Setting a bowl containing 1/2 cup of white vinegar on the top rack of a dishwasher and operating on the hottest setting is a natural way to sanitize a dishwasher. Sprinkling a cup of baking soda on the bottom of the machine and running a second cycle removes remaining odors.
Dishwashers spend a great deal of time cleaning dishes, and the grease and grime from the plates sometimes builds up on the dishwasher surface. The vinegar and hot water help to loosen the grease and dirt and allow the machine to pump it down the drain. Vinegar lowers the pH of the water, so it kills any bacteria that attach to the walls. For a dishwasher with plastic or enamel surfaces that are growing mold, running a cycle with chlorine bleach kills the mold, but consumers should not use bleach in dishwashers with stainless steel.
To prevent some of the dishwasher build-up, users should empty the garbage disposal before operating the dishwasher. Materials left in the disposal interfere with draining of the dishwasher, which allows dirty water from the disposal to siphon back into the bottom of the tub. The materials that travel back into the tub include bacteria and odors. They sometimes stain plastic tubs and cause a grease build-up.