When you see new pests in your house, your first reaction is disgust, quickly followed by How do I get rid of these things—fast? And then, probably something like How can I keep this from ever happening again?
Here's how to prevent the infestation of one such tiny intruder, the drain fly.
Drain flies live—appropriately to their name—in drains, sewers, septic tanks, and soil contaminated with sewage. They feed on the organic matter within the pipes and, if given just the right set of circumstances and opportunities, will come through access points like kitchen sinks and shower drains right into your home.
They're harmless and won't bite or sting, but since they arrive in large numbers they can be quite a nuisance.
How Do You Know if You Have Drain Flies?
You'll usually spot them as a small infestation near the access point—resting on the walls near a shower or hovering inside a sink. Specifically, you're likely to spot drain flies near sinks and showers that are stagnant for a time (like after a long vacation) or used very infrequently (such as a guest bathroom).
Drain flies are small—measuring an eighth of an inch, which is about the size of a fruit fly or a gnat (it's easy to confuse them, as a matter of fact). Drain flies are gray or brown in color with light-colored wings, and can leave behind a powdery substance when they are crushed. Drain flies are also fuzzy—covered in hair on their body and wings to give them a furry appearance. They can be identified by the unique pattern of veins on their wings and their erratic flying pattern.
If you see flies matching this description in your kitchen or bathroom, they could be drain flies (but be sure to check for other sources as well, such as rotting fruit, which could suggest that you're dealing with a different pest).
How to Get Rid of Drain Flies
To identify where the drain flies are coming into your home, cover any suspected access points with clear packing tape. This should stop new flies from coming inside, but also trap any on the tape as they're trying to come into your home.
You can eliminate the flies already inside with a quick trap: Fill a bowl or jar with equal parts sugar, water and white vinegar, then add 5 to 10 drops of liquid dish soap. Leave the jar next to the sink or shower drain overnight or up to a week until the flies are gone.
Once you know where the drain flies are coming in, keep the access point covered with sticky tape or a drain plug at all times. Once or twice daily, boil a pot of water, uncover the drain and pour the boiling water down it. Recover the drain, and repeat the boiling water method once or twice daily for at least a week until the flies are gone.
How to Prevent Drain Flies
Since drain flies feed on organic matter within pipes, the first step of prevention is keeping drains clean and clear with proper pipe-cleaning maintenance, such as cleaning sinks and drains regularly with dish soap or vinegar and very hot water.
The One-Minute Habit That'll Keep Bathroom Pests Away
Besides cleaning regularly, the best thing you can do to prevent a drain fly infestation is to make sure that you do not have stagnant water sitting in your pipes. It can sit in the curves of rarely used pipes—like in that guest half bath that's almost never used. Ameliorating the effect of stagnant water is as simple as running the water in rarely used showers or drains for about a minute once a week. For good measure, add half a cup of salt and half a cup of baking soda to the drain and flush down with one cup of white vinegar.
To remember to do this, tie the task to something else that you do weekly, such as watering your plants or cleaning out the fridge. With good preventative measures and a little luck, you'll never have to actually identify drain flies or deal with them.