Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Oxford | Maine | 134 | 40,326 | 8,473 |
| Clinton | Iowa | 28 | 40,325 | 1,996 |
| Chisago | Minnesota | 110 | 40,252 | 932 |
| Columbia | Oregon | 56 | 40,231 | 9,494 |
| Callaway | Missouri | 15 | 40,194 | 568 |
| Meade | Kentucky | 5 | 40,164 | 739 |
| Douglas | Washington | 46 | 40,088 | 3,795 |
| Barren | Kentucky | 2 | 40,030 | 433 |
| Independence | Arkansas | 14 | 39,969 | 409 |
| Jackson | Indiana | 10 | 39,956 | 1,373 |
| Nez Perce | Idaho | 25 | 39,929 | 1,887 |
| McKean | Pennsylvania | 57 | 39,915 | 10,602 |
| San Juan | Washington | 112 | 39,901 | 6,963 |
| Bonner | Idaho | 152 | 39,891 | 5,382 |
| Matagorda | Texas | 44 | 39,885 | 2,829 |
| Jefferson Davis Parish | Louisiana | 9 | 39,880 | 293 |
| Cerro Gordo | Iowa | 34 | 39,879 | 3,147 |
| Hatillo Municipio | Puerto Rico | 6 | 39,785 | 1,383 |
| Alexander | North Carolina | 26 | 39,643 | 1,033 |
| Bryan | Oklahoma | 13 | 39,612 | 3,370 |
| Union | Arkansas | 27 | 39,601 | 1,255 |
| Llano | Texas | 27 | 39,555 | 3,428 |
| Habersham | Georgia | 17 | 39,521 | 537 |
| Darke | Ohio | 73 | 39,493 | 4,784 |
| Gadsden | Florida | 26 | 39,434 | 511 |
| Sabine Parish | Louisiana | 20 | 39,370 | 5,485 |
| Bryan | Georgia | 56 | 39,333 | 1,954 |
| Emmet | Michigan | 206 | 39,314 | 4,007 |
| Franklin | New York | 89 | 39,157 | 3,172 |
| Baxter | Arkansas | 55 | 39,134 | 2,535 |
| Gratiot | Michigan | 79 | 39,129 | 2,042 |
| Muscatine | Iowa | 38 | 39,113 | 2,700 |
| Monroe | Wisconsin | 97 | 39,109 | 2,390 |
| Wise | Virginia | 9 | 39,101 | 510 |
| Polk | Georgia | 4 | 39,086 | 83 |
| White | Tennessee | 5 | 39,069 | 181 |
| Chippewa | Michigan | 135 | 39,020 | 2,487 |
| Montgomery | New York | 53 | 38,998 | 7,678 |
| Alcorn | Mississippi | 8 | 38,985 | 4,326 |
| Crawford | Kansas | 18 | 38,940 | 1,282 |
| Tioga | New York | 95 | 38,898 | 4,212 |
| Franklin | Alabama | 6 | 38,739 | 266 |
| Henry | Indiana | 57 | 38,738 | 3,136 |
| Stephens | Oklahoma | 10 | 38,695 | 2,002 |
| Sampson | North Carolina | 51 | 38,676 | 2,100 |
| Sioux | Iowa | 16 | 38,650 | 698 |
| Butts | Georgia | 7 | 38,630 | 191 |
| Dyer | Tennessee | 6 | 38,565 | 183 |
| Marshall | Indiana | 87 | 38,429 | 12,645 |
| Bradford | Pennsylvania | 90 | 38,386 | 17,973 |
| Williams | North Dakota | 22 | 38,366 | 564 |
| Albany | Wyoming | 24 | 38,088 | 740 |
| Brown | South Dakota | 21 | 38,081 | 1,750 |
| Park | Wyoming | 49 | 38,068 | 951 |
| Davie | North Carolina | 6 | 37,844 | 457 |
| County 06001 | 06 | 7 | 37,732 | 204 |
| Bolivar | Mississippi | 29 | 37,727 | 11,980 |
| Fayette | West Virginia | 12 | 37,599 | 1,759 |
| Patillas Municipio | Puerto Rico | 12 | 37,543 | 6,428 |
| Marshall | Kentucky | 6 | 37,506 | 1,276 |
| Cocke | Tennessee | 8 | 37,426 | 152 |
| Pike | Mississippi | 17 | 37,313 | 5,877 |
| Currituck | North Carolina | 17 | 37,279 | 2,054 |
| Clark | Kentucky | 2 | 37,189 | 315 |
| Barbour | Alabama | 10 | 37,158 | 714 |
| Glenn | California | 35 | 37,146 | 349 |
| San Sebastian Municipio | Puerto Rico | 5 | 36,986 | 1,552 |
| Tift | Georgia | 14 | 36,945 | 415 |
| Franklin | Vermont | 82 | 36,880 | 7,456 |
| Boyle | Kentucky | 2 | 36,861 | 417 |
| Pontotoc | Oklahoma | 11 | 36,830 | 615 |
| Brooke | West Virginia | 8 | 36,770 | 1,190 |
| Caldwell | Texas | 8 | 36,730 | 487 |
| Sandusky | Ohio | 54 | 36,728 | 2,942 |
| Columbus | North Carolina | 64 | 36,725 | 4,479 |
| Pontotoc | Mississippi | 12 | 36,687 | 8,037 |
| Shelby | Ohio | 42 | 36,662 | 2,731 |
| Mower | Minnesota | 54 | 36,656 | 630 |
| Bingham | Idaho | 74 | 36,624 | 3,178 |
| Arroyo Municipio | Puerto Rico | 1 | 36,606 | 561 |
| Accomack | Virginia | 88 | 36,603 | 4,602 |
| Clinton | Michigan | 94 | 36,557 | 3,263 |
| McNairy | Tennessee | 5 | 36,536 | 135 |
| Stark | North Dakota | 8 | 36,506 | 136 |
| Waupaca | Wisconsin | 208 | 36,502 | 3,818 |
| Jackson | Ohio | 6 | 36,458 | 724 |
| Humacao Municipio | Puerto Rico | 2 | 36,433 | 296 |
| Morgan | Illinois | 18 | 36,402 | 856 |
| Mecosta | Michigan | 165 | 36,359 | 5,579 |
| Lincoln | New Mexico | 52 | 36,231 | 6,263 |
| Muhlenberg | Kentucky | 5 | 36,058 | 429 |
| Steele | Minnesota | 36 | 36,022 | 441 |
| Lafayette | Missouri | 15 | 36,005 | 864 |
| Titus | Texas | 6 | 35,946 | 180 |
| Lee | Iowa | 7 | 35,911 | 708 |
| Cherokee | Oklahoma | 37 | 35,853 | 9,781 |
| Cass | Michigan | 152 | 35,835 | 3,671 |
| Lincoln | South Dakota | 8 | 35,801 | 350 |
| Kandiyohi | Minnesota | 74 | 35,789 | 1,003 |
| Allegany | New York | 78 | 35,785 | 6,609 |