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last_updated_date Last updated: January 31, 2020

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Mechanisms 101: How Does A Dishwasher Work?

PUBLISHED: January 31, 2020 4 MINS READ

how does a dishwasher work

Dishwashers are such an indispensable part of American homes that it sounds strange that they became available for sale to the general public only around the late 1950s. This appliance cuts down drastically on the manual labor involved in washing dishes. You also save water as they use less water than washing dishes by hand does. To be able to properly maintain your dishwasher, it is useful to know how does a dishwasher work.

The Original Dishwasher

Since their invention by Josephine Cochrane, dishwashers are one of the few appliances to have not changed too much from their original design. Ms. Cochrane, one of the early female inventors, was assisted by George Butters, a mechanic. Her design was not electrical; working the device involved pumping the water by hand. 

The dishwasher setup consisted of a washing apparatus inside a copper boiler. Cochrane measured out the dishes to be washed and constructed wire racks as compartments to hold the dishware. The compartments were placed on a wheel that lay flat at the bottom of the copper boiler. An external water pumping mechanism with 2 pumps was connected to a motor turning the wheel. 

Each pump was operated by a rod. Heaving this rod up and down would cause a jet of soapy water to spray the dishes from every possible direction. A second jet rinsed away the soiled soapy water using clean water. 

Josephine Cochrane’s dishwashing company, Cochran’s Crescent Washing Machine Company is the precursor of the famous KitchenAid brand. 

Old dishwashers

The Modern Dishwasher

Of course, dishwashers today run on electricity. There are two kinds based on the way of installation: a built-in dishwasher and a portable dishwasher.

The main washing chamber is water-tight and contains racks at different heights and of sizes to fit pots, pans, dishes, spoons, etc. There is a shallow basin at the bottom that fills up with water and has heating elements, a food filter, and a float valve. 

The center of the basin has a fill valve and spray arm. The top of the washing chamber has another spray arm. The spray arms double as rotating paddles. There are pipes along the walls to take water up to the upper spray arm.

A dishwasher has a soap dispenser where one can add liquid or solid detergent. When the machine runs, the soap is dropped into the water basin from where it is drawn up.

How Does A Dishwasher Work: What Happens Inside? 

  1. First, you load the dishware, add the soap and then pick the right wash cycle.
  2. Thereupon, the central basin at the bottom starts filling with water.
  3. If the dishwasher is the kind that takes in heated water directly, the heating elements won’t be present; else the water is heated at the bottom to about 130°-140° F.
  4. The float valve ensures that the basin does not overflow. This, as well as the heating element, can be replaced by a home warranty service provider if you have purchased dishwasher coverage.
  5. The pump at the bottom sends the heated water up through the pipes to both the spray arms/rotating paddles. 
  6. The water moves through the arms at high pressure causing them to rotate. The rotating spray arms disperse the water throughout the chamber and reach all the dishware if loaded correctly.
  7. The water falls back into the basin and is sent back into the arms by the same process. The food particles are trapped by the food filter.
  8. As the upper part of the dishwasher is cooler, the instructions usually ask you to place heat-sensitive dishware there.
  9. When the wash cycle is over the dirty water is drained away and the process repeats in the rinse cycle with clean water. If you see your dishwasher not draining, call your home warranty helpline.
  10. You can dry the dishware by selecting the drying cycle, which will use the heating element to heat up all the remaining moisture into steam. This moves out of the machine. Not using this step is more energy efficient.

Now you know how your dishwasher works!

The only learning curve in using a dishwasher is figuring out the optimum way to load it. Some people advocate the use of rinse aid, a substance that makes the water spread out in thin sheets rather than bead up, leaving your cutlery cleaner and drier once it is out. With good maintenance, your dishwasher can serve you well for years. Consider protecting it with a home warranty once the manufacturer guarantee expires.

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