Water hardness in Oregon
Oregon has a median ambient water hardness of 50 mg/L, which is 2.9 grains per gallon and classes as soft. That is the middle of 54,035 samples across 36 counties.
This is ambient water, not tap water. These figures come from samples taken from wells, streams and springs by USGS, EPA and state agencies. Municipal utilities treat, blend and sometimes soften water before it reaches a tap, so a city supply can be considerably softer than the ground beneath it. Treat this as a good guide for a private well and an approximate one for city water. Your utility's annual water quality report gives the real number for a municipal tap, and a test strip gives it for yours.
Every monitored county in Oregon
Ranked hardest first. The middle 50% column shows how much the samples within a county vary, which matters more than the median where a county spans two geologies.
| County | mg/L | gpg | Class | Middle 50% | Samples |
|---|---|---|---|---|---|
| Malheur County | 277 | 16.2 | Very hard | 186 to 340 | 2,898 |
| Morrow County | 235 | 13.7 | Very hard | 151 to 361 | 1,229 |
| Umatilla County | 140 | 8.2 | Hard | 52 to 250 | 3,686 |
| Crook County | 121 | 7.1 | Hard | 82 to 172 | 405 |
| Grant County | 104 | 6.1 | Moderately hard | 77 to 151 | 416 |
| Baker County | 100 | 5.8 | Moderately hard | 67 to 187 | 523 |
| Gilliam County | 96 | 5.6 | Moderately hard | 83 to 156 | 356 |
| Jackson County | 84 | 4.9 | Moderately hard | 31 to 195 | 2,027 |
| Wheeler County | 76 | 4.4 | Moderately hard | 58 to 98 | 83 |
| Wasco County | 68 | 4 | Moderately hard | 42 to 85 | 957 |
| Sherman County | 66 | 3.9 | Moderately hard | 44 to 99 | 499 |
| Multnomah County | 65 | 3.8 | Moderately hard | 27 to 96 | 4,239 |
| Josephine County | 64 | 3.7 | Moderately hard | 40 to 110 | 1,460 |
| Washington County | 61 | 3.6 | Moderately hard | 37 to 95 | 2,736 |
| Harney County | 59 | 3.4 | Soft | 34 to 118 | 828 |
| Columbia County | 53 | 3.1 | Soft | 36 to 61 | 731 |
| Lake County | 52 | 3 | Soft | 39 to 72 | 387 |
| Marion County | 51 | 3 | Soft | 20 to 156 | 3,390 |
| Klamath County | 45 | 2.6 | Soft | 29 to 94 | 1,680 |
| Benton County | 44 | 2.6 | Soft | 24 to 120 | 1,525 |
| Jefferson County | 44 | 2.6 | Soft | 38 to 58 | 647 |
| Union County | 42 | 2.5 | Soft | 30 to 56 | 589 |
| Douglas County | 41 | 2.4 | Soft | 27 to 72 | 3,305 |
| Yamhill County | 39 | 2.3 | Soft | 25 to 97 | 2,224 |
| Curry County | 38 | 2.2 | Soft | 22 to 48 | 1,152 |
| Clatsop County | 34 | 2 | Soft | 17 to 76 | 719 |
| Coos County | 33 | 1.9 | Soft | 16 to 125 | 1,199 |
| Deschutes County | 31 | 1.8 | Soft | 20 to 56 | 1,510 |
| Clackamas County | 28 | 1.6 | Soft | 19 to 61 | 2,750 |
| Hood River County | 26 | 1.5 | Soft | 18 to 43 | 820 |
| Wallowa County | 26 | 1.5 | Soft | 21 to 104 | 481 |
| Polk County | 24 | 1.4 | Soft | 20 to 43 | 519 |
| Tillamook County | 23 | 1.3 | Soft | 18 to 32 | 1,299 |
| Lincoln County | 22 | 1.3 | Soft | 15 to 77 | 1,014 |
| Linn County | 21 | 1.2 | Soft | 15 to 48 | 1,851 |
| Lane County | 18 | 1.1 | Soft | 15 to 24 | 3,901 |
Source: Water Quality Portal (USGS, EPA and state agencies), waterqualitydata.us, retrieved 2026-09-19. 2,904,346 samples across 3,110 counties.
What this means for a household in Oregon
At 2.9 grains per gallon, a family of four would need a softener of about 16,000 grains to regenerate roughly weekly, using around 120 lb of salt a year. Size it for your own household.
36 of these counties include well samples, so the figures are a reasonable guide for private well water there. Municipal supplies in the same counties may be softer, because utilities often blend or treat.
Hardness follows geology rather than borders. Where a county sits on limestone or dolomite the water is hard; on granite, basalt or sandstone it is soft. That is why neighbouring counties in this table can differ by a factor of several.