Hot grease may pour easily down a drain, but when it cools, it solidifies and sticks to the sides of your pipe, reducing its diameter, slowing water pressure, and causing a bottleneck that encourages clogs. Other foreign materials like objects (jewelry, toys, etc. ) or pieces of food waste can also enter the drain and the pipes below, but will become trapped at the next bend in the plumbing. While some water will still drain through the pipe, the bottleneck and partial blockage will drastically slow down the drain.