Water softeners: How much sodium do they add?

I'm on a low-sodium diet, so I'm looking for ways to reduce my sodium intake. How much sodium does a water softener add to our tap water?

- Bobby / Tennessee

Answer

The amount of sodium a water softener adds to tap water depends on the "hardness" of your water. The best way to decrease your sodium intake is by cutting back on table salt and processed foods. But the water from your tap also may add a significant amount of sodium to your diet. Reducing dietary sodium can lower systolic blood pressure by 2 to 8 millimeters of mercury (mm Hg).

Hard water contains large amounts of calcium and magnesium — dissolved from the soil by rainwater. A typical water-softening system removes calcium and magnesium ions from hard water and replaces them with sodium ions. The higher the concentration of calcium and magnesium, the more sodium needed to soften the water.

Your local health department can tell you the sodium and other mineral content of your community's water supply. (Water naturally contains some sodium before it's softened.)

This information can help you determine the total amount of sodium your tap water may have before being softened. It can also help you estimate the amount of sodium (milligrams per liter) a softener adds to your water. Here's how:

• Ask your local health department for the hardness of your water in grains per gallon.
• Multiply this number by 8 — or 7.866 to be more precise. This tells you how much sodium is added to your water by softening.
• Add this figure to the amount of naturally occurring sodium in your water — also from your local health department — to determine the total sodium.

One survey found that, as a general rule, an 8-ounce glass of softened tap water contains less than 12.5 milligrams of sodium. According to the Food and Drug Administration nutrient guidelines, this is in the very low-sodium range.

If you find that your tap water is high in sodium, you may consider:

• Switching to another type of water-purification system
• Buying demineralized water for drinking and cooking
• Softening only the hot water and using unsoftened cold water for drinking and cooking

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