Ranked list of the 10 hardest water cities in America by ppm, from San Jose CA at 350 to Phoenix AZ at 237. Source: MyApartmentWaterQuality.com.

New York, NY - September 22, 2026 - MyApartmentWaterQuality.com has published a new ranking of the hardest water cities in America. Every number in it comes from the city utility that pumps the water.

San Jose, CA ranks first at 350 ppm, followed by Madison, WI at 339 ppm and Indianapolis, IN at 317 ppm, according to verified utility data compiled by MyApartmentWaterQuality.com. All three sit far above the federal line for "very hard" water.

Hardness is the amount of calcium and magnesium dissolved in tap water. The minerals are safe to drink, but they're the reason kettles scale, faucets crust white, hair dries stiff, and skin feels tight after a shower.

That "very hard" line comes from the U.S. Geological Survey, which measures hardness in parts per million. Anything past 180 counts as very hard, and all 10 cities at the top of the list are above it. So are 23 of the 25 in the full ranking. Anyone can check their own city on the list or look up their zip code with the site's free tool.

The full top 10:

1. San Jose, CA — 350 ppm

2. Madison, WI — 339 ppm

3. Indianapolis, IN — 317 ppm

4. San Antonio, TX — 299 ppm

5. Las Vegas, NV — 291 ppm (tie)

5. Mesa, AZ — 291 ppm (tie)

7. San Diego, CA — 276 ppm

8. Scottsdale, AZ — 274 ppm

9. Jacksonville, FL — 246 ppm

10. Phoenix, AZ — 237 ppm

Arizona places three cities in the top 10 and California places two, but the highest-ranked city east of the Mississippi is Madison at number two.

Hardness rankings are easy to find online but hard to trust. Most copy their numbers from other rankings, and the figures drift until they no longer match anything a utility measured. The site calls this the wrong-number problem.

This ranking skips the middlemen. If a utility never published a number, that number stays out. Any figure that can't be confirmed is labeled estimated and excluded, and cities that report a range enter at the midpoint. Each city page links to the document its number came from, along with the date it was last checked.

"Most hardness numbers online are copies of copies," said a spokesperson for MyApartmentWaterQuality.com. "We publish what the utility itself has published, and we link to it so anyone can check us."

The complete ranking is at https://www.myapartmentwaterquality.com/hardest-water-cities. The lookup tool is free.

About MyApartmentWaterQuality.com

MyApartmentWaterQuality.com is a water hardness lookup and research site, a GRN Labs property. The site reports local hardness levels by zip code, using USGS data and the water quality reports that utilities publish. It keeps hardness profiles for 40 U.S. water systems and has verified 25 of them against the utility's own figures, while in the process of verifying more. Its methods are public.

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