Water softening removes the high concentrations of dissolved “hard” minerals, primarily calcium and magnesium, that cause scale buildup in pipes and appliances. Removing these minerals prevents damage and improves the effectiveness of soaps and detergents. This process, however, alters the water’s chemical makeup, leading many to wonder about its suitability for daily consumption.
How Softening Affects Water Composition
Traditional water softeners operate using ion exchange to remove hardness minerals. Inside the softener tank, water passes through a bed of resin beads that are covered with positively charged sodium ions. As hard water flows through this resin, the calcium and magnesium ions—which carry a stronger positive charge—are attracted to the beads and are effectively swapped for the sodium ions. This exchange means that for every molecule of hardness removed, a proportional amount of sodium is released into the water. The final sodium concentration is directly tied to the initial hardness of the supply; water that is considered very hard will require a greater exchange of ions, resulting in a higher sodium content in the finished product.
The Impact of Sodium on General Health
For most healthy adults, the amount of sodium added during the softening process is considered negligible and poses no health concern. A water hardness level of 10 to 15 grains per gallon (GPG) is common, and this level of hardness typically adds about 28 to 35 milligrams of sodium to an 8-ounce glass of water. To put this in perspective, the average daily recommended limit for sodium intake is 2,300 milligrams. The sodium from a glass of softened water represents a very small fraction of this daily total. A single slice of white bread often contains around 114 to 211 milligrams of sodium, and an 8-ounce glass of milk contains about 120 milligrams. The general population can safely drink softened water without concern for excessive sodium intake.
When Softened Water Should Be Avoided
While safe for the majority, specific populations should avoid drinking softened water. Individuals on a medically prescribed, strictly low-sodium diet should avoid consuming softened water. Physicians often advise patients on these diets to limit total daily sodium intake, and any additional source, however small, may be a concern. The World Health Organization recommends a maximum sodium level of 200 milligrams per liter (mg/L) in drinking water for people with hypertension or other conditions requiring sodium restriction. A separate and important consideration is the preparation of infant formula. The kidneys of babies, especially those under six weeks old, are still developing and have a limited capacity to process excess minerals. Infant formulas are carefully balanced to contain the precise amount of nutrients, including sodium, necessary for a baby’s development. Using softened water, which can exceed the recommended limit of 200 mg/L of sodium for formula preparation, may disrupt this delicate mineral balance and is generally advised against by health authorities.
Options for Drinking Water in Softened Homes
For households that need the benefits of soft water for plumbing and appliances but require low-sodium drinking water, several practical alternatives are available. The simplest solution is to install a bypass line that directs unsoftened, or hard, water to one designated cold water tap, typically the kitchen sink. This allows the homeowner to use low-sodium water for drinking and cooking while the rest of the house receives softened water. Another highly effective option is installing a point-of-use reverse osmosis (RO) system, usually under the kitchen sink. Reverse osmosis works by forcing water through a semipermeable membrane that removes the vast majority of dissolved solids, including the sodium added during the softening process. This provides an ultra-purified water source that is safe for low-sodium diets and infant formula preparation. Households can also choose to use potassium chloride instead of sodium chloride salt to regenerate the softener, which replaces the hard minerals with potassium ions instead of sodium ions.