Well water hardness in Idaho
Across 44 counties of Idaho, the median well sampled by the USGS has 8.3 gpg of hardness. Counties range from 1.7 gpg (Valley County) to 23 gpg (Caribou 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.
Counties, hardest first
| gpg | mg/L | wells | ||
|---|---|---|---|---|
| Caribou County | 23 | 394 | 44 | very hard |
| Oneida County | 19 | 326 | 28 | very hard |
| Franklin County | 18 | 309 | 18 | very hard |
| Bear Lake County | 17.2 | 295 | 28 | very hard |
| Minidoka County | 16.1 | 275 | 115 | very hard |
| Twin Falls County | 15.9 | 272 | 214 | very hard |
| Bannock County | 15.5 | 266 | 75 | very hard |
| Jerome County | 13.6 | 233 | 108 | very hard |
| Cassia County | 13.5 | 232 | 130 | very hard |
| Bonneville County | 13.4 | 230 | 41 | very hard |
| Power County | 13.1 | 225 | 81 | very hard |
| Bingham County | 12.5 | 214 | 168 | very hard |
| Payette County | 11.3 | 193 | 45 | very hard |
| Teton County | 10.9 | 186 | 18 | very hard |
| Canyon County | 10.7 | 183 | 255 | very hard |
| Butte County | 10.4 | 178 | 276 | hard |
| Jefferson County | 10.2 | 174 | 88 | hard |
| Madison County | 9.9 | 170 | 28 | hard |
| Blaine County | 9.8 | 168 | 79 | hard |
| Gooding County | 9.6 | 165 | 72 | hard |
| Custer County | 8.6 | 147 | 46 | hard |
| Washington County | 8.4 | 143 | 43 | hard |
| Lincoln County | 8.2 | 141 | 48 | hard |
| Lemhi County | 8.1 | 139 | 33 | hard |
| Clark County | 8 | 137 | 37 | hard |
| Lewis County | 7.9 | 135 | 20 | hard |
| Ada County | 7.5 | 128 | 343 | hard |
| Boundary County | 7.1 | 122 | 23 | hard |
| Latah County | 6.7 | 116 | 48 | moderately hard |
| Fremont County | 6.7 | 114 | 63 | moderately hard |
| Nez Perce County | 6.5 | 112 | 38 | moderately hard |
| Clearwater County | 6.3 | 109 | 17 | moderately hard |
| Bonner County | 5.9 | 101 | 73 | moderately hard |
| Kootenai County | 5.8 | 100 | 60 | moderately hard |
| Idaho County | 5.5 | 95 | 45 | moderately hard |
| Gem County | 5.2 | 89 | 82 | moderately hard |
| Owyhee County | 5.2 | 89 | 146 | moderately hard |
| Elmore County | 5 | 85 | 142 | moderately hard |
| Benewah County | 4.8 | 83 | 43 | moderately hard |
| Adams County | 3.2 | 55 | 18 | soft |
| Camas County | 3.2 | 54 | 14 | soft |
| Shoshone County | 2.6 | 44 | 29 | soft |
| Boise County | 2 | 34 | 24 | soft |
| Valley County | 1.7 | 28 | 56 | soft |
Counties with fewer than 10 sampled wells, or a median outside 5–500 mg/L, are not shown until the figure is reviewed.
Idaho: tap water hardness by city → · Well water hardness by state and county →