There are chemical and non-chemical solutions available to kill drain flies, however the long term success rate of killing drain flies depends on how well one maintains a preventative routine. Drain flies are born, breed, and feed on decaying organic matter and in order to kill and eradicate these pests, the source of their breeding grounds must be destroyed.
- Create a trap for the drain flies and sett it near the suspected breeding grounds. One method recommends filling a shallow pie pan or a medium sized Mason jar with equal parts of sugar, white vinegar, and water. Add several drops of liquid dish soap. The flies will be drawn to the sweet smell of the sugar and white vinegar, but will drown once they land on the soap laced water. This method is effective for killing existing adult drain flies, but will not kill drain flies in the egg, larvae, or pupae stages.
- Using a pipe brush and a plumbing snake that is at least seven feet long, remove the built up residue of soap scum, hair, and grease. This will be a messy and unpleasant job. Have a trash bag on hand to dump your drain findings. Many are surprised when they pull out a foot long hair clump, but without regular cleanings, these things have a way of happening.
- Following the pipe cleaning, run a bit of fresh water through the pipes. Shut off the water and tightly fit a sturdy plunger over the open mouth of the drain. If you are working on a double sided sink, counter pressure will have be applied to the other opening. Plug the drain with a fitted rubber stopper and ask an assistant to press firmly on the plug so it will not shoot out. Thrust the plunger forcefully several times, expelling any water or organic material which may be adhering to the pipe walls.
- When finished plunging, pour a large pot of boiled water down the drain. This will sweep away any remaining debris disturbed by the plunger.
Chemical Solutions – DF 5000 drain cleaner
There are a number of products made specifically for controlling drain flies by destroying their breeding grounds. DF 5000 Drain Gel is a super thick gel that’s designed to be poured down drains. It uses bacteria cultures and enzymes to break down that lovely organic stuff that drain flies like so much. Drain Gel uses bacillus spores and works the same way. Similarly, Invade Bio Drain Gel uses microbes and citrus oil. Invade Hot Spot is a spray foam that also uses microbes and citrus oil and is good for floor drains and around drain pipes. If you’re looking for something to kill the adult drain flies before you start working, Invader HPX (active ingredient propoxur) is worth looking into.
Bleach will not do the trick as it only kills bacteria, not insects.