However, this weak carbonic acid solution increases the system's capacity to dissolve minerals as it flows through the watershed , which in turn increases the alkalinity of the water. This cyclic movement keeps the environment in balance. Hardness Traditionally, hardness was defined as the ability of water to precipitate soap. Hardness has not been of particular interest to limnologists in the past, but was of significant importance to aquatic chemists and engineers working with water quality in water treatment plants. Hardness can be readily observed as a residual precipitate left on containers following evaporation of hard water.
Hard water is of concern to the homeowner as deposits form on plumbing fixtures and appliances.
Home water treatment systems are often installed to treat hard water. Hard water is not harmful to humans, and contains many of the minerals needed for normal plant and animal growth, but may affect the tolerance of fishes to toxic metals. Mine drainage waste may contribute large amounts of sulfates through pyrite oxidation. In potable water, the salty taste produced by chloride concentrations is variable and dependent on the chemical composition of water. Cl - may have a detectable salty taste if the cation is sodium.