If you've owned a garbage disposal for a long time or just installed your first one, it's common to wonder if you should use hot or cold water when grinding food waste. For all disposers, we recommend using a cool or cold steady stream of water when the disposal is running.
While we recommend that you avoid putting any fats, oils, or grease (FOG) into your disposal, there is inevitably some fat in common food waste such as salad dressings and macaroni and cheese. By using cool water, any fat will remain solid as it passes through the disposal and your drain pipes.
If water usage is a concern, know that, on average, a disposer uses only about 1 gallon of water per person per day, or about the same as a toilet flush. This is typically less than 1% of a household’s total water use. And average disposer electrical use is 3-4 KWh per year, or less than 50¢ a year in most locales.
So just a helpful reminder, do the "cool" thing and use COLD water when running your garbage disposal.