How Dishwashers Work

On this page, I will explain how dishwashers work so that do-it-yourselfers can understand dishwashers and make repairs. Use this page in conjunction with my dishwasher repair guide to make dishwasher repairs easy. In its simplest form, dishwashers do nothing more than pump water up through a wash arm, causing it to spin. Thus, slinging water all over your dishes for a few minutes. Then pumping out the dirty water and starting all over again with clean water, this process is repeated several times through the cycle. During one of these times (normally about the third time), the soap will be released into the dishwasher. Below I will describe in more detail how dishwashers work.

Fill cycle

The dishwasher will fill the tub with water. The valve will power up and run water for a certain length of time. If for any reason the water level gets too high, the float switch will cut the valve off. Note that the float switch does not control the water level, its just there to prevent overflow. The water valve and the float switch can be purchased at

Pre Wash cycle

The dishwasher will go through a pre wash cycle. During pre wash, the pump will pump water through the wash arm causing it to spin, slinging water all over the dishes. Note that dishwashers will pre wash two to five times before entering the main wash.

Pump Out Cycle

The dishwasher will pump all the water out before each cycle. Some dishwashers use the same pump for pump out and for wash and some use separate pumps. Some dishwashers that use the same pump for pump out use a drain solenoid to redirect the water to the drain. Other dishwashers reverse the pump so that it pumps backward through the drain instead of through the wash arm. A few dishwashers are now using a separate pump for pump out. This is so the dishwasher can continue to washer until the pump out is almost finished to maximize efficiency. Drain pumps can be purchased at

Wash Cycle

After going through two to five pre wash cycles, the dishwasher will release the main wash soap and the rinse agent, and then enter into the main wash cycle. The washing action in the main wash will be the same as the pre wash, but the main wash cycle will be much longer. Some washers will also pump the water through a self-cleaning filter so that your dishes are cleaned with clean water.

Rinse Cycle

Once the wash cycle is over, the dishwasher will pump out the water and enter the rinse cycle. The rinse cycle will rinse all the soap off the dishes left behind from the main wash.

Heated Dry Cycle

After the dishwasher is done cleaning your dishes, it will enter the heated dry cycle. During the heated dry cycle a heating element will add heat to the tub of the dishwasher to dry the dishes. Old dishwashers used a fan in addition to the heat.

I hope this page helped you better understand how dishwashers work so that you can make repairs yourself, saving repair bills.

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