Just three years ago, a study conducted by the University of Westminster, London, determined that the "hygenic" warm air hand dryers commonly found in public washrooms actually left users with more bacteria on their hands than if they'd simply used paper towels. Now, it seems that the good name of hands-free electronic-eye faucets is being similarly besmirched – researchers at The Johns Hopkins Hospital in Baltimore have discovered that water coming from such faucets contains more Legionella bacteria than that dispensed by conventional fixtures. Their theory is that the high-tech faucets' complex inner workings are to blame.

The hands-free faucets use a sensor to detect when a user's hands are present, at which point the water will automatically come on for a preset amount of time. Given that the whole process involves no touching of anything, it would indeed appear to be more hygienic than a system in which multiple users touch hot and cold water handles with their unwashed hands. The folks at Johns Hopkins and other U.S. hospitals obviously thought so, and proceeded to introduce the faucets in patient care and public areas over a decade ago.

When Johns Hopkins staff were testing how often their water system needed to be flushed, however, they were surprised to discover Legionella growing in 50 percent of the cultured water samples from 20 hands-free faucets, as compared to only 15 percent in samples from 20 manual faucets in the same areas. While Legionella pose little risk to healthy individuals, they can cause serious infections in people with weakened immune systems.

The water from the traditional faucets was also found to contain just half the amount of other types of bacteria.

Although the reasons for the difference are unclear, the researchers suspect that the complex valve components of the newer faucets offer more surface area and hiding places for bacteria, which remain present even after standard hospital water disinfection methods. Conventional faucets, on the other hand, have few internal parts.

Johns Hopkins has since replaced all 20 of its newest hands-free faucets with manual models, and is in the process of replacing 100 similar faucets throughout the hospital. The research team now plans on working with manufacturers of hands-free faucets, to devise new ways of building them so that they can be more easily and thoroughly cleaned.