Marjorie's right about the baking soda and vinegar. Pour about a 1/2 cup of baking soda down the drain, then give it a 1/2 cup chaser of vinegar. The resulting chemical reaction breaks fatty acids down into soap and glycerin, which is fantastic because it gives your pipes that eighteenth-century-homemade-soap freshness while it washes the clog down the drain. That being said---let's just not pour grease down the drain kids. It's better for everyone.