Drain flies don't bite, but still present a potentially serious health risk and should not be tolerated at home, work, school, or anywhere else. Drain flies don't transmit human diseases, but they can carry bacteria from their feeding and breeding grounds to food and surfaces that come in contact with food.

What Are Drain Flies?

Drain flies, also known as moth flies, resemble miniature moths- they look furry. Drain flies might look like fruit flies at 1/8 inch in length, but they have a hump-backed shape and do not have red eye color. Drain flies also have erratic flight patterns and tend to run across surfaces when disturbed as opposed to flying away (like most flies).

The life cycle of a drain fly is two to four weeks from egg to adult; and adult drain flies live about one to two weeks. A moist environment is needed for eggs, and the warmer an environment, the faster flies hatch and grow. An adult female drain fly will produce about 500 eggs in its lifecycle.

A Nuisance In A Home

Even though drain flies do not bite or carry any disease, they can become a nuisance especially if they are present in large numbers. With a large population, it would require a continual effort to eradicate any infestation in a home. Thus, it is best to control the condition starting by eliminating the breeding sites of the flies from sinks, wash basins, drains in the floor and even bathtubs.

Drain Fly Larvae

Drain pipes present a food source and breeding ground for drain flies. Flies lay eggs in their food source. Drain flies lay eggs in the gelatinous substance (or decomposing foods) found in drains. Drain flies will also use the slime found in the following areas for feeding and breeding sites:

  • Garbage disposals
  • Grease traps
  • Sewers
  • Toilets
  • Roof gutters
  • Potted plants
  • Garbage cans
  • Septic tanks

Drain Flies in Kitchens

Drain flies will even feed and breed in the decomposing organic material found in the cracks and crevices of floors in food preparation sites- like restaurants, kitchens and school cafeterias. Even the grim that builds up around the leg of a food preparation table and the restaurant kitchen floor could be a potential location for a female drain fly to lay eggs.

Drain Flies in Basements

Drain flies are also found in areas with mold. Mold is another food source and breeding ground for drain flies. Basements are the most common location for mold and drain flies, but crawl spaces, wall voids, and other wet areas with mold and fungus are a potential food source and breeding ground too.

Drain Flies and Slab Leaks

An underground leak, or slab leak, in a plumbing system can create the wet and/or moldy environment needed for drain flies to feed and reproduce. Mold is not required to create a food source and breeding ground- food stuffs and waste can travel to and accumulate at the leak location. So, drain flies could be an indicator of a plumbing leak!

Getting Rid of Drain Flies

You may detect if the moth flies are coming from the drain. This can be done by means of covering the opening of the drain during a down time with a glue board. You will need to keep the glue board over night or perhaps a few days allowing some time to catch the moth flies. If the flies indeed come from the drain then you should be able to catch a few flies on the trap that you have set up.

Cleaning Your Drain Pipes

Once it has been established that the flies indeed come from the drain, the next thing that needs to be done would be to clean the drain pipe or perhaps the traps to effectively eliminate the gelatinous rotting of organic matter sticking on the pipes. By doing this, you are eliminating the food source of the larvae. You can make use of a bacterial solution, which works quickly in dissolving the organic matter.

There are a lot of bacterial solutions available in local stores, which can help you achieve the task of cleaning out the rotting organic matter. Your best option is to ask your local plumber for advice regarding the best options. With such solutions, you may need to simply pour it around the drain and allow it to coat the sides of the drain. The treatment process would be done in 5 consecutive days. After such, this can be performed on a monthly basis.

Another option would be to manually scrub the gelatinous organic matter from the edges of the drain pipe. After which, you can flush the drain line with boiling water. Such home remedies don't always work and there could be bigger problems lurking, so consult with a professional licensed plumber.

If there are any leaks in your drain lines, it is best to seek a professional plumber to have this fixed as this can contribute to the problems with drain flies.

Cleaning the Other Sources of Moth Flies

A good way to increase the effectiveness of the task at hand would be to clean other sources of the moth flies. You should clean the dirty garbage containers and dispose your garbage properly. You might also want to check appliances and fixtures that make use of water. Check for wet areas or leaks as this can also serve as a breeding ground for moth flies.

Use Pesticides Cautiously

To eliminate the adult moth flies, you may use pesticides. However, when choosing a pesticide always make sure to check on the label to determine if this is organic and will not harm the environment. If you fail to do this, you may choose a harmful pesticide, which can do more damage than good for your health and the environment. You have to use caution when dealing with these substances.

Prevention and Control of Drain Flies

A fly swatter may take care of adult drain flies, but the only way to truely get rid of drain flies is to remove the breeding site. The larvae of moth flies can be controlled through eliminating the breeding sites by means of cleaning drain lines thoroughly. Aside from keeping drains, garbage disposals, grease traps, roof gutters, and other locations clean- clogs, overflows, leaks, and other moisture problems must be fixed.

Bleach, boiling water, and other "household remedies" are rarely effective. They help eliminate adult drain flies, but the eggs and breeding ground will likely survive. A hard cleaning with a brush is an option, but the most effective solution is professional help. Pest control specialists and plumbers have access to specialized drain cleaners for dealing with the slime drain flies feed and breed in. And if the problem is much larger- such as a slab leak or other plumbing problem, a plumber can help with leak detection, leak repair, septic system maintenance, and more.

The following items may help kill adult drain flies, but remember, eliminating the feeding and breeding ground is the only way to completely eliminate a drain fly infestation:

  • Fly swatter
  • Fly traps
  • Outdoor traps
  • Indoor electric traps (bug lights or bug zappers)
  • Non-insecticidal flypapers
  • Insecticidal insect sprays and pest strips

Eliminate the breeding site. It's the most sure-fire way to control and prevent drain flies. Drain cleaner alone won't remove the slime build-up. It must be brushed and cleaned out.

And if you do have drain flies, seriously considers calling your plumber, because you likely have a slow or clogged drain, and maybe even a plumbing leak.