Drain flies, also known as moth flies or sewer flies, are small, fuzzy insects often seen in bathrooms and kitchens. These tiny, moth-like creatures are characterized by their hairy bodies and wings that they hold in a roof-like manner when at rest.
Where Drain Flies Live and Thrive
Drain flies are primarily found in environments with standing water and decaying organic matter. Their preferred habitats include household drains, sewage systems, septic tanks, and areas with moisture accumulation like leaky pipes or neglected garbage disposals. The larvae of these flies feed on the gelatinous film, also known as biofilm, which consists of algae, bacteria, fungi, and other microorganisms that build up on the inner surfaces of pipes and drains.
Females lay their eggs, typically 15 to 100 at a time, in these moist, nutrient-rich films. Eggs hatch within 30 to 48 hours, and the larvae then develop, feeding on the organic material for approximately 9 to 24 days. After a pupal stage lasting one to five days, adult flies emerge. Adults are weak fliers and are often found resting on walls or surfaces near their breeding sites, entering homes through drains, small cracks, or open windows.
Are Drain Flies Harmful?
Drain flies are not harmful to humans. They do not bite or sting people or pets, as they lack the mouthparts necessary for such actions. While they are not known to directly transmit diseases to humans, their presence can indicate unsanitary conditions, such as a build-up of organic matter in drains.
These flies can carry bacteria and pathogens from the dirty environments they inhabit, like sewers, to surfaces in your home, including food preparation areas. In some individuals, the fragments and dust from their decaying bodies can become airborne and may aggravate respiratory symptoms.
Controlling Drain Fly Populations
Managing drain fly infestations primarily involves eliminating their breeding sites. This means thoroughly cleaning drains and other areas where organic matter and stagnant water accumulate. Using a stiff brush to scrub the inside of drain pipes and applying enzymatic drain cleaners can remove the biofilm that serves as their food source and breeding ground. Pouring boiling water down drains can also offer a temporary solution by dislodging some of the organic material.
Beyond drains, address other potential breeding locations, such as leaky pipes, neglected garbage disposals, overly moist soil in potted plants, or standing water in refrigerator drip pans. Maintaining a clean and dry environment helps prevent future infestations. For severe or persistent drain fly problems that do not respond to household cleaning, consulting with a pest control professional is a good next step.