Softened water is water treated to remove high concentrations of hardness minerals like calcium and magnesium, which cause scale buildup and affect soap performance. People often wonder about the safety of drinking this water, especially when boiled. The primary concern relates to what the softening process adds to the water and how boiling changes that composition.
Understanding Water Softening
Water softeners operate using a principle called ion exchange to remove the minerals that make water “hard.” Hardness minerals, primarily calcium and magnesium ions, are positively charged. The softening unit contains a resin bed made of small beads coated with positively charged sodium ions.
As hard water passes through this resin bed, the calcium and magnesium ions are attracted to the resin beads and displace the sodium ions. For every ion of calcium or magnesium removed, a small amount of sodium is released into the water supply. The level of sodium added is directly proportional to the original hardness of the water supply. This process ensures the water that exits the softener is “soft,” but it also means the water now contains a slightly elevated level of sodium compared to the original source.
What Happens When Softened Water Is Boiled
Boiling water is an effective method for killing bacteria and other microbial pathogens. However, boiling does not remove dissolved solid minerals or salts, including the sodium ions introduced during the softening process.
In fact, boiling water causes the water itself to turn into steam and evaporate, which reduces the overall volume of the liquid remaining. This evaporation leaves the dissolved solids, like sodium, behind in a smaller amount of water. Consequently, boiling actually increases the concentration of sodium in the remaining softened water. For example, if a cup of softened water contains a certain amount of sodium, boiling away half the water will result in the remaining liquid containing nearly double the original sodium concentration. Boiling softened water does not purify it of its sodium content; it only intensifies it.
Guidelines for Safe Consumption
For most healthy adults, drinking boiled softened water is generally safe and poses no health risk, as the added sodium is minimal compared to the typical daily intake from food. The amount of sodium added to softened water is often less than what is found in a slice of bread or a glass of milk. The primary concern only arises when the original water source is exceptionally hard, which leads to a significantly higher sodium exchange.
Infants and Formula Preparation
Caution is strongly advised when preparing infant formula with boiled softened water. The developing kidneys of infants, especially those under six weeks old, cannot process excess sodium effectively. Health regulations often recommend that water used for formula should contain no more than 200 milligrams of sodium per liter to ensure the total sodium level remains safe for the baby.
Sodium-Restricted Diets
Individuals on a medically advised, sodium-restricted diet, such as those managing hypertension or kidney issues, should also exercise caution. Even small increases in daily sodium intake can be problematic for this group, and the concentration effect from boiling must be considered. While the amount of sodium is often small, these individuals should consult their doctor regarding their specific dietary limits.
Practical Solution
A common and practical solution is to install a dedicated tap that bypasses the water softener entirely, often at the kitchen sink. This ensures a supply of unsoftened, or “hard,” water for drinking and cooking purposes, which can then be boiled without the concern of elevated sodium levels. This simple bypass allows the household to enjoy the benefits of soft water for bathing and appliances while ensuring safe water is available for consumption.