Freestanding water vending machines, often marketed as cleaner alternatives to tap water, may not always deliver what consumers expect.
A new study published in Environmental Science & Technology found that water from some U.S. drinking water kiosks contained elevated lead levels, in some cases nearly twice the concentration recommended by the U.S. Environmental Protection Agency.
Researchers sampled water from 20 kiosks across Iowa and nearby states, including Illinois, Kansas, Missouri, Arkansas and Oklahoma. They compared kiosk water to municipal tap water collected within a mile of each machine. Most kiosks advertised treatment using reverse osmosis, a filtration method designed to remove contaminants such as per- and polyfluoroalkyl substances, also known as PFAS.
The analysis found no microbial contamination in any of the samples. Reverse osmosis treatment effectively reduced most PFAS levels compared to local tap water. However, some kiosk samples showed higher lead concentrations than the municipal water they originated from.
“Currently, water kiosks are not regulated the same as tap water; their water is not tested for lead or other metals,” said Samantha Zuhlke, a corresponding author of the study.
The researchers traced the lead to corrosion of internal brass plumbing components inside the kiosks. Although marketed as “lead-free,” these components can still contain small amounts of lead. Reverse osmosis treatment lowers water pH and alkalinity, which can make water more corrosive and increase the likelihood that metals leach from plumbing materials.
“This work adds to growing evidence that allowable levels of lead in ‘lead-free’ plumbing can still be problematic sources of lead in drinking water when such plumbing is exposed to certain types of water, like that generated after RO treatment,” said co-author David Cwiertny.
The study included a limited number of kiosks and was concentrated in the Midwest, so the findings are not necessarily representative of all vending machines nationwide. Still, the results highlight tradeoffs that can occur with water treatment systems. Reverse osmosis can reduce certain chemical contaminants, but changes in water chemistry may introduce other risks if plumbing materials are not compatible.
For consumers, the findings underscore that water quality depends not only on source water but also on how it is treated and stored. Municipal tap water in the United States is subject to federal testing requirements, including monitoring for lead. Kiosk water is regulated differently, and testing requirements may vary.
Lead exposure is associated with neurological and cardiovascular risks, particularly with long-term exposure. While the study does not suggest that all kiosk water is unsafe, it suggests that maintenance practices and plumbing materials matter.
Consumers who rely on water kiosks may want to ask operators about maintenance schedules, filter replacement and plumbing materials. Those using reverse osmosis systems at home may also consider whether their systems include remineralization or corrosion control steps designed to stabilize water chemistry.
The research was supported by the University of Iowa’s Center for Social Science Innovation and the Office of Undergraduate Research, and conducted through the University of Iowa Center for Health Effects of Environmental Contamination, which receives support from the Iowa Department of Natural Resources.