Hard water contains high concentrations of dissolved minerals, primarily calcium and magnesium ions. Water softeners remove these minerals, which cause scale buildup in pipes and appliances, by exchanging them for a different, less reactive ion. For the vast majority of healthy individuals, the resulting softened water is safe for consumption. However, specific health conditions or household situations introduce important caveats.
The Process of Water Softening
Water softeners operate using ion exchange to change the chemical composition of the water. As hard water enters the system, it flows over a bed of resin beads covered with positively charged sodium ions. These resin beads have a stronger attraction to the calcium and magnesium ions than they do to the sodium ions. The hardness minerals are stripped from the water and adhere to the resin beads, while the resin releases its sodium ions into the water, replacing the hardness minerals with sodium. The amount of sodium introduced is directly linked to the initial level of hardness removed, using the sodium component of the salt brine for this exchange reaction.
Sodium Content and Health Considerations
The sodium added during the ion exchange process is minimal for most people and does not make the water taste salty. For every grain of hardness removed per gallon of water, approximately 30 milligrams of sodium is introduced. This means a glass of moderately hard water (around 10 grains of hardness) will contain about 18 milligrams of added sodium. This small amount is negligible when compared to the average recommended daily intake of sodium for healthy adults, which is less than 2,300 milligrams. The vast majority of sodium in a person’s diet comes from packaged and processed foods, meaning the trace sodium from softened water does not pose a health concern for the general population.
Specific Scenarios and Medical Concerns
While most people can safely drink softened water, certain individuals must monitor their sodium intake more closely. People on severely sodium-restricted diets, often due to conditions like hypertension, kidney disease, or heart failure, should consult a physician about their water consumption. The added sodium, though small, may contribute to their overall dietary restrictions.
A second major concern is using softened water to prepare infant formula, particularly for newborns under six weeks old. Infant kidneys are still developing and cannot effectively process excess sodium. Pediatricians and health organizations advise against using softened water for formula if the sodium level is above 200 milligrams per liter.
A related scenario is when the source water is extremely hard, which can be 25 grains per gallon or more. In these cases, the ion exchange process adds a significantly higher amount of sodium, potentially pushing the level into a range that requires attention. An alternative softener solution involves using potassium chloride instead of sodium chloride, which exchanges potassium ions for hardness minerals.
Maintaining a Separate Drinking Water Source
For households with extreme water hardness or individuals with health concerns, maintaining a separate source of unsoftened drinking water is a practical solution. The most common method is to install a bypass line during the softener installation process. This line diverts the cold water supply to a specific tap, typically the kitchen sink or refrigerator, so that the water remains untreated by the softener.
Another, more comprehensive solution is to install a point-of-use reverse osmosis (RO) system on the drinking water tap. An RO system forces water through a semi-permeable membrane fine enough to block dissolved salts, including the sodium added by the water softener. RO systems are highly effective, typically removing 95% to 99% of the sodium, providing highly purified water that meets the needs of those on restricted diets or for preparing infant formula. This method ensures all household water is softened for plumbing protection, while providing a dedicated source of low-sodium drinking water.