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Yes the tiny flies in your bathroom are drain flies

As a Service Partner client, Lynette recently sent me a photo of her bathroom floor covered in tiny flies. It didn’t take me long to identify them as drain flies, which thrive in warm temperatures above 20°C, especially in spring and summer. Unfortunately, Lynette’s attempts to kill them were futile, as the flies kept coming back.

She was baffled and frustrated that they only appeared in one bathroom, accumulating on the walls and floor while absent in the rest of the house. The photo above shows the astounding number of flies that can exist in a small area.

Cleaning your bathroom won’t eliminate these pesky flies

Despite her rigorous cleaning routine, Lynette was fed up with the drain flies persistence.

She tried using a strong bleach cleaner, but the flies returned the next day, as she’d heard from others in a similar predicament.

Finally, a friend suggested pouring a 2.5-litre container of bleach down the drains to eliminate the flies within 24 hours, but the flies remained even after Lynette followed this advice.

Identifying drain flies in your home

Drain flies can be unsightly and frustrating, but they pose no health or property damage risks. They don’t bite or transmit diseases, nor do they ruin clothes, towels, or linen.

The problem lies in their ability to breed quickly, causing frustration for homeowners like Lynette. Unfortunately, the more she killed, the more seemed to emerge.

The flies are small, at only 3-4mm in length, with dark grey bodies and hairy moth-like wings that dominate their body size, as shown in the photo below.

Solving the mystery of why drain flies only appear in bathrooms?

If you’re not on an acreage with a septic tank or sewer treatment plant, your only encounter with these annoying flies is probably in your bathroom. These flies are prolific breeders in septic tanks and treatment plants but tend to stay near their food source.

During the day, bathroom flies often sit on walls or under the vanity basin or ceiling. However, they are more active at night, so you may not see them flying or emerging from your floor waste drain.

Despite being poor fliers, drain flies can travel long distances of 3-5km, carried by the wind away from septic tanks or treatment plants. They can enter your home through your insect screens since they are small enough to fit through the holes in the mesh. Ultimately, they will seek out your bathroom floor waste drains as a food and breeding source.

The drain fly dilemma where do they live and breed?

Drain flies are weak fliers, never straying far from the bathroom floor waste drain, causing them to be exclusively found in bathrooms.

Infestations occur when temperatures exceed 20°C in spring. Drain flies multiply rapidly as their life cycle is 1-3 weeks from egg to adult. Eggs hatch within 48 hours, becoming larvae that mature within 12 days, feeding on decaying organic matter in the bathroom floor waste drain. The adult flies emerge from the drain at night, living no more than two weeks.

Tiny insects, big headache: Tips for eliminating drain flies from your​ bathroom?

Removing breeding sites in bathroom drains is the best way to control and eliminate drain flies. Bleach can help with minor infestations but not major ones, which require sealing and cleaning of the floor waste trap.

Our experience has shown that cleaning the area around the floor waste, and inside the drain, with Enzyme Wizard All Purpose Surface Spray will sanitise and disinfect the breeding ground and food source of drain flies.

If you’re struggling with persistent drain fly infestations, call us at Whywait Plumbing on (07) 5580 4311 to book a service call. We’ll eliminate them for good.