The phrase refers to the processes and techniques employed to reduce the concentration of dissolved minerals, primarily calcium and magnesium, in water. High concentrations of these minerals characterize hard water. For example, water leaving unsightly scale buildup on plumbing fixtures or hindering the effectiveness of soaps is likely hard water.
Addressing water hardness is crucial due to its impacts on household appliances, plumbing infrastructure, and even personal hygiene. Mineral buildup can shorten the lifespan of water heaters and dishwashers, increase energy consumption, and reduce the efficiency of soaps and detergents. Historically, methods to mitigate hardness have ranged from simple boiling to more sophisticated chemical treatments.