How Do Dishwashers Work?

A dishwasher combines water with detergent, heats the mixture and sprays it against the dishes. It pumps out the dirty water and then rinses the dishes with clean water mixed with a rinse agent. After pumping out the rinse water, the dishes are dried by either heating or air drying them. The selector switch allows you to pick a variety of cycles which vary the length of wash, water temperature and drying temperature.

Dishwasher Operation

When the door latch is closed, the door switch is engaged and allows the dishwasher to operate. Based upon the chosen cycle, the selector switch signals the various components to operate at the appropriate stage of the cycle. The timer regulates the length of each stage of a cycle.

The water inlet valve fills the tub with water. A float in the tub prevents the dishwasher from overfilling. Either the float or the timer signals the inlet valve to close. The detergent is then released into the tub. In many dishwashers the mixture is heated with an electric heating element. Water that is not warm enough results in poor cleansing.

The motor turns a pump which forces the water up through the spray arms and spray tower (if any). The pressure of the water causes the arms to turn.

Dishwasher motors

Some dishwashers have a two-way motor. When it turns in one direction, it pumps the water through the spray arms. When it turns the other way, it pumps the water out through the drain. If the motor only turns in one direction, then an actuator moves to channel the water either to the spray arms or to the drain.

After the detergent cycle is complete the dishes are rinsed. If the dishwasher has a rinse agent feature, the rinse agent is added to the rinse water.

Once the rinse cycle has completed and the water has been pumped out, the dishes are dried. A electric heating element heats the interior of the dishwasher. Some dishwashers also have fan to circulate the air. A thermostat prevents the dishwasher from overheating.

Some dishwashers employ soil sensors to monitor the clarity of the wash water. When the water becomes clear, the sensor signals the control timer to advance to the next cycle.