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How to Get Rid of Drain Flies, Step by Step

View of the sink, drain and flowing water
Phichai / Shutterstock

Whether you live in an apartment or single-family home, flies can be a constant problem. Leaving the door or window open for too long will let these pests inside and garbage left out for too long could attract even more. Drain flies can be especially annoying and difficult to get rid of.

This guide shows you how to identify drain flies, offers step-by-step tips for how to get rid of drain flies, and helps you to determine when it may be time to call a professional for help.

What do drain flies look like?

Drain flies are extremely small, measuring somewhere between 2 and 5 millimeters in length. These flies have small round wings and are usually gray in color. Also known as filter or sewer flies, they’re attracted to standing water and don’t fly very well. They usually get from surface to surface by jumping. With eggs that can hatch every 48 hours, these flies tend to live for up to three weeks before they die.

Contrary to popular belief, drain flies do not bite humans.

Tiny drain fly

Nitin Chandra / Shutterstock

How do you get drain flies?

Drain flies normally do not get into the home through your drains. While they may congregate near drains and sinks with sitting water, drain flies usually enter the home through extremely small holes. Even if you’ve closed your windows and doors properly, it is possible to have a drain fly infestation.

Drain flies do not pose any type of immediate threat other than being a nuisance. A rare possibility does exist that drain flies could be a carrier of disease because they tend to congregate around standing water and sewage.

How to check for drain flies

Drain bugs like to congregate around standing water, drain pans, and pipes. If you think you have a drain fly problem, place some tape over your drains for at least one full day, and then inspect the other side of the tape.

For a possible drain fly infestation in your yard, use a plastic cup to cover any open water drains and then check the cup after a few days. Drain flies usually start congregating in the cup as they look for a way out.

If you think your pet may be infested with drain flies, use a fine-tooth pet comb to inspect every part of his body. Make sure to brush the fur back far enough so that the skin is visible.

How long can drain flies infestations last?

Drain fly infestations normally last up to 20 days, which is the total lifecycle of the insect. If you don’t catch the infestation, drain flies can reproduce quickly and start the cycle all over again.

If you discover a drain fly infestation, remove all standing water, sewage, and anything that smells. This will help shorten the total time of infestation.

How to get rid of drain flies, step by step

In most cases, if you can learn how to get rid of drain gnats and follow these steps, you won’t have to seek professional help. You’ll want to start the removal process immediately after discovering the infestation because drain flies can lay eggs, hatch, and repeat the life cycle.

Step 1: Unclog any drains

Drain flies are happiest when they’ve found a clogged or slow-moving drain. Make sure you take care of these drains first by unclogging them.

Step 2: Clean the drains

You’ll need to remove all decomposing junk in your drains. You’ll need to run warm water down the drain and use a snake to remove as much as you can. Snakes are tools that are often used to effectively unclog drains and come in the form of a metal hose. Remember to use a gentle scrubbing motion to remove as much grime as possible.

Step 3: Clean the U-trap

Open and clean the U-trap that’s located underneath your sink. Drain gnats will often congregate there as well.

Step 4: Use an enzyme cleaner

To remove any particles left over after cleaning your drains with a snake, pour an enzyme cleaner or Drano down the drain. While Drano will help get the job done, the enzyme cleaner provides the most coverage within the pipe and leaves behind a layer of chemical that ensures the smooth passage of grime and particles in the future.

Step 5: Rinse your drain

After the predetermined amount of time has passed since you poured the enzyme cleaner or Drano in your pipes, it’s time to rinse with warm water. Let the water run for two to three minutes before turning it off.

Following these steps should effectively eliminate the breeding ground of any drain flies. If you still notice a significant amount of drain flies after two weeks, you’ll need to check and clean other drains in the house using the same steps.

Products you can use to treat a drain flies infestation

  • Natural Armor Fruit and Drain Fly Killer: This gel solution works on both drain flies and fruit flies and simply needs to be poured down the drain after running warm water.
  • InVade BioDrain Solution: This product uses citrus oil and microbes to target a variety of flies, including drain flies.
  • Pest Peeve: This drain treatment incorporates both chemicals and natural ingredients. It also leaves a sweet grape scent in the drain after the treatment is completed.
  • American Bio-Systems Drain Gel: This drain and fruit fly killer uses a gel to control future infestations.

Don’t want to use chemical cleaners? Here’s how to get rid of drain flies naturally

Chemicals aren’t always the answer when looking for an effective way to kill drain flies. Natural, home remedies could do the trick if you’ve got the necessary items in your home.

First, grab a metal snake and slowly push it around the drain as much as possible. Then pour boiling water down the drain. To see if you’ve got any flies left, fill a bowl with an equal amount of sugar and vinegar, and add up to 10 drops of dish soap. Place the bowl next to the sink. Drain flies will smell your mixture and drown once they land in the bowl.

Another natural, homemade drain cleaner involves mixing a half cup of salt, half a cup of baking soda and one cup of vinegar into a bowl, and pouring it down the drain. After letting the mixture sit overnight, pour boiling water down the drain.

When to call a professional exterminator to treat drain flies

A drain fly infestation shouldn’t last for more than 20 days. If you’ve tried to remove drain flies by yourself with the steps above on all of your drains and flies are still noticeable in your home, a professional exterminator might be your best option.

How to keep drain flies out of your home

Unlike other insects, drain flies have the ability to enter your home through the small openings in your window and door screens. If drain flies smell something they like in your home, they’ll find a way to get in.

The best way to keep drain flies out of your home is to clean your drains every other week using a mixture of salt, baking soda, and vinegar, followed by boiling water. Make sure to keep your doors and windows closed as much as possible to prevent them from finding a way to their desired breeding ground.

Lastly, because drain flies love water and sewage, make sure any standing water is removed and the area is cleaned immediately.

The bottom line on drain flies

Drain flies are of little cause for concern as disease carriers. Even though they’re mostly found near contaminated water, they don’t venture away from their food source and they don’t live long enough to travel long distances. If an infestation is apparent, homeowners should still take proper steps to eradicate it and create a plan for regular drain cleaning to avoid future issues.

Frequently Asked Questions

Are there different species of drain flies?

There are six subfamilies of drain flies and 2,600 different species. The vast majority do not carry any type of disease and most species live in humid climates.

How long should I wait to run warm water after using a drain treatment?

The amount of time you wait depends on the treatment. While most brands require the chemical to sit in the drain overnight, it’s best to follow the manufacturer’s instructions.

How many eggs does a drain fly lay?

Female drain flies will lay between 30 and 100 eggs just above the waterline where most sewage and contaminates are located.


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