Clean the dishwasher at least four times per year with a dishwashing cleansing product, or vinegar. Vinegar will break down the minerals, and remove the buildup on the walls of the dishwasher.
If you notice heavy scale and mineral deposits and have never cleaned your dishwasher, you may want to use a more powerful product than vinegar the first time. Just make sure the product is safe for dishwashers.
Vinegar should not harm your glass and plastic dishes and can be used with a load of dishes. Just fill a coffee mug with vinegar and place it, right side up, in the top rack with your load of dishes. The mug will overflow during the wash cycle and will clean all of the parts in the dishwasher.