You've probably been warned at some point in your life that pouring grease or oil down the drain is a bad idea. Everyone has their lazy days, though, and you've probably ignored this warning in favor of a quick cleanup. Pouring trace amounts of grease down the drain once, while not a good thing, probably won't cause any serious blockages in your pipes, but if you frequently dispose of cooking oil and other grease deposits in the sink, then you have a problem building in your pipes. Many people think that running hot water down the drain will keep grease from sticking, but unfortunately that's not entirely true. Oil may be going into your drain as a liquid but as it cools and trails through your pipes, it starts to solidify. When the grease has cooled, it often sticks to the surface of the pipes, eventually causing a buildup.