Water Hardness
Dissolved metal ions, measured as calcium carbonate
Hardness refers to dissolved metal ions in water, typically calcium and magnesium, along with contributing ions such as aluminum, barium, iron, manganese, and zinc, and is typically expressed as milligrams of calcium carbonate equivalent per liter.
Soft to very hard
Water hardness is commonly classified, based on equivalent calcium carbonate, as follows:
Hardness is most commonly measured by titration with an EDTA (ethylenediaminetetraacetate) solution, which reacts with magnesium and calcium ions.
Soap scum and spotted dishes
The main residential concern with hard water is the potential for precipitates to form, particularly when heated — an effect sometimes called “temporary hardness.” Historically, hardness was described by water’s capacity to react with soap: hard water requires more soap to lather, because the sodium/potassium soap converts to an insoluble non-detergent, producing soap scum and the spotting sometimes seen on dishes after a dishwasher cycle.
Both calcium and magnesium are essential minerals with health benefits, and while food remains the primary dietary source, water can be a meaningful contributor for some populations. Dissolved minerals also affect the taste of drinking water, with acceptability varying by individual familiarity and preference.
Soft water is not automatically safer
Corrosion and scaling are functions of hardness, pH, and alkalinity. Hard water forms scale deposits — mainly calcium carbonate, magnesium hydroxide, and calcium sulfate — that clog plumbing, boilers, and heat exchangers. Excessively hard water can carry its own corrosion tendencies, but unstabilized soft water tends to be more corrosive still, introducing metals such as copper, lead, zinc, and cadmium into drinking water.
Naturally soft, or softened
There’s an important distinction between naturally soft water and water softened through cation exchange, where calcium and magnesium are displaced by sodium. Naturally soft water is more corrosive and typically requires stabilization — usually through increased alkalinity and/or corrosion-inhibiting additives such as phosphates. Rainwater is typically soft, and it would be unusual for groundwater to present softness issues. Hardness isn’t directly regulated by the EPA, though it can be indirectly addressed through the Secondary Drinking Water Standards for total dissolved solids.
Usually unnecessary for public systems
Because hard water isn’t a health hazard — and can even be considered a dietary source of calcium and magnesium — and most detergents already counteract its effects, water hardness treatment and softening are generally unnecessary for public systems, though softening may be recommended for water feeding a hot water system.
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Whether you want a new water treatment system installed, need your current one inspected and repaired, or just want a free quote, contact the WETS LLC. With years of experience in the industry, our skilled team members are trained and knowledgeable with a variety of leading water equipment and products. Our certified water purification experts are here to help.
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