Drain flies, also known as sink flies, sewer flies, moth flies, or sewer gnats, breed due to the accumulation of moist organic matter in your sink.
Before the situation gets out of hand and you need to spend money calling in professionals, I have two solutions to help you kill them.
Even the most mindful people in charge of a home kitchen let bits of food down the drain.
Drain flies have short, hairy bodies, and with their wings open, they look like tiny moths.
Over the past 20 years, we’ve faced the fly dilemma in the kitchen twice.
In our kitchen, we’ve also had to deal with pantry pests such as fruit flies, household ants, and flour mites, also known as weevils.
Thankfully, I found solutions to tackle pest infestations using natural products without spending a fortune.
Although we are mindful of what goes down the sink, we both admit we are not smart about ensuring nothing gets past the drain, and it happens.
It’s not done on purpose, nor do we pour oils or bacon grease down the pipes, as that can cause a primary backup and a fortune for a plumber.
Today, I want to discuss the steps we took to eliminate drain flies from our kitchen fast before the situation got out of hand.
Fruit Flies vs. Drain Flies – Know The Difference
At first, I thought the flies were fruit flies, so naturally, I made my homemade apple cider vinegar and dish soap concoction to eliminate them.
Not one flying nuisance went for the bait, so I knew they had to be a different kind of fly.
I did my best to get a close-up photo of the flies, as they are tiny, like fruit flies.
They don’t stay still long enough.
Drain flies usually breed in the slimy organic film inside drains and other persistently damp areas, while fruit flies are more often associated with fermenting fruit, vegetables, and other sugary organic material.
Here’s a chart I created to show you the differences between the different fly breeds.
Places You Might Find An Infestation
You may not believe drain flies are coming from the drain; however, it’s common, especially during the hot, humid summer months.
Believe it or not, drain flies can come from the toilet in your bathroom, the bath, the shower, and the sink.
They can appear anywhere there is humidity, heat, and organic matter that can mould, ferment, gel, and turn into a blob of grossness.
Check the sump pump, sinks, bathrooms, and floor drains in the basement for fly infestations.
Finding Drain Flies In The Bathroom
You may find drain flies in your bathroom, especially around the sink, tub, and shower areas.
You’ll also see them hovering around the mirrors, perhaps because they like to look at themselves.
Large amounts of hair and dead skin end up trapped in the drain, turn into a gel substance, and are ripe for drain fly breeding.
First, you will want to deep-clean and clear the drains, removing as much gunk as possible.
We bought long, rigid, orange drain gunk removal tools from Temu for cheap, but I’m sure the Dollar Store or hardware stores carry them.
Plastic drain snakes are also available at Amazon Canada for under ten dollars.
Slide the plastic tool into the drain, and the ridges on the side will catch the hair and anything else that gets in.
The most important step is removing the slimy organic buildup where drain fly larvae live. A drain snake helps with hair and debris, but a long stiff drain brush can scrub the film from the sides of the pipe.
After cleaning, keep checking the drain for activity and repeat the mechanical cleaning if you still see flies. Persistent activity can mean another drain or damp area is the true breeding site.
How To Get Rid Of Drain Flies Fast
If you are unsure whether a drain is the breeding source, place a strip of clear tape sticky-side down across part of the drain overnight without sealing the opening completely. Flies caught on the tape can help confirm the source.
However, if you don’t see any flies, that doesn’t mean you don’t have them. They may be in another drain in the home.
Repeat the process until you find the breeding ground, then kill it using the intense cleaning process below.
What You Will Need:
- A long stiff drain brush or drain snake
- Hot water that is safe for your plumbing
- An enzyme or bacterial drain cleaner, optional, used exactly as the label directs
Use a drain snake to remove hair and reachable debris, especially in bathroom drains, then scrub the inside walls of the drain with a stiff brush to remove the slippery organic film.
Flush the loosened debris with hot water that is appropriate for your plumbing. If you are unsure whether very hot or boiling water is safe for your pipes, use hot tap water or follow your plumber’s guidance.
If you use an enzyme or bacterial drain cleaner, apply it only as directed on the product label. The goal is to break down the organic film after the physical cleaning.
University extension guidance emphasizes that physically removing the organic film is the most effective control step. Virginia Tech notes that vinegar alone is not very effective for drain flies because it does not penetrate the accumulated material. See the Virginia Tech drain fly guide and the University of Maryland Extension guide.
After cleaning and flushing, monitor the drain rather than sealing it with chemicals or repeatedly pouring mixtures into the pipe.
Keep monitoring for new adults after cleaning. Drain fly development can take roughly one to four weeks depending on conditions, so seeing an occasional adult for a short time does not necessarily mean the cleaning failed.
Homemade Drain Fly Spray: What Actually Matters
We originally tried a homemade spray after cleaning the drain, but a spray only deals with the adult flies you can see. It does not remove the breeding material inside the drain.
You can use the spray in areas where flies gather, including all drains.
If adults are still flying around after the drain has been cleaned, vacuuming them up or using a sticky trap is a simple temporary control while you continue looking for the breeding source.
I no longer recommend spraying isopropyl alcohol into drains. It is flammable, and treating the adults does not solve the underlying buildup where the larvae develop.
For the safer approach, use:
- A stiff drain brush or drain snake
- Hot water that is safe for your plumbing
- An enzyme or bacterial drain cleaner, if needed, used according to its label
- A vacuum or sticky trap for the remaining adult flies
Extra Tip For Heavy Infestation
If you have a large infestation after thoroughly cleaning one drain, inspect nearby sinks, tubs, floor drains, overflow openings, condensate pans, and other damp areas. If you cannot find the source or suspect a leak or sewer issue, call a plumber or pest-control professional.
You Don’t Need To Suffer
Once the breeding material has been removed, the number of adult drain flies should decline. Continue monitoring because adults may still emerge for a while after the initial cleaning.
For prevention, periodically clean drain stoppers, overflow openings, and the inside walls of slow or infrequently used drains so organic film does not build up again.
Be proactive with cleanliness in your home. It’s just another job to add to the task list.
Discussion: Have you ever dealt with drain flies in your home? How did you fight them off?
Please leave any comments or questions below.
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Mr. CBB