Water Hardness by ZIP Code

85% of US Homes Have Hard Water — Is Yours One of Them?

Hard water is the single most common water quality issue in the United States. According to US Geological Survey data, 85% of American homes receive water that contains dissolved calcium and magnesium above the "moderately hard" threshold. Yet most homeowners don't know their local hardness level — or the annual cost it adds to their energy and maintenance bills.

The Southwest and Mountain West are the hardest regions: Las Vegas, Phoenix, San Antonio, Salt Lake City, and Tucson all report hardness above 250 mg/L. The Pacific Northwest, New England, and parts of the Southeast tend to have softer water. But even within a single city, hardness can vary by ZIP code depending on which treatment plant serves that area.

US Water Hardness by Region

What Does Hard Water Cost American Households?

The US Department of Energy estimates that a 1.5mm limescale layer on a water heater element increases energy consumption by 7–10%. For an average American household, hard water adds an estimated $400–$800 per year in excess energy costs, appliance maintenance, and increased detergent use. In very hard water areas like Las Vegas or Phoenix, this figure can reach $1,200–$1,500 annually.

Tools for Your Hardness Level