Drain Flies: Causes & Proven Elimination Tips [GUIDE 2025]

Stop drain flies in their tracks! Learn why drain flies appear, proven removal methods, and prevention tips. Trusted guide from Anta Plumbing.

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Annoyed by Tiny Flies Around Your Sink or Shower?

If you’ve ever noticed small, fuzzy, moth-like insects hovering near your drains, you’re not alone. These intruders are called drain flies, also known as moth flies, sink flies, or sewer gnats. While they don’t bite or transmit diseases, they’re a clear sign that something’s lurking in your pipes—and that something needs your attention.

Drain flies are not just a minor nuisance. Their presence often indicates clogged pipes, decaying organic waste, or even leaky plumbing hidden behind your walls. Understanding what causes them and how to get rid of them effectively can save you from a persistent pest problem.

What Are Drain Flies?

Drain Fly →  Small Furry-Winged Insect
Drain Fly → Attracted To → Organic Debris in Moist Areas

Drain flies are tiny insects (about 1/8 inch long) with hairy wings that give them a fuzzy, moth-like appearance. Despite their fragile look, they are incredibly resilient, especially in wet environments.

There are over 4,700 known species of drain flies. Most are harmless, but their ability to breed rapidly in moist, nutrient-rich environments makes them unwelcome visitors in bathrooms, kitchens, and basements.

These flies breed in the gelatinous slime that lines unclean pipes and drain traps. Each adult lives for about 2 to 3 weeks, but new generations emerge fast—so a few can turn into a full-blown infestation in days.

Why Do You Have Drain Flies?

If you’re seeing drain flies, it’s almost always because something in your plumbing system is providing the perfect breeding ground.

Common causes include:

• Clogged or slow-moving drains

• Leaking pipes hidden in walls or under floors

• Standing water or unused sinks

• Organic debris buildup in garbage disposals

• Cracks in shower grout trapping moisture

They’re particularly drawn to decomposing organic matter—think food scraps, hair, grease, soap scum, and even biofilm. Drains and pipes that haven’t been cleaned in weeks (or months) become the ideal nest.

 Signs of a Drain Fly Infestation

Drain Flies → Flying in Jerky, Random Patterns
Infestation → Detected By → Drain Tape Test

Here’s how to know if you’ve got a problem:

• Small, black or gray insects hovering near drains

• Jerky, erratic flight patterns

• Larvae or pupae visible in drain slime or near baseboards

• Persistent flies even after bleach or hot water use

✅ A simple way to confirm: Place duct tape over your shower or sink drain at night. If drain flies are present, they’ll get stuck trying to exit—and you’ll have visual proof by morning.

How to Get Rid of Drain Flies: Step-by-Step

Drain Fly Infestation → Solved By → Cleaning Organic Buildup

Once you’ve confirmed an infestation, it’s critical to not only kill the adults but also destroy the breeding site. Here’s how to eliminate drain flies permanently:

🛠 DIY Solutions

1. Clean the Drain Interior

   • Use a pipe brush or wire catcher to scrub inner walls.

   • Pour boiling water to rinse loosened debris.

   • Avoid relying on bleach—it often fails to dissolve the gelatinous nest.

2. Natural Enzyme Drain Cleaners

   • These break down organic waste without harming pipes or the environment.

   • Use for several nights before bedtime (low water flow times).

3. Use the Tape Trap Test Again

   • After cleaning, reapply duct tape.

   • If no flies appear after 3–5 days, infestation is likely resolved.

Prevent Future Infestations

Drain Fly Prevention → Maintained By → Routine Cleaning & Leak Fixing

Preventing drain flies is easier than dealing with them. Here’s how:

• Clean all sink and shower drains weekly.

• Avoid food scraps going down the kitchen sink.

• Use enzymatic cleaners monthly for maintenance.

• Fix leaky faucets, grout, or under-sink pipes—these create moist breeding spots.

• Run water through unused sinks or guest bathrooms weekly.

 Drain Flies vs. Other Household Flies

Drain Flies  FAQs

What attracts drain flies to my home?

Drain flies are drawn to moist, dark spaces with decomposing organic waste—like unclean pipes, leaky drains, and unused sinks.

Are drain flies harmful?

Drain flies don’t bite or spread disease, but their presence indicates poor plumbing hygiene and potential organic buildup.

Can I kill drain flies with bleach?

Bleach often fails to dissolve the organic slime where drain flies lay eggs. Mechanical cleaning and enzyme cleaners work better.

How do I know where drain flies are breeding?

Use the tape trap method: cover drains at night and check for trapped flies in the morning. The source is usually below the taped drain.

Should I call a plumber for drain flies?

If DIY cleaning fails, or you suspect pipe damage or hidden leaks, a professional plumber can perform camera inspections and hydro-jetting.

Sources

• https://bpca.org.uk/news/i-spy-my-little-drain-fly-an-in-depth-look-at-drain-fly-control-05062023%5B1
• https://entomology.ca.uky.edu/ef615%5B2
• http://ipm.ucanr.edu/PMG/PESTNOTES/pn74167.html%5B3
• https://edis.ifas.ufl.edu/publication/IN1226%5B4
• https://flytrick.com/blogs/news/detailed-study-on-the-life-cycle-growth-conditions-attractants-dangers-and-prevention-of-psychodidae-moth-flies%5B5
• ttps://edis.ifas.ufl.edu/publication/IN1226
• https://en.wikipedia.org/wiki/Psychodidae