How does bleach get rid of gnats? ... Here's how it works: Bleach is a most effective method of removal for gnats that tend to congregate around drains. Whether it's your sink, bathtub, or shower drain, pouring a half cup of bleach down the drain should wipe them out.

Does bleach kill gnat?

If you notice gnats around your kitchen sink or bathtub, pour a cup of diluted bleach down the drains to kill the gnats.

What is the fastest way to get rid of gnats?