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Water Hardness

San Diego has relatively hard water, as do more than 85 percent of American homes. We import most of our water, and as the water travels through rock and soil, it picks up minerals, including calcium and magnesium. These minerals produce what is often referred to as “hardness” in water, and what gives Southern California some of the hardest water in the country.

Typically, drinking water in San Diego averages about 15.4 grains per gallon (gr/gal) or 263 parts per million (ppm), and depending upon water demand and area of the City you live can range from 13.4 to 19.0 gr/gal or 229 to 325 ppm.

Each year, the City publishes the annual “Drinking Water Quality Report” that is mailed to all addresses in San Diego. In this report, among other data about your water, you will find details about water hardness measured at each of the City’s three water treatment plants. The latest report, and previous issues, can be found on the Water Quality page.