Drains clog every now and then, or at least slow down. I love flushing mine naturally. I pour about 1/2 cup of super washing soda into drain followed by about 2-3 cups vinegar (everything fizzes!), followed by a teakettle full of boiling hot water. This usually freshens the drain but if for some reason it didn't work, repeat until it does.
Whoohoo, #nontoxic!!!