Drain fly extermination

If you’re seeing many small, moth-like flies in your bathroom, basement or kitchen, you may have an infestation of drain flies. Known also as moth flies, sink flies or sewer gnats, these little insects are not only a nuisance, but they’re a sure sign that your drains need cleaning. That’s because sink flies lay their eggs in the gelatinous scum that can build up on the walls of your drain pipes.

Contact our experts

    Elite Pest Control to the rescue!

    If you’re wondering how to get rid of your drain fly problem, and how to prevent the flies from coming back, we have some resources for you. Let the expert technicians from Elite Pest Control coach you in identifying the flies and give you some DIY tips for getting rid of them. If professional prevention and drain fly extermination are required, we’ll come right to your home to solve the problem—we have pest-management teams in Gatineau, Laval, Montreal, Repentigny, St-Jérôme, Trois-Rivières and elsewhere throughout Quebec.

    Identifying the problem

    The drain fly is a true fly from the Psychodidae family. Adult specimens resemble small moths, as their wings and bodies are covered by a furry layer of grey hairs. Indoors, you’ll most commonly notice them gathering around sinks, walls and windows, where their characteristic hop-and-fly movements set them apart from other flies.

    Typically, they stay close to the areas where they lay their eggs. This includes floor or sink drains such as those found in bathrooms, basements and kitchens. They might also lay their eggs around:

    • Showers
    • Bathtubs
    • Leaky washing machines
    • Plumbing systems
    • Storm drains
    • Sewers or sewage treatment facilities
    • Sump-pump pits

    Larger populations of these flies have been known to flourish in infrequently used residences, such as summer homes, or in drains that have been damaged and are not draining properly.

    Are drain flies harmful?

    Drain flies are more a nuisance than a harmful pest, as they’re not known to transmit pathogens to humans. However, it’s important not to let them linger in your home. Here’s why:


    1. They’re hard to get rid of. The small size of drain flies makes it easy for them to pass through mesh drain covers. The longer you leave the problem, the bigger it will grow.


    1. Their presence is unpleasant. The presence of bugs doesn’t necessarily mean your home or business isn’t clean, but a cloud of sink moths in the bathroom or kitchen could colour the impression you give visitors. It’s also inconvenient to leave dirty smudges on walls and tiles every time you kill one with a fly swatter.

    Drain flies might also be an indication that there has been a break or backup in the sewer system.

    Physical description

    Drain flies are small, usually from 1 to 5 mm in length. Their silvery grey fur ranges from the head and body to the wings, which are broad, rounded and typically held at an angle above the body. The wings aren’t designed to fly any kind of distance, which accounts for the erratic flying and walking pattern of these insects.

    The drain fly lays its eggs in clusters that contain from 30 to 100 eggs. Larvae emerge within 48 hours of laying. The larval stage lasts between 9 and 15 days, while the pupae remain in that stage for only about 20 to 40 hours.

    The larvae and the pupae are cylindrical and somewhat longer than the adult flies, usually 4 to 5 mm in length. They’re sometimes called “maggots” during these phases. These early-stage sink flies thrive in the moist decaying matter that lines your sewage and grey-water drains.

    Sink flies get the oxygen they need by extending a breathing tube towards the surface of the gelatinous scum they’re embedded in.

    How to get rid of them

    The first step in getting rid of drain flies is to figure out where the flies are laying their eggs. Once you find the drain in question, you’ll need to clean the drain pipes or have the job done by a professional exterminator or plumber. This is usually enough to solve the problem.

    If you’re doing the job yourself, use a home-plumbing product designed to dissolve and remove clogs and organic buildup. Next, use a specially designed brush or sewer snake to scrape clean the walls of the pipes. Don’t forget the overflow drain on sinks and bathtubs, and be sure you open and thoroughly clean out the P-trap (U-bend).

    In a nutshell, what you need to remember is that drain fly prevention is essentially a matter of performing regular home maintenance:

    • Clean drains on a frequent basis
    • Don’t allow standing water to linger in the kitchen, bathroom or basement
    • Repair sewer system leaks or backups immediately

    If sink flies continue to reproduce in your home or place of business, contact us and book a free inspection. A certified Elite Pest Control technician will find the source and exterminate these nuisance flies safely and effectively.