Nine times out of ten, a drain fly problem will go away on its own. Once you get rid of the drain flies that you see, start flushing toilets and running the water in your sinks. This eliminates the standing water in which they dwell.
The good news is most drain fly issues can be fixed within about a week with regular cleaning and careful attention.
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.
One of the reasons that these types of critters — drain flies, in particular — are so difficult to get rid of is that they have water-repellant hair all over their bodies. Furthermore, the drain fly larvae are difficult to drown since “they are able to trap air bubbles and remain submerged for a day or more.”
So, the starting point would be to check the nearby drain pipes for infestations using the following methods: Duct tape test: Cover all the pipes with sticky tape. As flies try to come out of the drain, they will get stuck on the tape, giving proof of the source of the infestation.
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).
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.
Baking Soda, Boiling Water & Vinegar
The pour half a cup of bicarb soda down the sink as well, followed by a half cup of white vinegar. Let it settle for a few minutes then poor some more boiling water down the drain. Follows these steps every few days until the drain flies have completely disappeared.
Your Drain Pipe
As long as standing water is available, they will be able to reproduce. You may notice drain flies after being away for a while, or even after just a few days without using your sink—also watch out for flies regularly in drains that may not get a lot of use, like a guest room or basement.
Drain flies are typically only found in the summertime or in places with moderate year-round climates. Cold weather kills off more drain flies than any of their predators. If drain flies are able to find a home indoors, they can continue their development throughout the year, even during the winter.
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.
During the day, you'll notice drain flies resting on the wall since they aren't good fliers. At night, when they are active, they will congregate towards light sources, like lampshades. They will also feed and breed at night, so you'll see them near food sources or breeding areas.
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.
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.
Preventative Maintenance
Pouring bleach into the drain when the unit is not operating can leave residual bleach, which will damage the drain pan and line. Using vinegar for preventative maintenance throughout the year will keep your drain clean and clear and will not damage your line.
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. Inside structures, they are strongly attracted to light and will be found on glass windows, doors, lamps, and indoor lighting.
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.
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.
Create a fly and wasp repellent.
This DIY pest repellant should be a staple in the Southern home. Pour equal parts water and Pine-Sol in a spray bottle to spritz on outdoor furniture, the deck, and indoor areas where flies are most likely to flock to, such as kitchen countertops.
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. Another option is to mix a few drops of dish soap with a cup of vinegar.
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.
They reproduce in polluted, shallow water or highly moist organic solids where they feed on decaying organic material in mud, moss or water. In homes, the adult flies are most likely found on the walls of the bathrooms, kitchens, basements and other locations where sewer drains and plumbing fixtures are located.