Everything You Didn’t Know You Wanted to Know About Dishwashers

Growing up American-born-Chinese, my parents never ran the dishwasher. A “dishwasher” was not an appliance used to clean dishes, but rather a premium two-tiered drying rack system with a pull-down door, or “a waste of water and electricity”. My sister and I learned about the myth of this American machine in the books we read, the movies we watched, and the shows we saw on television, but we never got to use it for ourselves.

Not until recently, having moved out from home, did I run a dishwasher for the first time. Naturally, I had many questions surrounding this mythical appliance. How effective is it at cleaning dishes? Does it actually save water? How does it work?

Fear not, for I have done the research and can answer all these questions.

How it works

Dishwashers are like a black box: although it’s simple to operate, its mechanisms are unclear. What exactly happens when you close the door and press “start”?

  1. Initial Rinse Cycle: The first thing the dishwasher does is fill up with 2–3 gallons of water. The heating element turns on and makes the water hot, anywhere from 120–160 degrees Fahrenheit. The water collects at the bottom of the dishwasher and is transported through tubes to propellers placed under the dishes. These propellers rotate and spray jets of water upwards, chipping away at the food bits and grime with each pass. The water is recycled like a fountain, with a filter preventing the more solid pieces of food from being jettisoned upwards.
  2. Wash Cycle: At some point, the soap box automatically opens and detergent falls into the pool of recycled water below. This helps cut away at the grease leftover on the plates.
  3. Draining Cycle: The soapy water is drained through the same pipe connected to your sink, which is why dishwashers are typically placed right next to the sink. The water must be drained to prepare for the final rinse cycle.
  4. Final Rinse Cycle: The dishwasher fills with another 2–3 gallons of clean water, and water is shot upwards in the same fashion in order to clean the dishes. You can add rinse aid to the dishwasher in order to soften the water for this process.
  5. Drying Cycle: There are multiple ways how dishwashers dry dishes, but they all revolve around heat. If you pay attention to the dishwasher door, most dishwashers feature a vent that allow the hot air to escape. If you want to read more about how drying works, this article will explain everything.

Economics

I always thought that dishwashers continually used new, clean water to hose down dishes, and found it difficult to believe that it would be more efficient than hand washing. As it turns out, the reason dishwashers are so efficient is precisely because they don’t use water in the same way as in hand washing. Instead of using new water, dishwashers opt to recycle the water for each cycle. Dishwashers typically only use 4–6 gallons of water in total.

Okay, but how does that stack up against hand washing? As it turns out, the typical kitchen faucet runs at a flow rate of 2 gallons per minute. Following this line of logic, any amount of dishes that would normally take more than 3 minutes to hand wash should be washed by a dishwasher. 3 minutes is not a long time; according to this study conducted at the University of Bonn in Germany, “the dishwasher uses only half the energy, one-sixth of the water, and less soap.”

In conclusion, you should most definitely run the dishwasher whenever you have enough dishes to fill up the dishwasher. The golden number is 3 minutes — if you believe you can wash the dishes at hand in less than 3 minutes, then go for it.

Things I did not know

  • As seen from this enthralling 4k GoPro video, the jets are angled ever so slightly outwards from the center of the dishwasher. You should place dishes so that the dirty side faces the inside of the dishwasher — not all lined up in one direction. The outside dishes will be washed less thoroughly than the inside dishes.
  • Don’t put plastic on the bottom rack. The heating element gets really hot, and you don’t want to melt the plastic.
  • Don’t load wood into the dishwasher. Since the water gets so hot, you can easily warp the wet wood during the washing/drying cycle.
  • The dishwasher is a mini-fountain, go figure.

Sources

Hi! I’m Arthur, a software engineer by day and a hobbyist by night.

https://arthurpan.me/

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