Dishwasher vs hand washing water use comes up every time I write about how to use and maintain a dishwasher: Which is more cost-effective: Handwashing dishes or using the dishwasher?
For many readers, handwashing dishes just feels better and is something hard to let go of, especially for those who don’t use enough dishes to fill the dishwasher more than a couple of times a week.
But is low-tech handwashing just as effective as a high-tech dishwasher? Dishwasher vs hand washing water use? All things considered, the answer might surprise you.
Health and Safety
To kill the germs and bacteria on dirty dishes, water must reach a scalding 140° F, according to Kelly Reynolds, Ph.D., an associate professor of environmental health sciences at the University of Arizona. But here’s the problem: If you set your home water heater to that temperature, you’ll put family members at risk of scalding when using hot water in tubs, showers, and sinks.
Most home water heaters are set to 120°F to avoid scalding, so getting the water hot enough from the tap for hand washing dishes is impossible. And even if you could, 140° F is much hotter than your hands could stand for the minimum required 2-minutes those dishes would need to be exposed to that high temperature.
Since the early 1990s, most dishwashers in the U.S. have built-in heaters to boost water temperature to 140–145° F, the temperature recommended by manufacturers for optimum dishwashing performance, and by food safety experts for killing bacteria.
The advantage of a dishwasher with a booster heater is that you are assured 140–145°F in the dishwasher, but at the same time you can turn down your water heater thermostat to 120°F, which will significantly reduce your household water heating costs.
Not everyone has an automatic dishwasher. Or should you worry about Grandma’s Wedgwood, which is too delicate for the dishwasher—or your grandma who doesn’t own a dishwasher? No worries! Hand-washing can do an acceptable job of cleaning, but if you want your dishes sanitized, according to the Oregon State University Extension Service, you should add one step to the process:
After scrubbing with soap and water, soak everything for 5 to 10 minutes in 1 gallon of hot water and 1 tablespoon of chlorine bleach (this ratio works for a sinkful of dishes). Don’t re-rinse. Instead, pull the dishes out of the sanitizing rinse water and them to air dry in a rack or on a drying mat.
The bleach will kill any microorganisms that hand-washing alone cannot eradicate—an especially good idea if anyone in the house is sick. As everything dries, the bleach will evaporate, leaving your dishes clean and sanitized.
Hand washing dishes typically uses a lot more water than a dishwasher. Unless you could get that sink full of dirty dishes hand washed with soap and rinsed with the water running from the tap in fewer than 2 minutes, you’re likely using a lot more water than a current automatic dishwasher model requires. And in most cases, a lot more if you pre-rinse, wash, and then rinse again.
That’s because, according to the U.S. Energy Department, a federal standard kicked in for dishwashers requiring a 20-percent reduction in the amount of water it uses. If yours is a highly efficient Energy Star-certified dishwasher, it uses less than 4.25 gallons of water per cycle.
Not long ago, we remodeled our kitchen. I was without a dishwasher for what seemed like forever, but in reality, it was about a month. That doesn’t mean I stopped cooking or we stopped eating a home. I just had to find other ways to do the job.
Health, safety, and economics aside, it took too much time to get the same job done with a fully operational dishwasher. To keep up, it seemed like I was hand washing all the time. The drying rack was forever full. Even so, I had dirty dishes in the make-shift sink and clean dishes always waiting for me to move from the drying rack to the cupboard.
Not only does my dishwasher save energy and water, it makes my life much easier.
The evidence is clear regarding dishwasher vs hand washing water use. A dishwasher is far more efficient than hand-washing dishes. It’s safer, faster, and cheaper than even the most frugal hand washing method.