1. Clean - Pour 1/2 cup of baking soda down the drain, follow with 1 cup of white vinegar. Let this sit for about 5 minutes, do work it's magic. Boil a pot of water while waiting, then pour it down the drain. This will help to remove and kill any mold or bacterial building up in the pipe.
2. Fresh Smell - Pour 1 cup of ice down the drain (this also helps to clean off the blades). Include some lemon, orange, grapefruit or lime rinds to the ice; for the clean smell. Then turn on the blades as they chop up the ice and rinds they will help to clean and leave a fresh scent in your kitchen area.
This is a process that can be repeated as often as you feel necessary.
