5 Nasty Small Black Flies In the Bathroom, Not Drain Flies

If you’ve ever thought it’s only the drain flies that infest bathrooms, think again.

Drain flies feed on the waste in the bathroom drains and breed in them, as do other fly species.

The tiny size and black color of these little flies may trick you into thinking they’re drain flies. That’s a big mistake!

I’ve successfully cracked the code of small black flies in the bathroom, not fruit flies, and I will reveal what they are.

I’ll also chart out a step-by-step plan that eliminates these nuisance flies straight from their source.

Let’s get into it right away.

Fungus Gnats

Fungus Gnats - Small Black Flying Bugs In House Not Fruit Flies

Fungus gnats are tiny mosquito-like small black flies that live and breed in decaying organic wastes in a compost bin, trash can, and in wet soil bed of potted plants.

However, these flies are pesky bathroom pests.

It’s because like drain flies, fungus gnats also lay eggs in the gunk, choking the bathroom sink, shower, and bathtub drains.

Fungus gnats are 1/8 inches, equal to the drain flies’ size.

However, there are many visual, anatomical, and behavioral differences between drain flies and fungus gnats.

Drain flies are moth-like fuzzy flies that appear as tiny black spots on the bathroom floor, walls, and fixtures.

In contrast, fungus gnats are elongated bodies with long legs and a pair of long antennae. Their wings are dark with a veiny appearance.

Fungus gnats can’t fly in a straight line. And they’ve got a short flight pattern.

Their erratic and short flight path makes them appear as jumping bugs rather than flies when they take off.

Fungus gnats in the bathroom can spread from other areas of your home, such as the kitchen, basement, or potted plants where they lay their eggs.

When the fungus gnat infestation becomes severe, these small flies start showing up in clean areas of the house where there’s no food waste or moisture such as bedroom and living room.

These pesky flies tend to follow you both indoors and outdoors which makes them quite irritating.

Fungus gnats enter homes and bathrooms through the windows, through the small cracks and gaps on windowsills, and through bathroom vents.

Fruit Flies

Small black flies in the bathroom not drain flies

Fruit flies aren’t typically black or gray like the fungus gnat and drain flies. A fruit fly is tan or yellowish with red eyes.

However, if you notice fruit flies closely, you’ll find black overtones on their abdomen. These shades of black and their 1/8-inch body size make them appear like tiny black flies.

Fruit flies are oval-shaped, like house flies. But they’re tinier than the common house fly.

Ripe and rotting fruits and vegetables draw these fruit flies from the outdoors. They feed and lay their eggs in them.

However, fruit flies can also lay eggs in the gunk, choking the shower drain, bathroom, and kitchen sink drains, leading to a fruit fly infestation.

Like the drain fly and fungus gnat, the fruit fly is also a moisture bug.

Fruit flies inhabit moist areas and damp conditions, so the bathroom and kitchen has ample breeding sources for them to multiply.

Phorid Flies

Phorid Flies Look Like Fruit Flies In The House

Phorid flies, also known as humpbacked flies because of their hunched backs, are tiny tan to dark brown flies that breed in the decaying organic matter in the kitchen and bathroom drains.

Their body shape is oval, and their size ranges between 0.03 and 0.25 inches.

Phorid flies lay their eggs in organic debris and things like sewage systems, feces, and carcasses of animals and birds outdoors.

Their choice of breeding sites makes them harmful carriers of bacteria that they can transfer to our foods.

Phorid flies are also known as scuttle flies because they scuttle or scoot across the surface before taking off.

Phorid flies enter bathrooms from the outdoors, primarily through the windows and vents.

A severe phorid fly infestation on your property can also cause them to spill over from other areas of the house to your bathroom.


Why Mosquitoes Are In The House And Garage

Mosquitoes need no introduction. They breed in standing water sources and in damp areas.

Your bathroom is perfect for mosquitoes to breed if you have these two sources.

Mosquito infestations are common in properties with issues like piling waste and stagnant water.

Like all the bathroom flies on the list, mosquitoes enter homes from the outdoors.

Their breeding grounds can also exist in the house in areas like the basement or bathroom if there’s standing water in these areas.

Mosquito bites are risky. Though there are no mosquito-borne diseases in the US, but these biting flies can cause diseases like Lyme disease and dengue fever.

The Common House Fly

House flies are tiny flying insects that are present everywhere in the world. These flies are gray, ¼ inches in size, oval-shaped with a flattened abdomen, veiny transparent wings, and two large compound eyes.

Moist environments, organic debris, and food waste in bathroom trash bins draw these flies.

Uncleaned drains and the warmth of the bathroom, particularly after hot showers, make your bathroom a magnet for these flies.

These flies will breed in the damp areas of the bathroom, such as underneath sinks bathtubs, and in cracks or crevices in the bathroom floor and walls.

These skilled fliers enter bathrooms through the open windows, doors, and vents. Their tiny size also allows them to squeeze through any tight gap or crack on the windowsills of the bathroom windows.

Guide To Eliminate And Prevent Small Black Flies In The Bathroom

Fortunately, you’re not supposed to take separate steps for each of these flies to eliminate them from your bathroom.

Controlling moisture, ensuring proper ventilation, cleaning the drains, and some insecticide sprays are enough to get rid of these small black flies in the bathroom, not drain flies.

Clean The Drains

Clean the drains with a drain cleaner or a mixture of hot water, baking soda, and white vinegar to eliminate little flies in the bathroom.

The drains are the breeding grounds of all these flies, including drain flies. The slime choking the drains houses their eggs and their larvae.

When the flies’ larvae mature into adults, they pop out of the drain holes and appear as tiny black dots on the bathroom sink, fixtures, and floor.

Cleaning the drains removes the gunk and kills the fly larvae and eggs active in the drain.

Fix Water Leaks To Control Moisture

Leaking pipes underneath the bathroom sink and bathtub, dripping faucets, and other plumbing issues in the bathroom create standing water and moist environments.

The dampness in the bathroom also gives rise to molds and fungi that are food sources for these flies and many other bathroom bugs with no wings.

So, fixing the leakages is essential to keep your bathroom dry.

Treat The Indoor Plants’ Potting Soil

Fungus gnats lay eggs in the indoor plants’ potting soil. These eggs hatch and produce fungus gnat larvae which quickly mature into adult fungus gnats.

Treat the potting soil of your plants in the bathroom, and in the house, by mixing equal amounts of 3% hydrogen per oxide solution and water.

Drench the soil with the mixture and let it sit for a couple of hours to do it’s job. The mixture kills the fungus gnat larvae and eggs.

Clean The Bathroom

Regularly cleaning the bathroom and disposing of the bathroom waste daily go a long way to prevent fly infestations.

It removes the molds and wastes that become the food sources for these tiny black flies in the bathroom.

Using a citrus-based cleaner helps because the citrus smell is fly and bug-repellent.

Ensure there’s no fruit waste like fruit peels and rotting fruit in the bathroom trash can. They attract fruit flies and fungus gnats.

Follow a regular bathroom cleaning schedule or clean your bathroom at least once a month, especially during the summer when these little flies are active.

Ensure Proper Ventilation In Your Bathroom

Lack of ventilation in the bathroom causes condensation, which, again, leads to higher moisture content.

Ensure that your bathroom is properly ventilated. Installing an exhaust fan helps a lot in this case.

However, if your bathroom is spacious or you live in a hot and humid climate, installing a dehumidifier to control moisture and for proper ventilation will be best.

Fly Sprays

There are many fly sprays, especially pyrethrin-based sprays, which get rid of fruit flies, fungus gnats, and mosquitoes.

However, please read the safety instructions on the spray before using them. And keep them away from children and pets.

Fly Traps

Keep sticky yellow fly traps underneath the sink, near fixtures, and in the soil beds of bathroom plants.

The bright yellow color draws gnats. And when they sit in the trap, they get stuck.

It’ll be best to keep the traps for 24 hours and dispose of them with flies in them the following day.

You can also prepare homemade fly traps using apple cider vinegar, bowls or shallow pans, dish soap, and plastic wrap.

Spray Fly Repellents

Flies hate some scents. Two of the most effective natural repellents are the odor of eucalyptus and peppermint.

You can use the essential oils of these herbs as sprays by mixing a few drops of these oils in water.

Spray the mixture in your bathroom, especially in moist places such as underneath sinks and on the windows.

Keep Your Outdoor Area Clean

If there’s a mess outdoors, like in your yard, all the efforts to control the flies in the bathroom and home will come to naught.

These flies breed in rotting debris such as leaf litter, pet feces, wet soil beds, and the wastes in garbage cans and compost bins.

Follow a proper yard-cleaning schedule, like you follow a house or bathroom cleaning schedule.

I can’t stress how important it is.

Regularly dispose of the waste in the yard. Do not let food waste accumulate in the garbage disposals of your yard or garden.

These wastes are breeding grounds for flies where they lay eggs. The eggs produce maggots, which mature into adult flies, worsening the infestation.

Seal Cracks On The Windowsills

Small flies, bugs, and even wasps can get inside the bathroom by crawling through the crevices on the windowsills.

It’s the primary way of flies entering the home when windows are closed.

Caulk those gaps with a quality sealant, preferably with a silicone-based or polyurethane-based sealant. These sealants are waterproof, tough, and long-lasting.

Install Meshed Window Screens On The Bathroom Windows

How to get rid of mosquitoes in an apartment

The final step is optional. Installing meshed window screens on the bathroom windows and vents prevents flies and pests from entering through the windows.

The best part is that the window screens don’t hamper ventilation.

Monitor And Repeat

Tiny bugs and flies can be a pain in the back to eliminate. And most of the time, it’s not a one-time affair because these small pests have their way of raising their heads again.

So, monitoring and taking immediate action is vital for keeping these tiny pests off your property.

Professional Pest Control

Let’s face it, DIY ways have limitations. Lack of time and severe fly infestations can also come in the way of getting rid of flies in the bathroom.

If your repeated efforts fail, hiring a pest control expert to do the heavy lifting is best.

Frequently Asked Questions

Why Do I Have Tiny Black Flies In My Bathroom?

The organic waste build-up in the drains causes flies invasion through the bathroom windows and vents, potted plants, food wastes, decaying organic material, and excessive moisture issues cause flies in the bathroom.

Another reason is that flies in the kitchen and basement can spill over to your bathroom.

Are Small Black Flies In Bathroom Harmful To Humans?

Not all tiny black flies in bathrooms are harmful. However, flies like house flies and phorid flies can spread diseases. And mosquitoes are also carriers of diseases like dengue and Lyme disease.

Are Small Flies In The Bathroom Attracted To Light?

Yes. Flies such as fungus gnats and phorid flies are attracted to light.

Glowing light bulbs in the house and bathroom draw these flies indoors.


Drain flies, or moth or sewer flies, aren’t the only tiny flies in your bathroom.

Fungus gnats, phorid flies, house flies, mosquitoes, and fruit flies are five other flies that can breed in the bathroom waste.

Removing their breeding grounds, controlling moisture, and taking preventive measures to prevent them from returning are keys to keeping your bathroom free from these flies.

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