Commercial water dispensing machines may contain more contamination than tap water

Water dispensing machines in commercial spaces may contain higher levels of microbial contamination if they aren't cleaned regularly compared to the tap water sources supplying them that contain residual chlorine, according to a new study.

Loma Linda University researchers conducted a literature review of 70 published studies from around the world that examined commercial water nozzles and spigots. Their study, Microbiological quality of drinking water from water dispensers, was published in December 2025 by the AIMS Microbiology.

Researchers found that many studies identified bacterial growth in commercial water dispensers and restaurant soda fountains appearing within a few days after disinfection, far sooner than previously thought.

"Evidence suggests that internal system lines and dispensing outlets should be disinfected every two to four weeks, and every week in higher-use dispensers," the study stated.

"Filtering out residual chlorine that's in water makes an ideal situation for bacteria to grow. You've got to clean the tubes and change the filters regularly," said Ryan Sinclair, PhD, MPH, professor of environmental microbiology at Loma Linda University School of Public Health and supervising investigator of the study.

Sinclair has long studied water in underserved communities, particularly in the Inland Empire's desert regions of Indio and the Salton Sea. He and his team got the idea to study water in commercial spaces due to the trend of sporadic reports of contamination in water dispensers that had raised public health concerns, the study stated. Many residents in communities that are served contaminated tap water choose to purchase drinking water from commercial water vending machines or stores.

Commercial water vending machines "are intended to improve water quality through filtration, their performance depends heavily on maintenance, sanitation practices, filter replacement schedules, and biofilm control within the dispensing systems," the study stated. "When these are inadequate, [water vending machines] can introduce or enable the regrowth of microorganisms, leading to contamination levels that may equal or exceed those found in the original tap water source."

This research is the first known compilation of research from around the world on microbial contamination in water dispensing machines, Sinclair said.

"This review underscores the potential public health risks associated with water dispenser use, and highlights the need for increased vigilance, regular maintenance, and further research to ensure the safety of dispensed water," the study stated.