How Do I Get Rid Of Drain Flies?


Drain flies or moth flies are a common problem in most households. That said, they can be rather frustrating to have in your home, especially if you have an infestation on your hands.

How do I get rid of drain flies? The first thing you should do when you notice a drain fly infestation is to get rid of all their breeding spaces. Second, focus on killing the adult drain flies. Doing both these things will help you get rid of the drain flies in all their life stages. This will reduce the risk of a second wave of infestation from happening. 

Drain flies are very resilient. Commonly found in kitchens and bathrooms, they feed and breed on the organic matter found in moist drains. The good news is that it is possible to completely get rid of them. This article will cover the most effective methods of getting rid of a drain fly infestation.

Signs of Infestation

Knowing how to identify areas that are infested with drain flies is an important step in knowing how to get rid of them. There are two common methods you could use to find out if you have a drain fly problem:

1. Spotting Drain Flies

This method involves finding the drain flies with your naked eye. This is a simple way of finding them in infested areas. If the area is infested, you will see adult drain flies perched on the walls or ceilings. Drain flies are poor at flying, hence they do not wander very far from their breeding area.

For instance, when you spot a drain fly close to a drain or a nearby pipe, chances are that the drain or the pipe are the breeding grounds for the flies. In case the infested area has multiple drains or pipes, you may have to resort to the drain test to identify the actual breeding ground.  

2. Drain Test

The drain test involves covering all the pipes and drainage outlets with sticky tape. The flies will then be trapped on the tape while trying to come out of the source, allowing you to pin-point the infested areas. The drain test is conducted using the following steps:

  • Clean all the drainage areas in the kitchen and the bathroom
  • Place clear tape over the drainage pipes and other outlets, with the sticky side facing downwards. This should be done at night as drain flies are nocturnal. The outlets should not be completely to allow them to come out of the drain
  • The trap should be left overnight or throughout the weekend
  • Remove the tape and inspect for any drain flies trapped on the tape

If you find flies trapped on the tape, the drainage outlet is a breeding source. If you do not find any flies trapped, repeat the test for at least four more nights to make up for differences in the breeding cycle. 

How to get rid of Drain Flies

Getting rid of a drain fly infestation is often difficult because most people are not aware of just how resistant they are. The wings of adult drain flies are coated with extremely fine water-repellent hairs, making them difficult to drown. They are also unaffected by most water-borne toxins such as aerosols.

Their eggs are also highly resistant to thermal and chemical assault. As a result, they are hardly affected by boiling water. The eggs can also withstand dehydration for an extended period.

The larvae attach themselves to surfaces using appendages on their ventral sides. They are also known to be able to withstand conditions with low oxygen. This makes it possible for the larvae to survive most assault measures.

Apart from inadequate control measures, another reason why your house may get re-infested with drain flies is the fact that there may have been a secondary infestation in the house that was not found or treated,

The secondary infestation may have been in the floor drain, bathroom drains, or the laundry room drain. You should also consider the fact that drain flies can breed in many other sites containing rotting, overripe, or decaying semi liquid organic sludge.

Examples of these areas include dirty recycling bins or garbage cans, drip pans that are placed under home appliances, stagnant water in a bucket, or potted plant saucers. 

While getting rid of drain flies, it is important to deal with them in all stages of their life cycle. This will help you get rid of the infestation faster, before it spreads further. The process of getting rid of drain flies occurs in two stages:

1. Get rid of the breeding source  

Once you identify the breeding ground of the drain flies, you can then get rid of all the dirt and slime present in the drains where they breed. Start by cleaning the drain from outside. You then moisten the drain by pouring warm water.

Once you have done this, use a metal brush to clean the drain. Do this by pushing the brush up and down the pipe. You can also clean the pipe using a plumbing snake to remove the grime.

After this, pour a drain cleaner gel into the drainage pipe. The gel coats the sides of the pipe. The purpose of the drain cleaner gel is to get rid of any organic matter present on the pipes.

In case you are unable to access drain cleaner gel, you could use boiling water and bleach. It should, however, be noted that boiling water and bleach are not effective since drain flies are resistant and can withstand high temperature.

After applying the drain cleaner gel to the drainage pipes, wait a few hours and then pour plenty of water. You can then use a plunger to get rid of any organic matter that may have remained in the pipe.  

2. Get rid of adult drain flies

Once you have gotten rid of the eggs and larvae, you can then deal with the adult drain flies. By cleaning out the drainage pipes, you will have gotten rid of their breeding grounds. Killing the adult flies next will solve the drain fly problem.  The methods used to kill adult drain flies include:

  • Using chemical sprays. The problem with chemical sprays, however, is that they are toxic. This makes the use of chemical sprays unsuitable in areas such as the kitchen.
  • Using a mechanical fly swatter. Adult drain flies are often seen on walls, making them easy targets. Once you have swatted them, clean up the mess on your walls using damp cloth.
  • Using soap spray. Most soap brands contain borax which possesses insecticidal properties. Spraying a mixture of warm water and dish soap on the flies kills them.
  • Using traps to trap drain flies in areas such as the kitchen. A simple trap is made by mixing equal amounts of water, sugar and white vinegar together with several drops of dish soap in a bowl. Set the bowl close to the kitchen sink and leave it overnight. The flies will be attracted by the sweet fragrance of the mixture, only to drown the moment they land on it. 

Life Cycle of a Drain Fly

Like all fly species, drain flies undergo a complete metamorphosis. They develop from an egg, pupa, larva, and eventually to an adult. Knowing the life stages of a drain fly and its appearance in each stage is important as you will be able to identify a drain fly infestation at any stage. This is important as the information may help you get rid of the infestation while it is in its early stages.

Typically, the life cycle of a drain fly is completed in 21 to 27 days. The speed at which the cycle is completed depends on the surrounding temperature. The cycle accelerates at higher temperatures.

1. Egg

Female drain flies can lay up to 100 eggs at once, but masses of 20-40 eggs are the most common. They lay the eggs on moist surfaces such as sides of drains and wet soil. They do not lay eggs on dry surfaces. The eggs are transparent and tiny, measuring less than 1 mm. The eggs take less than two days to hatch.

2. Larva

Once they hatch, the drain flies enter the larval stage. This is the longest stage of the cycle, lasting around 9 to 15 days. The larva has a slender body and is white or creamy brown in color. The body measures between 4 and 5 mm. The larvae feed on organic matter such as decaying vegetation, sediment, and microscopic animals and plants.

3. Pupa

Once the larvae have gathered energy, the pupal stage begins. The pupae are yellow to brown in color. Drain fly pupae are characterized by their horn-like respiratory features protruding from their heads. The pupal stage lasts between 24 and 48 hours. During this stage, the drain fly does not feed, and stays submerged close to the water surface. The drain fly then emerges an adult. It is also important to note that in temperatures below seven degrees Celsius, the pupal stage does not occur.   

4. Adult

Adult drain flies are smaller than the larvae, measuring about 1/8th of an inch. They have a mottled appearance characterized by dense and short hair-like scales found on their wings. This is the key feature used in the identification of adult drain flies.

Drain flies lack strong wing muscles and they maneuver mainly by running, hopping, or with short flights. When crushed, they leave behind a powdery smudge. They are typically nocturnal, meaning that they are most active by night. They appear to be attracted by odors around the house and light. They may also be seen during the day, often near illuminated surfaces and windows.

Adult drain flies live for approximately 20 days. They breed only once, usually within a few hours of emerging from their cocoons.  

How to prevent Re-infestation

To prevent a drain fly infestation from happening in your home again, you should ensure that your drains remain clean and free from clogging at all times. You should also get rid of any stagnant water present in your bathroom and kitchen, to eliminate all potential breeding spaces.

In addition, occasionally spray your drains with Insect Growth Regulator to prevent eggs from hatching, thus limiting the chances of infestation. 

Final Thoughts

Drain flies are relatively harmless to human beings. There are no known pathogens that they transmit. However, they can pose a real problem in case of a severe infestations. The bodies of dead drain flies may break down to form potential allergens. They can also be quite a nuisance when they land on people or fall into food.    

Luckily, drain flies do not bite. They do not sting either. They are nothing more than a nuisance. The dust they produce, however, can cause respiratory asthma in susceptible individuals.

Melanie Asiba

Melanie is an author. She enjoys traveling, reading and trying out new things. In addition to writing for Apartment ABC. Connect with her at [email protected]

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