Buzz
To eliminate drain flies, you need to do what’s essential—clean your drains. Credit: yuri of yuriyuri/ShutterstockKey Points
- Drain flies—also known as moth flies, sewer flies, or filter flies—flourish in damp environments where they can feed on organic materials, such as drains, sewers, and moist soil.
- To eradicate drain flies, it’s vital to locate and clean their breeding grounds, as simply killing adult flies won’t solve the issue. Effective cleaning methods include pouring boiling water down drains or using a mixture of baking soda, salt, and vinegar to eliminate organic buildup where flies breed.
- Preventive steps include regularly cleaning drains to remove potential breeding grounds and sealing any entry points to stop flies from infiltrating the home.
If you're doing the dishes and spot tiny, fuzzy flies about the size of a shoestring darting from your kitchen sink like fireworks on the Fourth of July, you may have a drain fly issue. As their name suggests, these flies breed in drains.
Like most flies, drain flies are typically 1/16 to 3/16 inches (1.5–5 millimeters) long with six legs, wings, and antennae. Their bodies are pale gray or tan, and they are easily recognized by the fine hair covering their body, antennae, and wings, giving them a fuzzy — some might even say endearing — appearance. This is also why they're sometimes called moth flies, due to their resemblance to moths.
Frank Meek, technical manager at Orkin and a board-certified entomologist, points out that drain flies are also known as sewage flies or filter flies. These names originate from typical breeding and development areas for the pests, as he explains in an email.
Moist areas, especially those laden with food scraps, sewage, decaying plant material, and other organic waste, are prime breeding grounds for these flies. Sinks, storm drains, shower drains, septic tanks, compost piles, and even piles of dog waste in the backyard can all become a luxurious feast for them.
This drain fly, also known as the moth fly (Clogmia albipunctata), measures approximately 2 millimeters in length. Sanjay Acharya/CC BY-SA 3.0/WikipediaLike all insects, drain flies don't stick around to care for their offspring. Instead, they leave their eggs in places where they feed: food waste, feces, logs, or in your sink. However, their preferred breeding ground in and around your home is usually soil.
"Moist soil is their preferred breeding habitat, whether it's in pre-mixed soil, a potted houseplant, or beneath your home. Because this activity occurs out of sight, homeowners often don’t realize there’s a problem until the fully grown drain flies start appearing in kitchens and bathrooms," says Meek.
Once the eggs hatch into small white larvae, it takes about 8 to 24 days for them to mature. As adults, their lifespan is a short two weeks, which is much shorter compared to a housefly, which can live up to a month.
What to Do if You Have Drain Flies
Meek notes that you’re most likely to find them resting on walls, as flying isn’t their strong suit. "Drain flies are weak fliers, so indoors, they’re often seen crawling on walls or other surfaces," he explains. If you suspect a drain fly invasion, try observing your kitchen after dinner. "Their peak activity occurs in the evening when they may fly or hover above drain openings indoors or sewage filter beds outside."
The good news is that having drain flies doesn’t mean your home is filthy. It typically indicates a slow or clogged drain.
"Drain flies congregate, mate, and lay eggs in moisture or stagnant water. The slimy film that builds up in sewers and drains is their favorite breeding and feeding spot. Neglecting regular cleaning and maintenance of these areas can attract the pests and provide them with a place to feed and grow," Meek adds.
Though there are rare cases where inhaling drain fly body parts might trigger bronchial asthma, these pests are not known to transmit serious diseases to humans or large animals, Meek says. However, that doesn’t mean you should delay getting rid of them. Drain flies can land on your charcuterie board and spread bacteria; that’s a bit much, even for a blue cheese lover.
How to Remove and Prevent Drain Flies
If you spot these fuzzy flies emerging from your drain while doing the dishes, it’s time to take action. Here's what you need to do:
- Find the breeding site. "A thorough inspection is essential to locate the breeding site, so check a variety of places – drains, dirty trash bins, saucers under potted plants, birdbaths or feeders, clogged roof gutters, storm drains, air conditioners, cooling towers, damp compost, and rain barrels," advises Meek. Also, inspect around your sewer or septic tank if you have one. "Once organic material and larvae are removed, the problem is resolved, except for the adult flies. These will survive for about 20 days but will have nowhere to lay eggs to continue their life cycle," he adds.
- Clean your drains. However, regular drain cleaners won’t fix the issue, according to Meek. "Foaming enzymes applied by pest control experts break down the film coating that drain flies feed on, and they may even target drain fly eggs, preventing further breeding. This method is safe and won’t harm plumbing," he explains. Another method is using an ultra-low volume (ULV) fogging machine to kill the flies, but this only addresses the adult flies and doesn’t resolve the breeding site, so it doesn’t provide lasting control.
- Avoid pouring bleach down your drain. "While bleach may kill some larvae, it moves too quickly through the drain to penetrate the thick buildup where the female drain fly deposits eggs. As a result, it generally doesn’t eliminate drain flies," says Meek. Additionally, bleach is corrosive and can damage older pipes. And above all, never mix bleach and ammonia down the drain, as this can create toxic chlorine gas, which can be fatal if inhaled.
Professional help may be necessary to clean your drains.
tirc83/Getty ImagesNatural Solutions to Get Rid of Drain Flies
Here are some non-chemical methods to eliminate and prevent drain flies, thanks to This Old House:
- Boil water and pour it down your drain twice weekly to clear away any buildup.
- Leave a mixture of baking soda, salt, and vinegar in your drain overnight, then flush it with boiling water the following day.
- Place a bowl with a combination of vinegar, soap, sugar, and water on the kitchen counter. The flies will be drawn to the sweet, sugary scent and become trapped in the sticky soap.
- If you only have apple cider vinegar, that will work as well. Pour it into a container, seal it tightly with plastic wrap, and poke several small holes in the wrap to let the flies in but prevent them from escaping.
You’ll still need to identify and address the breeding site to prevent the drain flies from coming back.
Drain fly larvae are intriguing in a weird way—they lack eyes, legs, and noses. Instead, they have a breathing tube that extends from one end of their body to allow them to breathe.
