How Dishwashers Work

By Dave Donovan

Family get-togethers. We all love them, even if we have to sit through Uncle Carl's re-enactment of the time he caught the two-headed turtle yet again. But the one thing that nobody likes is having to clean up all the dirty dishes afterward. Piles of plates, scads of silverware, and groups of glasses, and nobody's jumping up to volunteer, especially Uncle Carl!

You may not know it, but we all have a spoiled, rich woman to thank for our modern day dishwasher. Her name was Josephine Cochrane, the granddaughter of John Fitch, the man who invented the steamboat. Josephine was a spoiled woman whose hands never touched a dirty plate. She got fed up with her servants chipping her fragile china and eventually invented the hand-powered dishwasher that premiered at the 1893 Chicago's World Fair. Over the years, advancements in plumbing and the inclusion of heating elements lead to the dishwashers we find in most homes today.

But what about that caked-on grime? How can water and a little detergent get the dishes so clean, you ask? Come along with me as we learn more about your dishwasher.

Dishwashers need both water and electricity to function. Most dishwashers are wired underneath and to the rear of the unit. Only the hot water line gets hooked up to a dishwasher - when dealing with dirty dishes, cold or warm water just won't cut it. The drainage hose gets connected to your garbage disposal, if you have one. If you've ever seen a dishwasher uninstalled, you may have noticed a quilt-type blanket covering the top and sides. That blanket is a sound absorber. It dampens the noise level so you can still carry on a conversation while the machine is running. The price of your machine may actually depend on the type of sound absorber it has. Of course, noisier ones are less expensive and quiet ones more expensive. But as you'll see, other than the sound absorber, most dishwashers are very similar.

Dishwashers, despite the price tags, generally have three things in common. They all have motors and pumps. They all have a control panel. And they all have similar interior racks. Most dish racks have generalized locations for glasses, silverware, and plates. Some racks are adjustable to fit larger items. The racks are usually on little plastic wheels so you can roll them out for easier loading and unloading. The racks are coated with a heat protected plastic coating to help prevent dishes from cracking.

If you open the door, you'll see two reservoirs on the door itself. One usually has a lid and one is open. The detergent goes in both. After the wash reaches a certain point, it opens the lid on the second reservoir and more detergent is made available. You may notice that sometimes the lid won't lock on the reservoir. That's because the control timer didn't reach a set point the last time the dishwasher was used. Someone may have stopped the cycle early. You will need to manually turn the dial until you hear the reservoir cap click. There may also be a smaller reservoir for an additive to help the rinse cycle.

The control panel dictates everything that happens within a cycle. However, even the control panel won't work if the door lock isn't engaged. The door lock is a handle type of kill-switch that needs to be locked in order for the machine to work. It's similar to the type of door lock on self-cleaning ovens. If the washer is in use and you unlock the door, the machine automatically turns off. Most control panels have a number of washing options available. There are settings for economy washing, high-heat drying, quick rinse, heavy duty wash, pots and pans, and so on.

The control panel's primary fixture point is the dial. The dial is where most settings are made, and it works very similar to a timer. You turn the dial to how long you want the dishwasher to run, engage the door lock and presto! Like on a clothes washer, there is a motor that turns the dial and at certain points, closes or opens contacts that signal certain events such as rinse or drain. In most cases, there are pushbuttons that allow you to choose between heat or no-heat drying, economy wash, and so on. These pushbuttons also engage contacts that send electric current to whatever is being selected.

Most American-made dishwashers have one motor that is responsible for bringing the water in, and draining it out of the machine. The motor pulls the water in and forces it out of the washer arms at a high rate of speed. The temperature of the water and the speed at which it hits the dishes cause even the toughest grime to loosen up. After the wash cycle is finished, the motor pulls the water back down the drain and pumps it out of the machine. Some dishwashers have a heating element that continues to heat the water as it's being pumped into the machine.

Now that the hot water and detergent blasted all that barbeque sauce off the plates, it's time for them to dry. Most modern dishwashers come with a heating element noticeable in the bottom of the wash basin. It's a black metal tube that usually follows the contour of the basin. If you selected to heat-dry the dishes, then after the rinse cycle, the element flares up and speeds up the drying time. Many people use this option as a plate warmer for parties, bypassing the wash cycle and just using the heat-dry cycle. To help speed drying time even more, many dishwashers have small fans that bring air in to circulate and help the cause.

One common misconception is the belief that washing the dishes in the dishwasher sterilizes them. That's not the case. The water in the home dishwasher reaches 130 to 150 degrees; it would need to reach 250 degrees to sterilize. Even commercial dishwashers can only reach 180 degrees, allowing sanitizing, but not sterilizing.

Now that we've gone over how the dishwasher works, you may be experiencing some problems with your machine that you need to address. Luckily for you, we have a repair guide to help you fix the most common problems you may face. OK, the dishwasher's finished, anyone want to volunteer to empty it? Uncle Carl? Anyone?