With an small electronic sensor inside, automatic faucets can start and stop the flow of water when people wash their hands. These faucets save a lot of water, which is one reason they are found in busy public bathrooms. Another reason is because of concerns about the spread of infection by people touching the handles on traditional faucets.
Hospitals started using automatic faucets about ten years ago. But a new study at one hospital finds that these devices may not always be worth the savings in water use.