Why drain flies keep coming back

Drain fly also known as moth fly

As their name implies, drain flies usually infest sewer pipes. Hence, they can be found in kitchens and bathrooms, where they tend to gather on walls and the floor, creating disturbances for the household. Several species of such pests are known, and it is difficult for a non-specialist to distinguish them, so a consultation with a professional is essential in developing an adequate strategy for eliminating them once and for all.

Know your enemy

The issue with drain flies, no wonder, is rooted in not enough drain maintenance and cleaning: pipes get clogged with organic materials that give pests a place to feed and breed. Drain flies get into houses through windows, basements, and sewers to then lay eggs in that decomposing organic goo. When the infestation takes place, another generation of flies develops in a period of two to three weeks and repeats the cycle.

Meanwhile, the drain fly larvae are known to be extremely hard to kill: they can survive substantial temperature changes and persist in low-oxygen environments — this is why drain flies keep coming back even after pouring boiling water down the drain. Another ineffective way to get rid of drain flies is bleach: while the chemical will remove some drain fly eggs and larvae, it will still pass down the drain too quickly to eliminate the entire nest. Moreover, bleach can damage the plumbing, as it is a corrosive liquid.

So, how to get rid of drain flies for good?

A highly effective control measure in ensuring that drain flies are gone is removing their breeding spot. Once the larvae and the flies have no feeding sources, they die out. Spring clog removers and long-handled brushes are quite helpful when removing decaying materials from the drain. Drain sides are often covered in a gelatinous film that requires cleaning as well. When the site is found and cleaned, the adult flies will live up to 20 days, but they will have no place to lay eggs, and no new flies will emerge from the drain.

a drain fly on the wall
sewer fly on the wall

If drain flies keep coming back, there is a possibility that there is another infestation site. Other pumps, drains, and sinks should be thoroughly checked to discover secondary infestation and handle it too. Sometimes larvae can be spotted right away at the drain opening, but that’s not universal, as eggs could be laid deeper within the pipe.

In addition to pipes, drain flies can breed in other places with moisture, standing water, and rotting organics. Wet buckets and mops, storm drains, recycle bins — these are just a few suggestions for the places to check.

Considering how much time and effort it takes to eradicate drain flies, the better option would be to contact pest control professionals: they can identify pests correctly and elaborate an efficient and safe strategy for managing them that would suit each unique case.

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