I had a fly problem in 2020. I've tried Drano, bleach (not at the same time as Drano), and boiling water. Nothing got rid of her! Then I was gone for six days, so the two bathroom sinks leaked and disappeared. Well, they reappeared about six weeks ago. You are so annoying! So I researched other remedies and found this product. After the first night, the number of these pests was significantly reduced. I use it every night, 1/2 cup in two main sink drains, a shower drain and a hall bathroom sink