Water hardness data
The hardest water cities in America
The hardest water cities in America get ranked constantly, and most of those rankings are compiled from other rankings. The numbers drift and the sources vanish, until cities end up tagged with figures their own utilities never published. This ranking works from the utility's own records. Each city below links to its full report, and each report shows its source and the date we last checked it.
Hardness is measured in parts per million of dissolved calcium and magnesium. Above 121 ppm counts as hard under the US Geological Survey scale. Above 180 ppm counts as very hard. Twenty-three of the 25 cities here clear the hard line, and eleven clear very hard.
This ranking covers the cities in our verified dataset, not every city in America. A city missing from the list may still have hard water. We add cities as we verify them against primary utility sources, and we leave out any figure we can't confirm.
| Rank | City | State | Hardness (ppm) | Grains/gal | Band |
|---|---|---|---|---|---|
| 1 | San Jose | CA | 350 | 20.5 | Hard to Very hard |
| 2 | Madison | WI | 339 | 19.8 | Very hard |
| 3 | Indianapolis | IN | 317 | 18.5 | Very hard |
| 4 | San Antonio | TX | 299 | 17.5 | Very hard |
| 5 | Las Vegas | NV | 291 | 17.0 | Very hard |
| 5 | Mesa | AZ | 291 | 17.0 | Very hard |
| 7 | San Diego | CA | 276 | 16.1 | Very hard |
| 8 | Scottsdale | AZ | 274 | 16.0 | Very hard |
| 9 | Jacksonville | FL | 246 | 14.4 | Hard to Very hard |
| 10 | Phoenix | AZ | 237 | 13.9 | Hard to Very hard |
| 11 | Tampa | FL | 185 | 10.8 | Very hard |
| 12 | El Paso | TX | 175 | 10.2 | Hard |
| 13 | Omaha | NE | 170 | 9.9 | Hard |
| 13 | Wichita | KS | 170 | 9.9 | Hard |
| 15 | Dayton | OH | 155 | 9.1 | Hard |
| 16 | Des Moines | IA | 150 | 8.8 | Hard |
| 17 | Cincinnati | OH | 142 | 8.3 | Hard |
| 18 | Chicago | IL | 139 | 8.1 | Hard |
| 19 | Beavercreek | OH | 137 | 8.0 | Hard |
| 20 | Milwaukee | WI | 136 | 8.0 | Hard |
| 21 | Fresno | CA | 129 | 7.5 | Hard |
| 21 | Orlando | FL | 129 | 7.5 | Hard |
| 23 | Louisville | KY | 128 | 7.5 | Hard |
| 24 | Cleveland | OH | 120 | 7.0 | Moderately hard |
| 24 | Columbus | OH | 120 | 7.0 | Moderately hard |
How we verify the hardest water cities
Each figure comes from the city utility's own published water quality data. That means the annual water quality report, the utility's hardness page, or its published FAQ. We do not use aggregator sites, plumber blogs, or other rankings as sources.
Where a utility publishes a range, we use the midpoint and show the range on the city's report page. Where a utility publishes grains per gallon, we convert at 17.1 ppm per grain. When we re-check a figure, the city's page shows the verification date. The full process is documented on our methodology page.
Some cities can't be verified this way. Chicago, for example, publishes its water quality data in formats we can't confirm in text. Cities like that stay in our dataset with their last known figure and no verification date.
Why published hardness numbers disagree
The wrong-number problem is simple to state: the hardness figures published online for a given city often disagree with each other, and sometimes disagree with the utility itself.
Three examples from our own verification work, checked in August 2026. The Las Vegas Valley Water District's website answered "how hard is our water" with 291 ppm while a second block on the same page still said 280. San Diego's utility page stated its range as 272 to 284 ppm and also as 16 to 18 grains per gallon, which converts to 274 to 308. Both can't be right. And the Chicago documents we checked, the comprehensive chemical analysis and the current water quality report, are scanned images with no machine-readable text, which is part of why aggregator sites guess.
None of this is scandal. Utilities update pages unevenly and hardness genuinely varies by season and source. But it means a number copied from a ranking that copied it from another ranking has usually drifted from anything a utility ever measured. It's why every figure here traces to a primary source you can click. The pattern has a name and its own page: the wrong-number problem.
What city has the hardest water in the US?
In our verified dataset, San Jose, California tops the list at 350 ppm. The figure comes from the utility's own published data, and the city's report page shows the source.
Is hard water dangerous to drink?
No. Calcium and magnesium in drinking water pose no health risk, and both are minerals your body uses. The problems hard water causes are practical: scale in pipes and appliances, and the dry skin and hair that follow every shower.
What ppm is considered hard water?
The US Geological Survey scale counts 121 to 180 ppm as hard and anything above 180 ppm as very hard. Below 60 ppm counts as soft. Eleven of the 25 cities on this list sit above 180 ppm.
How can I check the water hardness in my area?
Enter your zip code in our lookup tool and you'll get your area's figure with its source. For your own tap, a hardness test strip from any hardware store gives you a reading in about thirty seconds.
Why does my utility's number differ from other websites?
Most hardness sites copy from each other rather than from utilities, and copied numbers drift. Utilities also publish ranges, seasonal figures, and different units, which get flattened or misconverted along the way. When in doubt, the utility's current published figure wins.