Microbe Drain Magic clears clogged drains as well as eliminates drain flies. This product is used by funneling the hose into the drain and releasing the foam. Hold down the applicator until the foam is coming out the top of the drain. Allow the foam to turn into a liquid. This process takes about 30 minutes. As the foam is turning into a liquid it begins to eat away at bacteria and flushes the debris away. The debris is also the environment which allows Drain Flies to thrive. This product then has a dual purpose. It is easy to use and very effective.