A dishwasher is essentially a watertight box that sprays dishes with hot water and soap, drains out the dirty water, and then dries the dishes.

Hot water is delivered through a supply hose to a valve that controls the water's distribution to spinning spray arms. A pump gets rid of the dirty water, and an electric heating element dries the dishes. All of this is operated by controls that may be very simple or quite complex.

When working on a dishwasher, follow a few important precautions. Always unplug it before working on it. Turn off the hot water supply valve (usually located under the sink) before disconnecting any hoses or working on the supply valve. And don't work on the dishwasher just after it's finished washing—some parts, particularly the heating elements, may be very hot.

How Hard is Your Water?
Contact your local utility to find out how many grains of hardness your water has. When operating the machine, use the right amount of soap for your water type—1 teaspoon per grain of water hardness.