The Dreary Life of Drain Flies

When many people hear the word “flies,” there are a few species that come to mind. While house flies, fruit flies, and horse flies are all commonly found across the country, there is another kind that plagues our homes: drain flies. These pests inhabit disposals and pipes, which would not be a noticeable problem if they didn’t erratically fly out of the drains like reverse bacteria-infested confetti. But why do drain flies like these disgusting locations in the first place? Let’s explore the short lives of these fluttery pests and why they could be signs of further plumbing issues.

The Life Cycle

Drain flies share a similar life cycle to other types of flies, including a comparatively short life span. These flies, also called moth flies, start out in uneven masses of 10 to 200 eggs. The eggs are brown or cream-colored, and are often too tiny to see from a distance. After one to two days, the eggs hatch and reveal the larval stage of drain flies that remain legless and gray for one to two weeks. These gray larvae are technically the most beneficial stage of drain flies, as they live off of the residue and waste that builds up on the inside of moist pipes. This excessive eating gives enough energy to their next stage, the pupal stage, where the drain flies are more idle for about 20 to 40 hours. The final life stage is adult, where the drain flies reach their final form and finish their life cycle, which takes about one to three weeks total. 

Adult drain flies are the pests that we see most often since they have the wings to carry them out of their hiding spots in sewers and pipes. They are gray and fuzzy, and are about 1/5 to 1/6 of an inch long. Drain flies live for about two weeks in this phase, only resting in damp and dark places. Their long wings are either held above themselves or out to the sides when resting, depending on the species. If a house has a drain fly problem that did not previously exist, it is often because the adult flies were carried from nearby sewers and sewage plants by the wind. Since the adults live off of flower nectar primarily, their resting places are where they pick up the bacteria that can stick to their wings. Drain flies can easily fly away when they are splashed by a bit of water, so they are surprisingly resilient for their weak flights and short life spans. Because of this, their survival hinges on the conditions of the damp and seedy places that they live throughout all life stages. 

Favorable Yet Unsanitary Conditions

Considering the fact that three out of four life stages require water, it makes sense why drain flies are almost always found near some form of moisture. They often reproduce at sewage plants because they have the food, water, and shelter they need to survive. Young drain flies eat decay, algae, and bacterial film found in the inside of tubings. Any amount of shallow water that is polluted in some way is appealing to drain flies, especially if there are spots of algae and organic bacteria floating throughout the water. Drain flies also love drain pipes and overflow pipes, as a whole family of flies can continue reproducing in these covered spots for generations. Other favorite outdoor locations include sewage disposals, septic tanks, and compost. There doesn’t have to be much water in order to satisfy the drain fly.

In short, any dark space that is moist and dirty is the drain fly’s idea of paradise. This is why it seems contradictory that they are attracted to lights, and are drawn to our homes when the warm lights are on in the evenings. But this trait is shared among various fly species, so it makes sense that drain flies would not be the exception. If the drain flies happen to make it inside the house, they will not stray far from the drain they now call home. This isn’t just because they like the conditions of the drain; it is also due to the fact that drain flies are notably weak fliers. Their flight patterns are erratic and short, and they will only do so when they are seeking new shelter or in danger. Two of the most common places they invade in a house are garbage disposals and toilet tanks. Both places make pests out of the drain flies when they flutter out of hiding to land on the door or wall nearby. But the worst feature of drain flies is not their strange flight patterns or noticeably fuzzy bodies; it is the bacteria that lives around them in their natural habitats. 

Dangerous Drain Flies 

The good news is that drain flies do not bite or carry full diseases. But that doesn’t mean they are completely harmless either. One of the primary ways that drain flies can cause problems for us is if they land on certain spaces in the home. Since they primarily live in pipes and sewage, drain flies pick up plenty of harmful pathogens that we don’t want anywhere near our homes. It should also be noted that drain flies resist bleach and bleach-based products, so these so-called solutions do not actually do much against these pests. The drains in our sinks and tubs are not the cleanest places anyway, but a drain fly landing on the food or drinks we leave on the counter can easily transfer all of the bacteria and dust from their bodies onto the surface. If you see drain flies landing on anything edible, it is now contaminated and should be thrown out immediately.

The other main issue with a drain fly invasion is the components of their bodies. They may look like cute, fuzzy flies, but that fuzz is exactly what can affect the residents of the home. The tiny hairs on these flies keep them from easily drowning in the pipes they inhabit, as they are relatively water-resistant in small quantities. If there are multiple adult drain flies in a home, especially if they die indoors, the dust and fragments on their bodies can cause health issues in people. Some have even developed symptoms of bronchial asthma from inhaling the dust on drain flies. Drain flies are mainly active at night, so they could spread from their shelter while everyone is sleeping. Even though they enjoy dirty spaces, drain flies can still invade a clean home if they find an entry point. In fact, many drain fly invasions begin when everyone in the home is gone for a few days, as the flies have time to establish their home in the idle drains and sinks in the meantime.

DIY Tips and Tricks

In the event of a minor drain fly invasion, there are some easy solutions you can use with supplies you already have at home! The first step is to determine if you actually have a drain fly problem and to find the specific place that they are reproducing. You can tell if the problem is stemming from a specific drain by leaving a sticky covering over the opening overnight. This can be a plastic container with glue traps inside, masking tape, or a plastic bag with some kind of sticky substance inside. If there are drain flies in that drain, you will find at least a few flies caught in your trap. There are specific enzyme cleaners that are made to rid drains of flies and residue, most of which are available at big box stores. It is better to act sooner than later when drain flies are inside, since they will only continue breeding if left alone.

The main goal in preventing drain flies is to break up the bacteria and residue inside the pipes. If there is nothing for their young to eat, the flies will have less of a reason to set up shop. The simplest and most common method people use is to pour boiling water down the drain once or twice a week, especially in warmer seasons. This flushes the pipes of grime and washes away any hidden flies all at once. It is also helpful to use a stiff, long handled brush in the drain if there is more buildup. The other side of these cleaning practices is that the presence of drain flies can indicate a need for certain repairs. There may be a leaky pipe, a hole in the screen door, or gaps in the exterior of the house. Check the pipes for any leaks, patch up any torn screens, and fill gaps with caulk and/or copper mesh. The best way to prevent any pest is to block potential entry points that would otherwise grant them easy access into your home, including the drains! 

Nobody Prevents Indoor Pests Like Green!

Whether fuzzy flies are emerging from your sink or rodents are nesting in your walls, Green Pest Services has the treatments to solve your pest problems! We understand the importance of a pest-free home all year, which is why our contracts are scheduled on a quarterly basis. Whether you are receiving preventative or responsive pest control, our team of experienced technicians will not leave any job unfinished. Our technicians begin each visit with a thorough inspection of the property to ensure that every pest issue will be addressed with the proper treatments and products. We only use eco-friendly treatments that both prevent and eliminate pests without endangering your family and pets, like traditional pesticides have the risk of doing over time. Contact us for a free quote and for more information on how we will keep your home pest-free, no matter the season!

Citations

Klass, C. (2016, January). Drain flies or moth flies. Cornell University – Insect Diagnostic Laboratory. Available at http://idl.entomology.cornell.edu/wp-content/uploads/Drain-Flies.pdf (Accessed on December 29, 2022).

Moth flies or drain flies. (n.d.). Michigan State University – Plant & Pest Diagnostics. Retrieved December 29, 2022, from https://www.canr.msu.edu/resources/moth-flies-or-drain-flies 

Sansone, C., Minzenmayer, R., & Drees, B.M. (n.d.). Drain flies. Texas A&M Extension Entomology. Available at https://extensionentomology.tamu.edu/publications/drain-flies/ (Accessed on December 29, 2022).

Shetlar, D. (2014, April 10). Drain flies (moth flies). Ohio State University – Ohioline. Available at https://ohioline.osu.edu/factsheet/ENT-41 (Accessed on December 29, 2022).