Hot Water for Handwashing: Not So Great After All

Photo: Kathea Pinto/FlickrIf you're like me, you probably learned from a young age that when you wash your hands, you need to turn the tap to hot, lather up, and rinse your hands. Ideally, you should be running your hands under water for at least 20 seconds (singing the alphabet song to yourself helps with timing this, FYI), to allow the surfactant action of the soap to help the water fully lift any dirt, grime, and bacteria. Then you can dry off and pat yourself on the back: you did your part to prevent the spread of germs!

Only...about that hot water. It's estimated that around 800 billion hand washes occur in the United States, from sinks outside patient rooms in hospitals to your very own bathroom. The combined energy needed to heat the water for all those handwashings is equivalent to the emissions of Barbados. WHOA!

But you need that hot water, right? Because hot water kills germs!

Wrong. Well, sort of wrong. In order to effectively kill most germs, hot water needs to be close to boiling -- which is why medical instruments are boiled to sterilize them, and why dishwashers and other automated cleaning equipment gets to boiling or higher for washing. I don't know if you've tried washing your hands with boiling water lately, but it's not a pleasant or even feasible experience. After the recommended 20 seconds, your scalded hands would be throbbing with blisters.

So washing with hot water only works when the water is too hot to tolerate. Washing with warm water, on the other hand, can actually soften the upper layers of the skin, making you more vulnerable to germs. Washing with cool or cold water? May be just what the doctor (and the planet) ordered. The key components of hand washing are the soap, friction (to lift debris from your skin), and a steady flow of water.

By switching to cold or cool water for handwashing, you can save a substantial amount of energy, although it's not always immensely comfortable at cold times of the year, which is why you need a nice fluffy towel or an eco-friendly air-dryer to absorb all that water when you're done. And if you're having problems with persistent cold in your house, it's time to call a Minneapolis heating company for an energy audit and a discussion about your options for better controlling the interior temperature.

Your individual handwashing decisions might not seem like a big deal, but changing the way people wash their hands as a whole could generate huge energy savings across the country, which is great news for the planet ... and your pocketbook.

The study was conducted by Amanda R. Carrico, who looks at a variety of ways to address and reduce energy use in the household. Since water heating is a major energy hog, she was particularly interested in changing the way people use and think about water in their homes. This study serves as yet another reminder that it's okay to turn down your water heater to reduce energy expenditure and energy costs. When you heat your water to a temperature you never actually use, you're wasting energy. Try dropping your water heater to 120 degrees, if you haven't already, and see if that makes a difference in energy usage.

If you really want to reduce energy use when it comes to your water heating practices, talk to a savvy plumber about recirculating pumps and on-demand heaters, which provide even more savings by reducing loss and only heating water when you need it. It's also advisable to insulate pipes to minimize heat loss, thereby reducing the demand on your water heater even more.

Seemingly small actions can make a big difference when they spread across entire communities. So why not change up your handwashing routine?

Katie Marks writes for

Updated April 11, 2018.

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