Drain flies frequently lay eggs in the organic material that builds up right at the opening of your drain. Remove the drain cover, scrape some of the slime off the sides, and look for thin, tube-like, drain-fly larvae.
Identifying the Source
For the plastic cup method, lightly coat the inside of the cup with vegetable oil or petroleum jelly then invert the cup over a drain where you suspect flies may live. Leave the cup in place for several days, but check it daily.
During the day, adults rest in shaded areas or on walls near plumbing fixtures and on the sides of showers and tubs. Most activity occurs during the evening when these flies are seen hovering about drains and sinks.
They can breed in compost bins as easily as they reproduce in drains. They will also establish nests in septic tanks and soil that has been soaked in sewage or debris.
To make an all-natural drain fly trap, fill a bowl with apple cider vinegar and cover it with plastic wrap. Punch small holes in the wrapping. The vinegar's smell will attract the drain flies, and the wrap will trap them inside the bowl.
Boil a medium-size pot of water once or twice per week, and pour down and around the drain. Another easy option uses baking soda: Combine 1/2 cup salt with 1/2 cup baking soda and 1 cup of vinegar, and pour down the drain. Leave overnight, and finish by pouring boiling water down the drain in the morning.
Most exterminators use chemical methods and habitat modification to kill all eggs, larvae, and adult drain flies (removing food sources, etc.).
Once you've wiped out their breeding ground, the adults will eventually disappear because there is nowhere left for them to deposit their eggs.
What Causes Drain Flies? Drain flies thrive in stagnant and standing water. Common sources include slow or clogged drains, rarely used and unused toilets, refrigerator drain pans, and standing water created by leaking pipes. They typically enter buildings through basements, windows, and drains.
What are the signs of a drain fly infestation? As with most flies, the most noticeable sign of drain flies are the adults. They typically are seen resting on the walls in bathrooms or near the breeding materials. Larvae also may be observed wriggling in the breeding material.
Drain flies are most commonly found in the bathroom, particularly in drains that have stagnant water or grime sitting in the pipes. Therefore, you'll probably find the small flies in the toilet, sink drain or shower.
Behavior: Drain flies are most active at night. They are weak flyers that make short hopping flights of a few feet when they are disturbed. Drain flies rest on surfaces with their wings held over their back like a roof. You'll usually find a drain fly close to its breeding ground.
Lavender, eucalyptus, peppermint, lemongrass, and citronella are just a few of the scents that insects despise (with lavender probably being the most effective). Pouring half or an entire cup of such essential oil onto a sponge or rag, then storing it in a small can, helps keep flies at bay.
A cup of household bleach is generally more than sufficient to kill most drain flies, and all you need to do is pour it down the affected drain.
For effective drain fly treatment, use three products: Forid Drain Gel Cleaner, Gentrol IGR Aerosol, and Pyrid. Forid is an organic microbial grease degrader that breaks down organic material and waste, which will eliminate their food sources and their breeding grounds.
Drain flies can breed outdoors during the summer with adults entering homes through open doors or windows. Low, wet areas where air conditioning units drain, or clogged guttering are excellent places for these insects to develop.
These flies will breed in any moist area that they can find. So if you are facing a drain fly infestation that you cannot figure it out, you may want to look deeper for the cause. The problem could be from a leaking pipe or drain under the sink or even a leaking pipe inside of your walls.
Besides inadequate control measures, another reason why you have drain flies present again could be because there was a secondary infestation in another site that was not discovered or treated. There may be other bathroom drains, or a floor drain, laundry room drain, or sump pump that are breeding flies.
Do Drain Flies Die in Winter. Most fly species cannot survive outside temperatures below 32°F (0°C). They die unless they find a warm and conducive place to overwinter, such as your home. Drain flies are one of the few insects that can tolerate cold weather conditions.
The larval stage of drain flies lasts up to 24 days, while the pupal stage lasts between 1 and 2 days at most. The larvae feed on bacteria, fungi, and other microorganisms that develop in the breeding medium in drains, standing water, and even sewage treatment beds.
Drain flies are small and gray. They do not bite, sting, or spread diseases, but their decaying bodies may cause allergic reactions. They can also spread bacteria from trash, decaying vegetables and fruits.
Make a natural cleaning/fly killer mixture.
Mix together 1/2 cup of salt, 1/2 cup baking soda and 1 cup of vinegar. Pour the mixture down the drain. Let sit overnight, then flush the drain with hot water in the morning. This should kill all flies and the organic material they've been feeding on.
They will not bite you, they are not aggressive, they do not even really stray to far from the breeding source. However, drain flies can indirectly affect your health and family. That decomposing organic matter, sewage, bacteria, microorganisms, and fungi, we spoke about earlier, can host some nasty organisms.
Pouring boiling water is quite risky as it might lead to a steam burn or scalding. Another thing to keep in mind is what type of material you are pouring in into. If you have a porcelain sink, it is likely to crack due to the heat. All in all, pouring boiling water down your drain will only cause issues down the road.