Many people know of the issues with hard water and that soft water is better for the skin and hair, and is significantly more energy efficient; it extends the life of heaters, other appliances, and plumbing systems. However, nearly 90 percent of homes in the US have hard water.
Hard water presents a little-known problem: it increases the likelihood of contamination in the plumbing system including Legionella colonization. This is because hard water contains elevated levels of calcium and magnesium which, over time, cause scale formation; this makes the surface inside the pipes less smooth allowing bacteria to grow, according to research at the School of Sustainable Engineering at Arizona State University. Researchers also discovered that microbial biofilms (where Legionella typically colonize), do not form on smooth pipes, but can grow on scale that forms in pipes over time. The solution would be to use water softener to remove scaling, therefore reducing the possibility of biofilm formation.
This study at Arizona State University was the first of its kind to show the benefits of using water softener to prevent the development of biofilm in plumbing systems.