Case Studies

Pests We Treat Case Studies: Drain Flies in Apartment - Fly Removal and Control Inselin, NJ

Tuesday, March 1st, 2016 by Tom Hayes


Cowleys Pest Services is responsible for hundreds of commercial accounts throughout New Jersey, including a wide range of apartment complexes of all sizes. One of our long-standing commercial accounts is an apartment complex located in Iselin, which is part of Woodbridge Township in Middlesex County. While performing a routine service call, I was notified by the property manager that a tenant was complaining of small flies in his bathroom. When a homeowner or tenant complains of a problem with small flies, the usual suspect is fruit flies. Although fruit flies can be active throughout the year indoors, they tend to be a problem mostly in the summer when their populations build. Fruit flies are usually found in the kitchen where exposed ripened fruits and vegetables are lying on counters or there is decaying fruit in trash cans or drains. However, since this fly infestation was in the bathroom, another potential pest came to my mind as I was on my way to the apartment unit: drain flies.

Upon inspecting the bathroom, my hunch was correct. This unit did indeed have a drain fly problem. Drain flies are small gnat-type flies that feed off and lay their eggs in the accumulated organic matter, or what I prefer to call “muck,” found inside moist drains. When the eggs hatch, the drain flies then shoot out of the drain. It’s not a pleasant sight. Drain flies are often reported in the kitchen, just like fruit flies, since the kitchen drain usually has the most accumulation of muck of any drain in the home. However, just like with this apartment unit, drain flies can also be found in shower drains. Shower drains can accumulate their fair share of organic matter. Soaps and shampoos are made with fats and oils, our hair is made of dead cells compressed to form keratin, which is a protein, and during a shower, we flake off dead skin from our scalp and body that winds up down the drain as well. All of this is plenty of food for drain flies.

Drain flies, also known as moth flies, sewer flies, or filter flies, are small true flies, about 1/8 inch, with short fuzzy bodies and oversized wings that gives them a "furry" moth-like appearance. They are black or brown and have noticeable veins in their wings. They breed in drains, sewers, septic tanks, and even soil that has been contaminated with sewage. Unfortunately, if you come across one, there’s a really good chance that a couple of hundred of his close relatives are either nearby or will be soon. Like fruit flies, they are small, hang out in groups, and elicit a strong feeling of disgust whenever we see them. Knowing the breeding habits and environs of these pesky creatures helps me eliminate these infestation quickly.

The bathroom of the apartment was at ground level, so I wanted to verify that there were no issues in the crawl space below. It was a good thing I did. Upon inspecting the crawl space, I found a broken water pipe from the tub that was leaking water into the crawl. This was not only another potential breeding ground for the drain flies, but the water intrusion could trigger a host of problems down the road. A damp crawl is not only an invitation for ants, termites, and other insects, but there is also the strong possibility of dangerous mold growth. Once mold forms in the crawl space, the spores can spread throughout the units, degrading air quality and potentially causing health risks to the tenants.


I informed the Superintendent and the Property Manager of my findings. If the apartment owner wishes to encapsulate the crawl space, Cowleys has a crawl space encapsulation division that permanently eliminates the ongoing problems of vented crawl spaces. Crawl space encapsulation has numerous benefits such a improving air quality, preventing wood damage from moisture, lowering energy bills, and preventing insect and wildlife infestations. We also have a Mold Solutions division that uses the patented products of the Mold Exterm system to treat mold through bioremediation should the apartment owner decide to have one of our mold representatives examine the crawl space for mold growth.

I was able to successfully resolve the drain fly problem that day, and the property manager was grateful that I located a serious water problem developing in the crawl space. Cowleys will follow up with its other services depending on how the owner wishes to address and treat the water intrusion problem in the crawl space.