Drain Flies 101: What You Need to Know About These Pesky Household Pests

by Derrick | Last Updated: February 23, 2023

Drain flies, sometimes called moth flies or sink flies, are a common household pest found in many parts of the world. Growing to a size of around 2mm – 5mm, they look similar to gnats and fruit flies, but with their round, fuzzy bodies and small moth-like wings, they can easily be recognized. They come in several shades ranging from pale grey to black, which generally distinguishes them from other similar flies. Unfortunately, drain flies only have limited flying ability, so they tend to jump from one place to another instead of buzzing around as you would expect them to do.

Living an average lifespan between 8-24 days, it is important that homeowners take action quickly if they suspect these pests in their house because female drain flies will lay up to 300 eggs after 48 hours! If left untreated for too long, the problem can become more severe over time as those new larvae mature, and the cycle continues until something is done about it. Equipped with all the knowledge you now have about what drain flies are, make sure you understand the signs of an infestation so that you can identify and prevent any problems before it gets too out of hand!

What Causes Drain Flies?

Drains are a perfect breeding ground for pesky drain flies. These annoying insects thrive in environments with stagnant, shallow water and debris, making it the ideal habitat. Areas such as sinks, showers, basement or workshop sinks are often hot spots for drain fly populations due to limited flow of air movement and cleaning. Drain flies even have adapted to be able to survive in relatively clean areas by using the bacteria and food particles that stick to sides of pipes or any other bit of organic material they can find.

Outside sources may also play a role in causing a rise of drain fly population over time. Long absences from home (like on vacation) may provide an opportunity for the eggs lying dormant in organic bits in drains to hatch more readily without disturbing vibrations from daily activities. If simple preventative maintenance like checking shower and sink drains regularly is not done, then colonies of these small pests will continue to form until either pest control is employed or a deep clean remove eggs and build-up alike is performed.

How Do You Know If You Have Drain Flies?

If you suspect your household has drain flies present, there are a few ways to tell for sure. If you’re lucky enough to spot one or two in the process of their annoying buzzing noise, try an overnight test: Place pieces of tape (sticky side down) over the drain in question, as this will help trap any potential escapees as they try to escape. This will indicate how many flies could be lurking around the drain afterwards – and this number can also tell you just how severe the infestation is. If more than a couple of them appear on the tape, there likely are more hiding out of sight in other areas of your home – making draining cleaning and possibly professional pest management services necessary.

Are Drain Flies Harmful or Dangerous To Humans?

Drain flies are not harmful to humans but can be a nuisance if their numbers become too large. Similar to fruit flies, they are mostly an annoying nuisance that can be a challenge to get rid of.

At the same time, however, research has shown that infestations of drain flies can trigger asthmatic reactions in some people due to particles released from the insect’s wings during flight, which may cause allergies or aggravate respiratory issues. Additionally, myiasis is a rare but serious disease caused by fly larvae growing inside humans or other animals – including squirrels, rabbits and foxes – after they have been laid on the skin, usually through an open wound or sore. While this condition is very unlikely to be transmitted by drain flies, health professionals still advised homeowners to use extreme caution if they suspect an infestation near their property.

Control Measures For Drain Flies

Control measures should focus on eliminating their breeding sites in drains such as floors, sinks, wash basins and bathtubs. It may take persistent effort to achieve this goal since the larvae are often hidden deep in the drains and hard to reach.

It is possible that the source of an infestation comes from an external source, such as a nearby filter plant or commercial cooling tower or from regularly irrigated or wet mulch lying around a building. In this case, control measures should be focused as much on reducing access to these sources as on cleaning out any affected drains. 

Identifying the breeding site is essential. Because of their small size, they are often hard to spot, but common breeding sites can be found around drains in floors, sinks, wash basins, bathtubs and more. Eliminating the larval breeding sites is vital to getting rid of the infestation; all areas that could potentially serve as a source of food or shelter need to be thoroughly cleaned and sealed off.

A standard control plan should entail:


  1. Clean your drains regularly: Use a drain cleaner to remove any buildup of organic matter and debris that could serve as a food source for drain flies.
  2. Keep your drains dry: After using sinks or showers, wipe down the drains with a dry towel to remove any moisture. This will help prevent drain flies from laying their eggs in the moist environment.
  3. Fix any leaks: Check for and fix any leaks in your plumbing system, as these can create moist environments that are ideal for drain flies.
  4. Seal any cracks: Check for and seal any cracks or gaps in your walls, floors, and foundation that could allow drain flies to enter your home.
  5. Keep your garbage cans clean: Make sure your garbage cans are kept clean and free of food debris, as this can attract drain flies.
  6. Use fly traps: Place sticky traps near drains and other areas where drain flies are commonly found to help control their population.

Following these steps can significantly reduce the likelihood of a drain fly infestation in your home.

Pesticide or Chemical Treatments

Several types of pesticide or chemical treatments can be used to control drain flies. Some common treatments include:

  1. Biological drain cleaners: These contain enzymes or bacteria that break down the organic matter in drains, eliminating the food source for drain flies.
  2. Insecticide sprays: These can be sprayed directly into drains or around areas where drain flies are present to kill them. However, they are less effective than other treatments because drain flies may resist them.
  3. IGRs (Insect Growth Regulators): These are chemicals that prevent the development of drain fly larvae into adults, thus breaking the breeding cycle.
  4. Pyrethrin-based aerosols: These are insecticides that can be sprayed in the air to kill adult drain flies.
  5. Smoke bombs/foggers: These products release a fog or smoke that penetrates into drains and other areas where drain flies hide, killing them.

It is important to note that while these treatments can be effective in controlling drain flies, they should be used carefully and according to the manufacturer’s instructions to ensure the safety of people and pets. It is also recommended to seek the help of a pest control professional for severe infestations.

Follow-up Inspections

After treating an infestation of drain flies, it’s important to conduct follow-up inspections to ensure that the problem has been resolved and to prevent re-infestation. Here are some steps you can take for follow-up inspections:

  1. Check the drains: After treatment, check the drains where the drain flies were previously found to ensure that there are no new signs of activity.
  2. Check other moist areas: Check other moist areas in your home, such as sink traps, shower drains, and garbage disposals, to ensure that drain flies are not present.
  3. Clean the drains regularly: Even after the infestation has been resolved, it’s important to continue cleaning your drains regularly to prevent a recurrence.
  4. Fix any leaks: Check for and fix any leaks in your plumbing system that could create moist environments that are ideal for drain flies.
  5. Monitor fly traps: If you’re using fly traps, monitor them regularly to ensure that they’re still effective in controlling drain flies.
  6. Seek professional help: If the infestation persists or reoccurs, it may be necessary to seek the help of a pest control professional.

By conducting regular inspections and taking preventative measures, you can help ensure that your home remains free of drain flies.

Wrapping Up

In conclusion, drain flies are a common household pest that thrive in stagnant, shallow water and debris. They can be recognized by their round, fuzzy bodies and small moth-like wings and are often found in drains in areas such as sinks, showers, and basements. While they are not harmful to humans, they can be a nuisance, and their infestation can trigger asthmatic reactions in some people.

Prevention measures include regular cleaning of drains, keeping drains dry, fixing leaks, sealing cracks, and cleaning garbage cans.

If an infestation is suspected, identifying the breeding site is essential, and all areas that could serve as food or shelter should be thoroughly cleaned and sealed off. By following these steps, homeowners can control the drain fly population and prevent a severe infestation from occurring.