Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Scott | Kentucky | 1 | 35,714 | 114 |
| Dunklin | Missouri | 13 | 35,654 | 1,384 |
| Knox | Ohio | 42 | 35,651 | 2,660 |
| Clarke | Alabama | 8 | 35,610 | 584 |
| Poinsett | Arkansas | 11 | 35,587 | 275 |
| Ascension Parish | Louisiana | 29 | 35,581 | 2,477 |
| Chambers | Alabama | 5 | 35,558 | 282 |
| Cidra Municipio | Puerto Rico | 5 | 35,537 | 1,165 |
| Jackson | North Carolina | 112 | 35,533 | 10,421 |
| Uintah | Utah | 24 | 35,486 | 1,247 |
| Lee | Illinois | 67 | 35,434 | 2,736 |
| Giles | Tennessee | 6 | 35,434 | 432 |
| De Soto Parish | Louisiana | 12 | 35,429 | 2,418 |
| San Lorenzo Municipio | Puerto Rico | 17 | 35,423 | 3,795 |
| Grant | Arkansas | 10 | 35,368 | 83 |
| Butler | Missouri | 14 | 35,253 | 1,027 |
| Marion | Alabama | 9 | 35,190 | 483 |
| Clarion | Pennsylvania | 46 | 35,183 | 4,949 |
| Simpson | Mississippi | 16 | 35,130 | 8,704 |
| Colusa | California | 29 | 35,121 | 273 |
| Ponce Municipio | Puerto Rico | 21 | 35,111 | 7,284 |
| Cowley | Kansas | 16 | 35,090 | 851 |
| Greene | Indiana | 8 | 35,077 | 1,134 |
| Beltrami | Minnesota | 188 | 34,995 | 1,040 |
| Washington Parish | Louisiana | 34 | 34,966 | 2,394 |
| Wayne | West Virginia | 10 | 34,878 | 1,215 |
| Lincoln | Mississippi | 10 | 34,845 | 3,387 |
| Grady | Oklahoma | 31 | 34,818 | 16,093 |
| Door | Wisconsin | 454 | 34,700 | 19,310 |
| Douglas | Wisconsin | 189 | 34,631 | 2,120 |
| Oconee | Georgia | 24 | 34,625 | 698 |
| Ford | Kansas | 9 | 34,610 | 723 |
| Auglaize | Ohio | 31 | 34,600 | 1,251 |
| McKinley | New Mexico | 28 | 34,524 | 3,979 |
| Cheboygan | Michigan | 181 | 34,486 | 3,537 |
| Stephenson | Illinois | 47 | 34,482 | 3,740 |
| Jefferson | Indiana | 11 | 34,443 | 496 |
| McCreary | Kentucky | 1 | 34,439 | 83 |
| Clinton | Illinois | 29 | 34,401 | 994 |
| Erath | Texas | 31 | 34,401 | 4,926 |
| Elk | Pennsylvania | 29 | 34,393 | 3,650 |
| Madison | Nebraska | 25 | 34,386 | 573 |
| Montgomery | Kentucky | 6 | 34,363 | 1,193 |
| Logan | West Virginia | 10 | 34,333 | 2,382 |
| Ashland | Ohio | 50 | 34,329 | 2,922 |
| Marion | South Carolina | 6 | 34,320 | 69 |
| Rowan | Kentucky | 3 | 34,317 | 1,238 |
| Woodford | Illinois | 66 | 34,250 | 5,738 |
| Scott | Missouri | 18 | 34,223 | 1,233 |
| Jefferson | West Virginia | 43 | 34,217 | 14,377 |
| Fulton | Illinois | 36 | 34,209 | 2,468 |
| Jefferson | Illinois | 16 | 34,083 | 279 |
| Nye | Nevada | 96 | 33,987 | 5,864 |
| Laurens | Georgia | 34 | 33,948 | 1,219 |
| Ware | Georgia | 12 | 33,921 | 321 |
| Tillamook | Oregon | 63 | 33,756 | 4,704 |
| Houghton | Michigan | 46 | 33,702 | 1,247 |
| Stevens | Washington | 68 | 33,702 | 10,726 |
| Scott | Mississippi | 14 | 33,695 | 10,379 |
| Pacific | Washington | 38 | 33,692 | 3,844 |
| Sullivan | New Hampshire | 65 | 33,684 | 4,684 |
| Osage | Oklahoma | 30 | 33,607 | 16,200 |
| McDonough | Illinois | 24 | 33,540 | 2,854 |
| Marshall | Iowa | 12 | 33,539 | 591 |
| Panola | Mississippi | 31 | 33,531 | 10,060 |
| Somerset | Maine | 100 | 33,494 | 10,674 |
| Caroline | Virginia | 43 | 33,476 | 3,127 |
| Campbell | Virginia | 26 | 33,398 | 1,846 |
| Grenada | Mississippi | 17 | 33,387 | 6,872 |
| Harris | Georgia | 18 | 33,381 | 1,089 |
| Branch | Michigan | 82 | 33,322 | 1,931 |
| Washington | Iowa | 25 | 33,305 | 2,007 |
| Jasper | Illinois | 6 | 33,299 | 346 |
| County 06043 | 06 | 13 | 33,276 | 854 |
| Milam | Texas | 11 | 33,269 | 929 |
| Putnam | Florida | 113 | 33,216 | 6,247 |
| Tioga | Pennsylvania | 84 | 33,215 | 22,092 |
| Huron | Michigan | 104 | 33,191 | 1,612 |
| San Jacinto | Texas | 38 | 33,186 | 2,374 |
| Granville | North Carolina | 51 | 33,178 | 5,255 |
| Putnam | West Virginia | 4 | 33,110 | 161 |
| Tazewell | Virginia | 22 | 33,010 | 780 |
| Kleberg | Texas | 12 | 32,881 | 1,225 |
| Adams | Mississippi | 8 | 32,826 | 2,696 |
| Plumas | California | 110 | 32,794 | 1,590 |
| Sanpete | Utah | 38 | 32,759 | 7,185 |
| Boone | Iowa | 13 | 32,746 | 824 |
| Union Parish | Louisiana | 20 | 32,739 | 9,066 |
| Lincoln | Nebraska | 50 | 32,730 | 1,287 |
| Jasper | Texas | 26 | 32,632 | 1,664 |
| Overton | Tennessee | 4 | 32,628 | 211 |
| Webster | Iowa | 30 | 32,620 | 2,274 |
| Addison | Vermont | 71 | 32,619 | 8,234 |
| Leflore | Mississippi | 17 | 32,564 | 5,439 |
| Calloway | Kentucky | 20 | 32,563 | 3,677 |
| Nantucket | Massachusetts | 5 | 32,563 | 347 |
| Guernsey | Ohio | 14 | 32,470 | 1,556 |
| Howard | Texas | 9 | 32,403 | 1,034 |
| Dodge | Nebraska | 17 | 32,386 | 493 |
| Pierce | Wisconsin | 95 | 32,378 | 1,498 |