Well water hardness in Washington
Across 30 counties of Washington, the median well sampled by the USGS has 5.4 gpg of hardness. Counties range from 2.3 gpg (Pacific County) to 13.2 gpg (Franklin 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 | ||
|---|---|---|---|---|
| Franklin County | 13.2 | 226 | 158 | very hard |
| Island County | 11.1 | 190 | 81 | very hard |
| Grant County | 10.5 | 180 | 146 | very hard |
| San Juan County | 9.9 | 170 | 55 | hard |
| Benton County | 8.8 | 150 | 178 | hard |
| Walla Walla County | 8.8 | 150 | 31 | hard |
| Garfield County | 8.1 | 140 | 10 | hard |
| Yakima County | 8 | 137 | 215 | hard |
| Skagit County | 7.5 | 129 | 52 | hard |
| Whitman County | 7 | 120 | 94 | hard |
| Whatcom County | 6.5 | 112 | 224 | moderately hard |
| Lincoln County | 6.5 | 112 | 62 | moderately hard |
| Kittitas County | 5.6 | 96 | 49 | moderately hard |
| Spokane County | 5.5 | 94 | 69 | moderately hard |
| Klickitat County | 5.4 | 92 | 38 | moderately hard |
| Okanogan County | 5.4 | 92 | 24 | moderately hard |
| Adams County | 5.4 | 92 | 89 | moderately hard |
| Stevens County | 5.3 | 91 | 43 | moderately hard |
| Douglas County | 5.1 | 87 | 23 | moderately hard |
| Cowlitz County | 4.2 | 72 | 46 | moderately hard |
| Kitsap County | 4.2 | 72 | 255 | moderately hard |
| Clark County | 4.1 | 70 | 90 | moderately hard |
| Snohomish County | 4.1 | 70 | 308 | moderately hard |
| King County | 3.8 | 65 | 365 | moderately hard |
| Pierce County | 3.3 | 57 | 229 | soft |
| Grays Harbor County | 3.3 | 57 | 28 | soft |
| Thurston County | 3.1 | 54 | 394 | soft |
| Mason County | 2.6 | 45 | 27 | soft |
| Lewis County | 2.6 | 45 | 23 | soft |
| Pacific County | 2.3 | 39 | 51 | soft |
Counties with fewer than 10 sampled wells, or a median outside 5–500 mg/L, are not shown until the figure is reviewed.
Washington: tap water hardness by city → · Well water hardness by state and county →