Water hardness in Utah
Utah has a median ambient water hardness of 272 mg/L, which is 15.9 grains per gallon and classes as very hard. That is the middle of 139,440 samples across 29 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 Utah
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 |
|---|---|---|---|---|---|
| Emery County | 690 | 40.3 | Very hard | 300 to 1,200 | 10,497 |
| Millard County | 458 | 26.8 | Very hard | 304 to 680 | 2,796 |
| Grand County | 380 | 22.2 | Very hard | 250 to 530 | 6,988 |
| Juab County | 378 | 22.1 | Very hard | 223 to 460 | 2,289 |
| Sanpete County | 367 | 21.4 | Very hard | 250 to 485 | 2,505 |
| Kane County | 346 | 20.2 | Very hard | 256 to 640 | 4,124 |
| Salt Lake County | 337 | 19.7 | Very hard | 206 to 488 | 12,687 |
| Wayne County | 334 | 19.5 | Very hard | 224 to 663 | 2,437 |
| Box Elder County | 323 | 18.9 | Very hard | 250 to 486 | 5,376 |
| Tooele County | 320 | 18.7 | Very hard | 218 to 615 | 2,110 |
| Uintah County | 320 | 18.7 | Very hard | 190 to 640 | 11,023 |
| Davis County | 310 | 18.1 | Very hard | 198 to 434 | 4,676 |
| San Juan County | 290 | 16.9 | Very hard | 188 to 420 | 7,844 |
| Washington County | 290 | 16.9 | Very hard | 200 to 605 | 3,754 |
| Carbon County | 289 | 16.9 | Very hard | 208 to 618 | 3,214 |
| Utah County | 264 | 15.4 | Very hard | 195 to 350 | 9,813 |
| Daggett County | 250 | 14.6 | Very hard | 210 to 280 | 1,895 |
| Iron County | 240 | 14 | Very hard | 180 to 410 | 1,666 |
| Morgan County | 240 | 14 | Very hard | 205 to 272 | 1,873 |
| Rich County | 240 | 14 | Very hard | 196 to 284 | 839 |
| Cache County | 235 | 13.7 | Very hard | 195 to 293 | 5,282 |
| Duchesne County | 220 | 12.9 | Very hard | 107 to 279 | 5,725 |
| Sevier County | 201 | 11.7 | Very hard | 88 to 338 | 2,961 |
| Garfield County | 198 | 11.6 | Very hard | 139 to 264 | 5,042 |
| Piute County | 192 | 11.2 | Very hard | 152 to 216 | 1,552 |
| Weber County | 192 | 11.2 | Very hard | 140 to 240 | 2,311 |
| Beaver County | 191 | 11.2 | Very hard | 109 to 304 | 2,609 |
| Summit County | 188 | 11 | Very hard | 75 to 285 | 6,458 |
| Wasatch County | 166 | 9.7 | Hard | 113 to 223 | 9,094 |
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 Utah
At 15.9 grains per gallon, a family of four would need a softener of about 40,000 grains to regenerate roughly weekly, using around 648 lb of salt a year. Size it for your own household.
28 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.