I asked the inventor about his design and when consumers might see the tech in their homes.

One challenge of current water heater designs is staying hot enough to kill harmful bacteria like Legionella pneumophila, which can cause Legionnaires’ disease. A new water heater design, developed and patented by researchers at the National Institute of Standards and Technology, aims to raise tank temperatures to 160 degrees Fahrenheit, which spells instant doom for Legionella bacteria.

Legionella bacteria love warm water, so while they struggle to survive in a water heater tank set to 120 F, they’re more than comfortable elsewhere in a home’s hot water pipes. It’s technically possible to achieve sufficient temperatures with existing water heaters, but those temperatures are also likely to scald human skin whenever you turn on the faucet.

The biggest innovation of this new design is how it finds a new use for heat exchangers, the same technology behind air conditioners, heat pumps, furnaces and refrigerators. I wanted to know more, so I reached out to David Yashar, a NIST mechanical engineer behind the new design.

As Yashar and his team researched ways to kill Legionella bacteria, they needed to figure out how to make tank temperatures around 160 F safe and practical for humans. They ultimately landed on the concept of using cold water entering the water heater to cool the hot water leaving the tank with an unmixed heat exchanger that contains the water inlet and outlet.

The principle behind unmixed heat exchangers—where the fluids don’t mix—is that incoming cold water gets a heating boost from the hot-water outlet while cooling the water to safe levels for people.

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