Softened water is generally considered safe for consumption for most people, but the process introduces a small amount of sodium, which can be a concern for individuals with specific health needs. A water softener’s primary function is to remove the minerals that cause water hardness, mainly calcium and magnesium, which are responsible for scale buildup in pipes and appliances. The overall health impact depends heavily on the initial hardness of the source water and the individual’s dietary restrictions. The small increase in sodium is often negligible compared to the daily intake from food.
The Process of Ion Exchange
The mechanism behind a standard water softener is called ion exchange, a chemical swap that neutralizes the “hard” minerals. Hard water flows through a tank containing resin beads coated with positively charged sodium ions. These resin beads have a stronger attraction to the calcium and magnesium ions.
As the hard water passes over the beads, the calcium and magnesium ions attach to the resin, displacing the sodium ions. The released sodium ions are carried away with the water, resulting in soft water that flows through the household plumbing. The resin beads eventually become saturated with the hardness minerals, requiring the system to enter a regeneration cycle. During regeneration, a concentrated salt brine solution flushes the resin, forcing the calcium and magnesium off the beads and replacing them with a fresh supply of sodium ions.
Sodium Content and Health Implications
The amount of sodium added to the water is directly proportional to the original water hardness. For every grain of hardness removed, approximately 7.5 to 8 milligrams of sodium are added to each liter of water. Therefore, very hard water will have a higher sodium content after softening than moderately hard water. For example, water with 10 grains per gallon (GPG) of hardness will have about 80 mg of sodium per liter after softening, roughly equivalent to 12 mg per 8-ounce glass.
Most healthy individuals consume far more sodium through their regular diet than from drinking softened water. The typical daily recommended intake is 2,300 mg, making the contribution from softened water relatively small. However, the added sodium can become a factor for specific populations, particularly those on severely restricted-sodium diets. People with conditions such as hypertension, kidney disease, or heart conditions are often advised to limit their sodium intake.
For a person on a strict low-sodium diet, softened water could potentially contribute up to 10% of their daily sodium allowance. Infants are another group to consider, and many pediatricians advise using unsoftened or specially filtered water for mixing formula. If the source water is exceptionally hard, the resulting sodium concentration may exceed the concern level for those with medical restrictions. Consulting with a physician or dietitian is the best way to determine if the sodium level in your softened water is a health concern.
Variables That Affect Water Safety
The initial hardness of the water is the primary variable, as it dictates the amount of sodium exchanged into the water. Harder water requires more sodium to complete the ion exchange, resulting in a higher final sodium concentration. In addition to sodium chloride, some users opt for potassium chloride, which replaces hardness minerals with potassium instead of sodium. Using potassium chloride eliminates the concern of added sodium, though this alternative is typically more expensive and may require up to 30% more product to achieve the same softening level.
System maintenance is another factor that impacts the water’s safety and quality. A poorly maintained water softener can develop problems like a salt bridge, where the salt hardens and prevents proper regeneration. This can result in hard water flowing through the system, or a dirty brine tank could harbor bacteria if left uncleaned. A common, non-safety-related effect is a slight change in taste, which some people describe as faintly metallic or slick.
Alternatives for Drinking Water
For those concerned about the added sodium or the taste of softened water, several practical alternatives allow for soft water benefits without consuming the sodium. One common solution is to install a bypass line that directs the main water supply to the kitchen cold water tap before it reaches the water softener. This modification ensures that unsoftened, hard water is available specifically for drinking and cooking.
Another effective option is to install a point-of-use filtration system, such as a Reverse Osmosis (RO) system, on a dedicated drinking water faucet. An RO system works by forcing water through a semi-permeable membrane fine enough to remove the added sodium ions, along with other dissolved solids and contaminants. Using an RO system on softened water is beneficial because the soft water prevents the hardness minerals from clogging the delicate membrane, improving the filter’s efficiency and lifespan.