Dishwasher

Dishwasher, kitchen appliance that automatically washes, rinses, and dries dishes and utensils. To operate a modern dishwasher, the user loads dirty dishes into the machine’s wire racks, adds detergent, closes the loading door, and turns on the machine. A timer then opens a valve in the back of the dishwasher, filling the bottom of the machine’s interior, or tub, with hot water. When the water reaches a certain level, the timer activates a pump that forces water from the tub through spray arms mounted above and below the dish racks. The spray arms shoot jets of water at a rate of about 200 liters (about 50 gallons) per minute. At the same time, detergent is released from a receptacle, which is usually located on the inside of the door.

When the wash cycle is completed, the pump reverses, draining the tub into the household sewage system. The tub then fills with fresh water for the rinse cycle, during which the spray arms shower the dishes once again. When the wash and rinse cycles are complete, the timer begins the drying cycle by opening an air vent in the front of the door to expel hot air. The timer may also engage an electric heating element inside the tub. Heat radiating from the element raises the temperature and speeds the drying process.

Modern dishwashers offer a choice of wash and rinse cycles. Settings for cleaning large pots and pans, for example, may use two or more rinse cycles before the main wash cycle. Other settings are designed to conserve water and energy by limiting rinse cycles or bypassing the heating element in favor of simple air drying.

The first patent for a dishwasher was granted in 1850 to Joel Houghton of Ogden, New York. His wooden machine used a hand-turned wheel that splashed water on dishes. A more successful design was introduced at the 1893 Chicago World’s Fair by Josephine Cochrane of Shelbyville, Indiana. She originally built the dishwasher for her own use and went on to found a company based on the idea. That company later became KitchenAid. The first motor-powered dishwasher was developed in 1911.

Early dishwashers were slow to gain popularity as household appliances because the water had to be filled and emptied by hand, making them difficult to operate. A key improvement, introduced during the 1920s, was a dishwasher that permanently attached to household plumbing. By the 1940s, dishwashers were fully automatic and capable of electric drying. The late 1960s saw the introduction of dishwashers designed to fit conveniently under kitchen counters. During the 1980s quiet-operation and energy-saving features were added. With each new improvement the dishwasher has increased in popularity.