Water hardness in Colorado
Colorado has a median ambient water hardness of 160 mg/L, which is 9.3 grains per gallon and classes as hard. That is the middle of 225,747 samples across 64 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 Colorado
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 |
|---|---|---|---|---|---|
| Prowers County | 1,300 | 75.9 | Very hard | 920 to 1,600 | 895 |
| Bent County | 1,010 | 59 | Very hard | 710 to 1,457 | 1,935 |
| Kiowa County | 710 | 41.5 | Very hard | 440 to 1,100 | 156 |
| Sedgwick County | 680 | 39.7 | Very hard | 590 to 750 | 645 |
| Otero County | 672 | 39.3 | Very hard | 459 to 948 | 2,267 |
| Logan County | 650 | 38 | Very hard | 526 to 720 | 889 |
| Cheyenne County | 642 | 37.5 | Very hard | 170 to 1,006 | 111 |
| Morgan County | 570 | 33.3 | Very hard | 486 to 660 | 1,801 |
| Weld County | 550 | 32.1 | Very hard | 352 to 790 | 8,368 |
| Crowley County | 483 | 28.2 | Very hard | 358 to 749 | 177 |
| Delta County | 395 | 23.1 | Very hard | 153 to 660 | 5,795 |
| Washington County | 370 | 21.6 | Very hard | 186 to 630 | 69 |
| Montezuma County | 361 | 21.1 | Very hard | 160 to 970 | 5,518 |
| Montrose County | 340 | 19.9 | Very hard | 188 to 699 | 5,369 |
| Mesa County | 329 | 19.2 | Very hard | 236 to 550 | 9,322 |
| Pueblo County | 300 | 17.5 | Very hard | 198 to 417 | 4,744 |
| Rio Blanco County | 290 | 16.9 | Very hard | 168 to 520 | 7,613 |
| Baca County | 279 | 16.3 | Very hard | 200 to 490 | 268 |
| Lincoln County | 272 | 15.9 | Very hard | 220 to 402 | 39 |
| Arapahoe County | 266 | 15.5 | Very hard | 159 to 560 | 4,931 |
| Denver County | 260 | 15.2 | Very hard | 200 to 351 | 2,710 |
| Adams County | 237 | 13.8 | Very hard | 180 to 290 | 4,319 |
| Ouray County | 232 | 13.6 | Very hard | 125 to 312 | 4,666 |
| Las Animas County | 224 | 13.1 | Very hard | 140 to 734 | 2,035 |
| Huerfano County | 220 | 12.9 | Very hard | 130 to 410 | 868 |
| Garfield County | 210 | 12.3 | Very hard | 146 to 260 | 10,237 |
| San Miguel County | 198 | 11.6 | Very hard | 140 to 320 | 3,381 |
| Kit Carson County | 184 | 10.7 | Very hard | 141 to 200 | 123 |
| Moffat County | 180 | 10.5 | Hard | 128 to 250 | 4,845 |
| Yuma County | 180 | 10.5 | Hard | 160 to 200 | 836 |
| Pitkin County | 170 | 9.9 | Hard | 92 to 232 | 3,702 |
| La Plata County | 169 | 9.9 | Hard | 84 to 260 | 9,853 |
| El Paso County | 158 | 9.2 | Hard | 85 to 229 | 7,215 |
| Elbert County | 154 | 9 | Hard | 94 to 280 | 496 |
| Broomfield County | 150 | 8.8 | Hard | 120 to 250 | 9 |
| Routt County | 144 | 8.4 | Hard | 55 to 252 | 5,571 |
| Eagle County | 140 | 8.2 | Hard | 87 to 222 | 8,716 |
| Fremont County | 140 | 8.2 | Hard | 102 to 194 | 2,084 |
| Custer County | 140 | 8.2 | Hard | 120 to 160 | 478 |
| San Juan County | 134 | 7.8 | Hard | 64 to 217 | 4,369 |
| Teller County | 132 | 7.7 | Hard | 96 to 205 | 801 |
| Phillips County | 130 | 7.6 | Hard | 120 to 140 | 13 |
| Douglas County | 122 | 7.1 | Hard | 90 to 170 | 1,909 |
| Dolores County | 120 | 7 | Moderately hard | 86 to 280 | 366 |
| Jefferson County | 110 | 6.4 | Moderately hard | 58 to 188 | 4,533 |
| Park County | 100 | 5.8 | Moderately hard | 50 to 152 | 2,602 |
| Lake County | 91 | 5.3 | Moderately hard | 41 to 209 | 5,678 |
| Gilpin County | 90 | 5.3 | Moderately hard | 37 to 184 | 973 |
| Conejos County | 87 | 5.1 | Moderately hard | 53 to 130 | 3,089 |
| Jackson County | 86 | 5 | Moderately hard | 19 to 113 | 2,156 |
| Costilla County | 86 | 5 | Moderately hard | 64 to 119 | 601 |
| Summit County | 80 | 4.7 | Moderately hard | 60 to 116 | 3,232 |
| Gunnison County | 80 | 4.7 | Moderately hard | 51 to 118 | 7,042 |
| Alamosa County | 72 | 4.2 | Moderately hard | 56 to 95 | 906 |
| Archuleta County | 71 | 4.1 | Moderately hard | 40 to 134 | 2,206 |
| Clear Creek County | 69 | 4 | Moderately hard | 39 to 108 | 5,444 |
| Saguache County | 62 | 3.6 | Moderately hard | 42 to 110 | 1,342 |
| Chaffee County | 59 | 3.4 | Soft | 44 to 79 | 3,173 |
| Hinsdale County | 58 | 3.4 | Soft | 37 to 84 | 845 |
| Boulder County | 46 | 2.7 | Soft | 18 to 138 | 7,592 |
| Rio Grande County | 44 | 2.6 | Soft | 32 to 58 | 1,973 |
| Grand County | 40 | 2.3 | Soft | 24 to 78 | 8,826 |
| Mineral County | 31 | 1.8 | Soft | 21 to 42 | 1,235 |
| Larimer County | 18 | 1.1 | Soft | 5 to 110 | 21,785 |
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 Colorado
At 9.3 grains per gallon, a family of four would need a softener of about 24,000 grains to regenerate roughly weekly, using around 382 lb of salt a year. Size it for your own household.
64 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.