Why Do Drain Flies Appear in Summer?

Summer 2024 is here, and guess what? So are drain flies

drain fly sitting on a wall

A common nuisance in both residential and commercial settings, the drain fly, also known as sewer flies, can quickly ruin your summer joy.

There are a few reasons drains flies appear more often in the summer months. This includes expansion of breeding sites, additional food sources, better temperature and humidity and increased water sources. All of these elements create ideal conditions for infestation.

During summer, drain flies can breed outdoors in low, wet areas like air conditioning drain sites or clogged gutters, entering homes through open doors or windows. If you’ve looked high and low, and still cannot identify the source of infestation, check those areas, along with your potted plants.

The key to managing drain flies is thorough cleaning of these potential breeding sites.

Why Does the Drain Fly Population Increase in Summer?

people playing out side in the summer

Expansion of Breeding Sites

Summer weather contributes to quicker accumulation of stagnant water and organic material, creating more breeding grounds for drain flies. From floor drains and storm drains to plant pots, the increased number of potential habitats boosts the drain fly population.

AC window unit

It doesn’t take much for them to start breeding. They can lay up to 100 eggs which hatch in less than two days! This is why it’s easy for an infestation to get out of control quickly. 

Adults are not strong flyers, and do more a flying “hop”. Tracking them down is easy, but that’s only half the battle.

Proliferation of Food Sources

Drain flies feed on organic material. The bustling summer activity in kitchens and outdoor areas results in more food residues and decomposing matter, which become abundant food sources for these insects. This surplus of food and the accelerated decomposition caused by the warm weather support the growth of the drain fly population.

Favorable Temperature and Humidity

meter showing temperature

The life cycle of drain flies thrives in warm and humid conditions, characteristics of the summer months. These conditions enable drain fly eggs to hatch quicker, the larvae to grow faster, and eventually transform into adult flies at an increased pace. This faster breeding leads to a higher number of drain flies.

Increased Water Sources

Water is a vital survival element for drain flies. During summer, water usage increases due to activities such as plant watering, pool filling, and frequent outdoor gatherings. This heightened water availability offers drain flies more water sources, hence contributing to their larger presence.

How to Treat Drain Flies 

Controlling a drain fly infestation involves several steps that target both adult flies and their larvae. Here’s a comprehensive guide on how to get rid of drain flies.

Identify the Source

First, confirm that you’re dealing with drain flies and identify their breeding grounds. Drain flies are tiny, moth-like flies that are usually found near sinks, bathtubs, and other areas with stagnant water. They lay their eggs in the biofilm that forms in these wet areas.

Clean the Drains and Pipes

Long pipe brush for cleaning drains

Once you’ve identified the infested drains, clean them thoroughly. Use a long, stiff pipe brush or a plumber’s snake to scrub away the organic material that forms in the drain. This biofilm is where the drain fly larvae live and feed. Removing and preventing buildup is key to eliminating breeding grounds. Removing adults (the flies you see) will not solve the issue alone!

If you have a slow drain or complete blockage, you may need the services of a plumber. This also applies if you suspect a sewer line break under you home.

Drain Cleaners

After physically cleaning the drains, use a drain cleaner to ensure all the organic matter is removed. You can use chemical-based drain cleaners, or go for eco-friendly alternatives such as a mixture of baking soda and vinegar followed by boiling water.

bio drain gel goodbyedrainflies

Common favorites are Invade Bio Drain and Green Gobbler

Regular Drain Maintenance

Clogged drain being cleaned

Finally, make drain maintenance part of your regular cleaning routine. This means not only cleaning the surface of your drains but giving them a good, deep clean every so often to ensure no organic matter is building up inside.

Make sure to also check your sump pit or basement for fly activity.

In Summary

As summer rolls in, so do drain flies, turning up uninvited in our homes and businesses. Thanks to the warmer weather, breeding sites for these pests multiply, organic food sources become abundant, and the humid conditions speed up their life cycle.

Dog smiling outside in the summer

Meanwhile, our increased water usage provides just the kind of environment these bugs love. But there’s a strategy to tackle this issue: identify the source, usually near stagnant water, clean the drains thoroughly to destroy their breeding grounds, use drain cleaners like Invade Bio Drain or Green Gobbler to get rid of organic matter, and finally, keep up with regular drain maintenance. (Drano can also work.)

By maintaining clean and dry conditions, you can keep your home drain fly-free this summer.