The Secret Life of Home Appliances: Dishwashers

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We explore what happens inside a dishwasher as it cleans.

In Stanley Kubrick’s sci-fi masterpiece, 2001: A Space Odyssey, the question is asked whether Hal—the infamous man-made robot that refuses to open the pod-bay doors — is truly self-aware and capable of free thought, or if he is merely an advanced network of transistors forever enslaved to the whim of his programmers?


The question is never quite answered, and it may take decades for scientists to come up with their own conclusions. But one thing is clear: Robots are everywhere. They’re all over your kitchen, your living room, your bathroom. We rely on them in more ways than we can imagine. How, exactly, do our robot-esque home appliances work? And if we can anthropomorphize for a moment, what goes on inside their heads?

I used to think that dishwashers were just hollow boxes that sprayed hot water all over the place. On a basic level, that's true, but that simplistic description belies the more complex and fascinating processes of modern dishwashers.

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Start-up and Heat-up

Each wash cycle starts with a human touch. Somebody pushes a button to select a wash cycle, sort of like the painting of the Creation of Adam on the ceiling of the Sistine Chapel (a totally fair comparison, right?).

Then the machine’s intake valve opens, and sprays water into the wash tub. The dishwasher’s heating unit (usually located beneath the lower rack) raises the temperature of the water to a predetermined temperature, which is controlled by an internal sensor.

Some machines are able to reach temps north of 160 degrees Fahrenheit, though sanitize cycles only need to reach 145 degrees to kill bacteria. The heating process usually takes about 10 minutes, depending on the dishwasher and wash cycle.

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Hot, Soapy, High-Pressure Spray

After the water heats up, detergent gets released into the tub. A motorized pump directs the hot, soapy water into the wash arms, which then creates a high-pressure jet-stream by forcing the frothy mixture through narrow channels. It's similar to what happens when you hold your thumb in front of a garden hose. The pressure also causes the wash arms to spin.

A forceful spray is a big part of getting the dishes clean, but anyone who has ever forgotten to load detergent into a dishwasher can attest to its importance—you might as well dump six gallons of water down the drain. Phosphates and enzymes in the detergent work to dissolve food stains, like a gang of microbial ninjas sent to assassinate filth with extreme prejudice. The hotter the water, the more effective the detergent. (We recorded this process, and edited the clip down to the most exciting bits.)

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This stage is the crux of the washing process, and it usually repeats itself over the course of an hour or so. The duration depends on a number of factors, though—cycle selection, wash options, soil levels, dishwasher type, and so on. The Asko D5434XLS, for example, takes more than two hours to complete a normal cycle, while the GE Profile PDWT280VSS finishes in a little over an hour. It should be obvious which machine is the better performer, though.

Drain and Dry

When the entire wash cycle completes, the water is drained from the base of the wash tub and pumped into your kitchen’s drainage pipes (or sink, if you’re using a portable machine). Most dishwashers then engage the drying component, which heats the air in the tub (via the heating element) and leaves your dishware nice and dry (and super hot!).

So your average dishwasher is not quite as intelligent as Hal, but it’s still a robot—controlled by a mechanized interface with predetermined cycle durations and stages. On some basic theoretical level, is that not what a robot is? It’s true we don’t really have to worry about that sinister spark of self-awareness and the ensuing robot apocalypse, but there’s clearly a lot more going on than we assume. Here’s to the singularity.