What Are the Drain Flies and How to Get Rid of Them?

What Are Drain Flies?

If you've ever noticed tiny, fuzzy flies hovering around your sink or bathroom drains, you're likely dealing with drain flies. Also known as moth flies, sewer flies, filter flies, or bathroom flies, these pests belong to the species Clogmia albipunctata and are members of the Psychodidae family. Though small—about 1/16 to 3/16 of an inch in length—their hairy, moth-like appearance makes them easy to spot once you know what to look for.

Despite their resemblance to moths, drain flies only have two wings, which feature distinctive parallel veins. Their wings, legs, and antennae are covered with fine hairs, which help them repel water and survive in damp environments.

Why Do I Have Drain Flies in My House?

Drain flies love moisture. In nature, they live in swamps, wet wooded areas, or anywhere with decaying organic matter. But in homes, they thrive in places where standing water and slime accumulate—especially in dark, damp areas.

Common Places You’ll Find Them Indoors:

• Bathroom sinks, showers, and bathtub drains

• Toilet tanks and the bases of leaky pipes

• Floor drains in laundry rooms or basements

• Unused guest bathrooms with stagnant water

• Under-sink cabinets with moisture issues

• Around AC units and refrigerator drip pans

Outdoor Sources:

• Clogged gutters

• Standing water in plant saucers

• Overflowing trash bins

• Yard drains or poorly graded areas

• Sewer systems or septic tanks

If you're seeing them consistently, it's a sign that there's a hidden source of moist organic matter nearby. The more neglected a drain or water source is, the more appealing it becomes to these little invaders.

The Life Cycle of a Drain Fly

To effectively stop a drain fly infestation, it helps to understand how they live and reproduce. Their life cycle is fast and resilient, which is why infestations can grow quickly if not handled early.

Egg Stage: Females lay 30 to 100 eggs at a time in moist, decaying organic material—like the gunk inside your drain.

Larval Stage: The larvae, which look like tiny worm-like creatures, feed on sludge, algae, fungi, and bacteria inside pipes. This stage lasts about 9 to 18 days.

Pupal Stage: After feeding, larvae pupate for about 5 days before turning into adults.

Adult Stage: Adult drain flies live 1 to 2 weeks. They don’t bite, sting, or spread disease, but they reproduce rapidly—leading to more eggs and more flies.

The entire life cycle takes about 3 weeks. That means if you don't break the cycle, the infestation will just keep coming back.

Are Drain Flies Dangerous?

No, drain flies are not dangerous in the traditional sense. They don’t bite or sting, and they aren’t drawn to human food like fruit flies or house flies.

However, their presence is a red flag. Since they breed in places filled with bacteria—like stagnant water and sewer lines—they can indirectly indicate a sanitation issue. In rare cases, very large infestations can aggravate respiratory conditions or suggest leaks and pipe damage.

Bottom line: drain flies aren’t harmful, but they are annoying—and they signal that it’s time to clean up.

How Do I Know Where Drain Flies Are Breeding?

Tracking the breeding site is key to eliminating drain flies. Here are some easy ways to identify where they’re coming from:

Plastic Wrap Test: Place plastic wrap over the suspected drain and check it the next morning for flies.

Oily Glass Trap: Invert a clear glass with a bit of vegetable oil inside over the drain. If flies are inside by morning, you’ve found the source.

Manual Inspection: Use a flashlight and check inside sink or tub drains. If you see slime buildup or small larvae, you’ve got a breeding site.

Don’t forget to check multiple drains—infestations can stem from more than one location.

The Right Way to Get Rid of Drain Flies

Killing the adult flies won’t solve the problem. You need to eliminate their breeding grounds. Here's a step-by-step guide:

Step 1: Scrub the Drain Thoroughly

Start by removing any drain covers and using a long pipe brush or stiff wire to scrub the inside of the pipe. Focus on the slime that builds up near the top where water doesn't flow as often.

Step 2: Pour Boiling Water (Optional)

Pouring boiling water down the drain can help loosen organic matter. However, drain fly larvae are pretty tough and may survive it, so don’t rely on this method alone.

Step 3: Use a Drain Gel or Enzyme Cleaner

Use a biological drain gel or enzyme-based cleaner specifically designed to break down organic sludge. These are safe for pipes and more effective than bleach or harsh chemicals.

Avoid using insecticides down the drain—they’re not effective and could damage your plumbing or the environment.

Step 4: Repeat the Process

Drain flies are resilient. Continue treatment daily for at least 2 to 3 weeks to fully break the life cycle.

Home Remedies and Natural Drain Fly Control

Looking for non-chemical methods? Here are some effective natural ways to deal with drain flies:

DIY Drain Trap: Mix sugar, vinegar, water, and dish soap in a bowl. Leave it near the drain overnight to catch adults.

Baking Soda + Vinegar: Pour 1/2 cup of baking soda followed by 1/2 cup of vinegar into the drain. Wait 30 minutes, then flush with hot water. It won't kill larvae but can help loosen buildup.

Essential Oils: Some people swear by peppermint, eucalyptus, or lavender oil around drains to repel flies. While not scientifically proven, it’s worth a try for light infestations.

Dry Out the Area: Reducing humidity and moisture levels in your home will make it harder for drain flies to survive.

What If I’ve Cleaned Everything but Still See Drain Flies?

This is a common frustration. If you've scrubbed all the obvious drains and still see drain flies, you might be missing a hidden breeding ground.

Hidden Sources Could Include:

• Broken pipes beneath your slab foundation

• Moisture in crawlspaces or wall cavities

• Unused appliances like dishwashers or washing machines

• Commercial drain pans, elevator pits, or sump pits

In these cases, it’s best to call a licensed plumber or pest control expert to inspect for leaks or hidden infestation zones.

Can I Use Insecticides or Bug Sprays?

Most household insect sprays won’t work on drain flies. That’s because their larvae are inside drains—not out in the open.

What you can use:

• Sticky traps near windows and sinks to catch adult flies

• UV light traps to reduce adult populations

• Insect growth regulators (IGRs) in commercial or industrial settings

What you shouldn't do:

• Don’t pour pesticides or bleach down the drain

• Don’t try to bomb your house—larvae will remain untouched inside pipes

Preventing Future Drain Fly Infestations

Once you’ve gotten rid of drain flies, keep them from coming back with a few simple habits:

• Clean all drains weekly with enzyme cleaners

• Run water through infrequently used drains (like guest bathroom showers)

• Fix leaks and seal cracks around pipes

• Improve ventilation in bathrooms and kitchens

• Don’t leave standing water in buckets, trays, or planters

Drain flies love moisture and grime. Eliminate both, and you’ll eliminate them.

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Frequently Asked Questions About Drain Flies

1. What causes drain flies in the first place?
   Drain flies show up wherever there’s stagnant water, decaying organic material, and poor sanitation—usually inside drains or hidden leaks.

2. What kills drain fly larvae in drains?
   Scrubbing the pipe walls and using enzyme-based drain cleaners will kill larvae and eliminate their food source.

3. Will bleach or boiling water kill drain flies?
   Not effectively. Larvae are protected by biofilm and fine hairs. These methods may help, but are not a complete solution.

4. Are drain flies harmful or just annoying?
   They’re mostly a nuisance and don’t spread disease, but large infestations can indicate underlying plumbing problems or sanitation issues.

5. How do I permanently eliminate drain flies?
   Eliminate standing water, clean every possible drain, treat for 2–3 weeks, and prevent future buildup with regular maintenance.