Well water hardness by state and county
Millions of American households drink water from their own well. No utility tests that water and no water quality report covers it. These pages summarise the hardness the U.S. Geological Survey measured in wells county by county, so you know what to expect before you test your own well.
- Test a private well every year for total coliform bacteria, nitrates, total dissolved solids and pH; test more often if young children, older adults or a pregnant or nursing person live in the home. (US EPA, Protect Your Home's Water)
- Test at least once a year and ask the local health department which other germs or chemicals matter where you live. (CDC, Guidelines for Testing Well Water)
States covered so far
| Alabama | 12 counties | 3.4 gpg | soft |
| Alaska | 6 counties | 7.3 gpg | hard |
| Arizona | 15 counties | 11.2 gpg | very hard |
| Arkansas | 19 counties | 8.6 gpg | hard |
| California | 52 counties | 9 gpg | hard |
| Colorado | 34 counties | 9.2 gpg | hard |
| Connecticut | 6 counties | 4.7 gpg | moderately hard |
| Delaware | 3 counties | 3.3 gpg | soft |
| Florida | 33 counties | 11.9 gpg | very hard |
| Georgia | 19 counties | 5.7 gpg | moderately hard |
| Hawaii | 4 counties | 3.8 gpg | moderately hard |
| Idaho | 44 counties | 8.3 gpg | hard |
| Illinois | 22 counties | 19 gpg | very hard |
| Indiana | 19 counties | 17.5 gpg | very hard |
| Iowa | 72 counties | 19.5 gpg | very hard |
| Kansas | 53 counties | 17.2 gpg | very hard |
| Kentucky | 6 counties | 14.5 gpg | very hard |
| Louisiana | 48 counties | 4.6 gpg | moderately hard |
| Maine | 14 counties | 2.8 gpg | soft |
| Maryland | 23 counties | 3.7 gpg | moderately hard |
| Massachusetts | 9 counties | 2.9 gpg | soft |
| Michigan | 38 counties | 17.3 gpg | very hard |
| Minnesota | 41 counties | 15.9 gpg | very hard |
| Mississippi | 23 counties | 1.5 gpg | soft |
| Missouri | 19 counties | 14.7 gpg | very hard |
| Montana | 38 counties | 12.3 gpg | very hard |
| Nebraska | 54 counties | 14.8 gpg | very hard |
| Nevada | 15 counties | 8.3 gpg | hard |
| New Hampshire | 10 counties | 3.3 gpg | soft |
| New Jersey | 20 counties | 5.1 gpg | moderately hard |
| New Mexico | 20 counties | 9.5 gpg | hard |
| New York | 55 counties | 9.3 gpg | hard |
| North Carolina | 26 counties | 4.2 gpg | moderately hard |
| North Dakota | 36 counties | 15.7 gpg | very hard |
| Ohio | 35 counties | 19.2 gpg | very hard |
| Oklahoma | 24 counties | 15.4 gpg | very hard |
| Oregon | 14 counties | 6 gpg | moderately hard |
| Pennsylvania | 48 counties | 6.4 gpg | moderately hard |
| Rhode Island | 2 counties | 1.4 gpg | soft |
| South Carolina | 16 counties | 2.5 gpg | soft |
| South Dakota | 40 counties | 18 gpg | very hard |
| Tennessee | 18 counties | 7.7 gpg | hard |
| Texas | 43 counties | 12.3 gpg | very hard |
| Utah | 24 counties | 15.4 gpg | very hard |
| Vermont | 3 counties | 7 gpg | hard |
| Virginia | 26 counties | 3.6 gpg | moderately hard |
| Washington | 30 counties | 5.4 gpg | moderately hard |
| West Virginia | 26 counties | 5.1 gpg | moderately hard |
| Wisconsin | 28 counties | 13.9 gpg | very hard |
| Wyoming | 21 counties | 11.9 gpg | very hard |