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.
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 like to stay near drains where they lay their eggs and feed on microorganisms and liquid carbohydrates found in the slime that builds up over time. Though they generally behave very sedately, they react quite quickly when threatened with water.
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.
Once you've wiped out their breeding ground, the adults will eventually disappear because there is nowhere left for them to deposit their eggs.
Most exterminators use chemical methods and habitat modification to kill all eggs, larvae, and adult drain flies (removing food sources, etc.).
Check for Larvae
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.
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.
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. Drain flies breed in areas that are moist and have a lot of organic remains, including: Sinks.
One common remedy for killing drain flies is using household bleach. This is a very useful and cost-effective manner for getting rid of these little pests with an item you already have around the house.
Essential oils are sometimes used to keep flies away from infested sections and also to kill them. Lavender, eucalyptus, peppermint, lemongrass, and citronella are just a few of the scents that insects despise (with lavender probably being the most effective).
While this chemical might get rid of some larvae, bleach passes quickly down the drain and does not penetrate the thick build-up where eggs are deposited by the female drain fly and larvae live. As a result, in most cases, bleach does not get rid of drain flies.
Drain flies gather, mate, and lay eggs in moisture or standing water. The slimy film that forms in sewers and drains is a favorite breeding spot. Putting off regular cleaning and maintenance of these areas may attract the pests and offer them a place to feed and develop.
Some species hold the wings out to the side, which gives them a moth-like appearance—hence the name "moth fly." They are weak fliers and make irregular, hesitating flights covering only a few feet in short, jerky lines. Eggs are tiny, brown or cream-colored and are laid in irregular masses of 10 to 200.
Drain flies may keep coming back due to poorly executed or ignored mechanical cleaning; failure to eliminate all breeding grounds, surviving eggs, and larvae; and failure to conduct regular cleaning and maintenance of the drain pipes. Adult flies can continue to get in from outside, so seal all possible entry points.
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.
One possible sign of an undetected mold problem in your home or office could be the presence of Phorid flies, sewer flies or some other gnats or bugs.
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.
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.
These pests live and breed inside your plumbing pipes, feeding on decomposing material and laying eggs within the gelatinous slime that collects along the interior walls of your drain. Adults can be spotted resting on walls and ceilings of the infested areas.
Adult flies emerge from the breeding sites but may remain nearby. Drain fly control often fails because people don't realize just how resistant the scum and the larvae are to boiling water, bleach, detergent, and even caustic drain cleaners (see How Can I Get Rid of Drain Flies?).
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.