Sodium Content of Your Drinking Water

The Dietary Guidelines for Americans published by the U.S. Department of Agriculture and Health and Human Services recommend that Americans reduce their intake of sodium. A safe and adequate level of sodium for Americans is 1100-3300 milligrams (mg) per day, about half the amount Americans currently consume.

Too much sodium has been identified as a risk factor for high blood pressure, which affects one in four Americans. Although some people can consume high levels of sodium without increased blood pressure, others cannot. Other risk factors for high blood pressure include a family history of the disease and overweight. High levels of sodium may also aggravate high blood pressure once it exists. To prevent or reduce high blood pressure, a low sodium diet is usually recommended, along with exercise and weight control. Medication may also be recommended to reduce blood pressure.

To lower the amount of sodium consumed, a person usually needs to reduce the most concentrated form of sodium, table salt, and foods that contain high levels of salt. One teaspoon of salt has 2000 mg of sodium. Cured meat has about 350 mg per serving, while fresh meat, poultry or fish have only about 75 mg per serving. Milk has 125 mg per cup, fresh vegetables have about 35 mg per serving, and fresh fruits have less than 10 mg per serving. Thus, a diet high in fresh fruits and vegetables, with moderate amounts of milk and meat or poultry, is quite low in sodium.

The amount of sodium in water is only a health concern when the sodium level is high or when the person's ability to handle sodium decreases. In areas where water is soft and sodium levels are 20 mg per liter or less, people probably do not need to be concerned about the sodium in water. At this level, water will contribute only about 1% of the sodium in an average diet, or 40 to 50 mg sodium per day—not much in a diet that contains 2000 mg of sodium.

However, as the amount of sodium in water increases, or as a person's tolerance to sodium decreases, the need to be concerned about the sodium in drinking water increases. People who live in areas with high sodium levels in drinking water generally have higher blood pressure than people who live in areas with lower sodium levels in drinking water.

The Environmental Protection Agency suggests 20 mg or less of sodium per liter as the amount of sodium to strive for in drlnking water. The natural sodium content of water, however, varies from 0 to over 500 mg per liter (a liter is about one quart), averaging 17 mg per liter.

In Washington, water from wells near the ocean or Puget Sound often have a high level of sodium because of salt water intrusion. The sodium levels of wells in these areas can be 30 to 1000 mg per liter or more. Hard water from wells in eastern Washington may also have high levels of sodium because sodium is a common mineral that dissolves from soil.

If you are on a public water system and you are concerned about sodium in your water, you can call or write your local water company to ask how much sodium is in your water. The Washington State Department of Social and Health Services regularly tests public water systems for sodium and several other minerals.

If you have a private well or spring, you will need to have your water tested for sodium if this is a concern.

Sodium is added to water during the softening process. The worksheet at the end of this publication will help you calculate the amount of sodium in your home-softened water.

Hard water is caused by calcium and magnesium that are dissolved in the water. Hard water interferes with laundering, dishwashing, bathing, and personal grooming. When used with soap, hard water will cause soap deposits that do not dissolve. Hard water also affects appliances. For example, scale can build up in water heaters, causing them to malfunction.

Water is softened by passing it through a bed of ion-exchange resin which replaces the calcium and magnesium with sodium. Sodium makes the water feel slippery and thus, softened.

The calcium and magnesium which cause hardness are reported as grains per gallon, or milligrams per liter (mg/L), or parts per million (ppm). One grain per gallon equals 17.1 mg/ L or ppm. The following charts give the classification of water and an estimate of the amount of sodium added when water is softened.

The third chart below gives information on the relationship of sodium in diet and water.

The rule of thumb is for people on sodium-restricted diets to avoid using softened water. However, it is necessary to evaluate the level of sodium in the water, and how severe the sodium-restricted diet is before making a final decision about whether or not to use softened water.

Usually a house can be plumbed so that one faucet can use unsoftened water. Sometimes the water softener is placed on the water line going to the hot water tank, and the cold water line is left unsoftened. Thus, water going to the laundry and showers can be softened or partially softened, while water for drinking and cooking can be unsoftened.

Using bottled water is an alternative to using high sodium tap water at home, if the bottled water is low in sodium.

Caution: Bottled waters may come from springs, public water systems or private wells that have a high sodium content. Read the label.

If the bottled water is not labeled for sodium content, write to the company and ask for the information.

If sodium is a health issue for you, determine the sodium content of water you will be drinking, regardless of its source. Bottling does not affect the sodium content.

Spring water is water as it comes naturally from the ground. Some is low in sodium. But because spring water is groundwater, it can be high in sodium.

Mineral waters are also groundwater, commonly from mineral springs, and may contain high levels of sodium whether bottled or direct from the spring.

Drinking water. Water labeled "drinking water" is often taken from a public water supply and has as much sodium as the water system from which it was obtained.

Sodas and seltzers. Club soda usually has sodium added, while seltzers are low in sodium or sodium free.

Once in water, sodium is difficult to remove. Distillation and reverse osmosis are methods that can be used, but they are slow and produce only small quantities of water. You can treat drinking water by these means, but compare the cost to low-sodium bottled water or another source.

By Sue N. Butkus, M. S., R. D., Extension Nutrition Specialist, Washington State University Puyallup Research and Extension Center; and Ronald E. Hermanson, Ph. D., P. E., Extension Agricultural Engineer, Washington State University, Pullman.

Issued by Washington State University Cooperative Extension and the U.S. Department of Agriculture in furtherance of the Acts of May 8 and June 30, 1914. Cooperative Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, color, gender, national origin, religion, age, disability, and sexual orientation. Evidence of noncompliance may be reported through your local Cooperative Extension office. Trade names have been used to simplify information; no endorsement is intended. Published June 1989. Subject code 376. A. EB1525