help you to temporarily eliminate drain flies in your home, they won’t help you combat a full-blown infestation.

Get Rid of Drain Flies for Good: Call a Professional

If you want to make sure all your bases are covered and get rid of drain flies for good, it’s best to call a professional exterminator like Dominion Pest Control. We’ve been serving residents of Lancaster and York Counties for over 25 years and possess the knowledge and tools to help you eliminate your infestation long-term.

At Dominion Pest Control, we take a comprehensive approach to drain fly extermination. Our first step is to conduct a thorough inspection and identify the main sources of the infestation. We then employ a professional-grade gel treatment that targets the fly larvae living in your drains, stopping the infestation at its source. This gel not only kills the larvae but also removes the organic material that drain flies feed on, disrupting their life cycle.

Additionally, our team uses specialized insecticides that are designed to quickly eliminate adult flies. Made by Nature-Cide, these commercial-grade sprays kill the flies on contact. Because our insecticides are formulated with natural ingredients like clove oil, cottonseed oil, and glycerin, they are also environmentally friendly and completely safe — even around children and pets.

We also offer advice and support on preventative measures like maintaining drain cleanliness and reducing moisture levels in your home — both essential items for preventing future infestations.

Once we eliminate the problem, our work doesn’t end there. At Dominion Pest Control, we also offer follow-up services to ensure that your infestation has been completely eradicated and that no further issues arise.


Drain flies may be a nuisance, but with proper cleaning and maintenance, they can be eliminated. If your drain fly problem persists, Dominion Pest Control is here to help. Call us today at (717) 393-7879 or contact us here for a free consultation.

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