Water helps move food around in the garbage disposal grinding chamber. It also helps to flush the food and debris down the drain once it’s finely ground. When you are grinding food in the disposal, use cold water. This keeps any fat and oil in its solid form, so it gets ground up and not sent down the drain as a liquid, only to harden and clog things up later on. However, you should use hot water if you are running the disposal to clean it.