Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Ashe | North Carolina | 36 | 7,150 | 4,805 |
| Humboldt | Iowa | 13 | 7,145 | 1,008 |
| Yellow Medicine | Minnesota | 13 | 7,133 | 208 |
| Beaver | Utah | 18 | 7,111 | 1,180 |
| Conejos | Colorado | 28 | 7,105 | 4,796 |
| Missaukee | Michigan | 51 | 7,094 | 1,908 |
| Quitman | Mississippi | 11 | 7,084 | 3,619 |
| Richland | Montana | 16 | 7,074 | 4,453 |
| Pierce | Georgia | 15 | 7,062 | 288 |
| Russell | Kansas | 12 | 7,053 | 1,272 |
| Brown | Kansas | 12 | 7,052 | 1,399 |
| Hancock | Kentucky | 4 | 7,024 | 726 |
| Phelps | Nebraska | 5 | 7,022 | 246 |
| Benewah | Idaho | 15 | 7,006 | 998 |
| Pulaski | Indiana | 33 | 7,005 | 2,379 |
| Lewis | Missouri | 5 | 7,002 | 150 |
| Dewey | South Dakota | 5 | 7,000 | 874 |
| San Augustine | Texas | 16 | 6,999 | 9,237 |
| Hamilton | Nebraska | 17 | 6,988 | 824 |
| Madison | Missouri | 9 | 6,987 | 403 |
| Yoakum | Texas | 5 | 6,975 | 1,487 |
| Washington | Idaho | 16 | 6,963 | 604 |
| Forest | Pennsylvania | 23 | 6,925 | 1,097 |
| Dillingham Census Area | Alaska | 24 | 6,913 | 10,869 |
| Alcona | Michigan | 69 | 6,907 | 667 |
| County NN037 | Navajo Nation | 13 | 6,907 | 2,385 |
| Jenkins | Georgia | 6 | 6,906 | 403 |
| Greenwood | Kansas | 10 | 6,900 | 2,339 |
| Clearwater | Idaho | 26 | 6,897 | 1,774 |
| Owyhee | Idaho | 25 | 6,879 | 1,299 |
| Hamlin | South Dakota | 6 | 6,877 | 434 |
| Wayne | Nebraska | 4 | 6,873 | 187 |
| Haskell | Oklahoma | 4 | 6,855 | 1,146 |
| Swift | Minnesota | 21 | 6,837 | 219 |
| Saguache | Colorado | 17 | 6,836 | 1,989 |
| Lavaca | Texas | 9 | 6,833 | 783 |
| County 09005 | 09 | 6 | 6,766 | 1,625 |
| Power | Idaho | 16 | 6,760 | 1,523 |
| Calhoun | Arkansas | 7 | 6,758 | 137 |
| Gentry | Missouri | 6 | 6,745 | 641 |
| Turner | Georgia | 6 | 6,741 | 428 |
| Delta | Texas | 4 | 6,725 | 200 |
| Real | Texas | 12 | 6,717 | 1,885 |
| Butte | Idaho | 15 | 6,713 | 246 |
| Wolfe | Kentucky | 2 | 6,700 | 493 |
| Doniphan | Kansas | 8 | 6,664 | 597 |
| Jackson | Minnesota | 13 | 6,655 | 179 |
| Monroe | West Virginia | 6 | 6,644 | 491 |
| Iron | Missouri | 23 | 6,622 | 1,154 |
| Shelby | Missouri | 5 | 6,620 | 109 |
| Grant | Kansas | 2 | 6,607 | 117 |
| Terrell | Georgia | 8 | 6,545 | 297 |
| Weston | Wyoming | 12 | 6,536 | 726 |
| Hudspeth | Texas | 8 | 6,521 | 1,659 |
| Meigs | Tennessee | 2 | 6,501 | 164 |
| Toole | Montana | 18 | 6,498 | 2,939 |
| McCulloch | Texas | 8 | 6,489 | 7,239 |
| Monona | Iowa | 14 | 6,465 | 1,080 |
| Holmes | Florida | 22 | 6,447 | 542 |
| Crawford | Georgia | 7 | 6,443 | 248 |
| Fall River | South Dakota | 14 | 6,440 | 1,994 |
| Clay | Kansas | 8 | 6,436 | 637 |
| Calhoun | Illinois | 7 | 6,434 | 347 |
| Talbot | Georgia | 5 | 6,415 | 512 |
| Searcy | Arkansas | 9 | 6,406 | 1,350 |
| Garza | Texas | 6 | 6,403 | 783 |
| Stewart | Georgia | 7 | 6,394 | 546 |
| Guadalupe | New Mexico | 12 | 6,387 | 1,505 |
| Jeff Davis | Georgia | 5 | 6,382 | 427 |
| Caldwell | Missouri | 8 | 6,371 | 928 |
| Concho | Texas | 4 | 6,322 | 3,245 |
| Lac qui Parle | Minnesota | 23 | 6,279 | 252 |
| Barton | Missouri | 4 | 6,279 | 271 |
| Morgan | Ohio | 15 | 6,267 | 969 |
| Caribou | Idaho | 18 | 6,259 | 1,092 |
| Hyde | North Carolina | 3 | 6,256 | 292 |
| Edwards | Illinois | 4 | 6,245 | 204 |
| Roberts | South Dakota | 11 | 6,241 | 1,527 |
| County 09071 | 09 | 6 | 6,234 | 478 |
| Pope | Illinois | 3 | 6,220 | 364 |
| Huerfano | Colorado | 13 | 6,202 | 1,921 |
| Yukon-Koyukuk Census Area | Alaska | 36 | 6,187 | 22,873 |
| Powell | Montana | 17 | 6,181 | 1,135 |
| Sublette | Wyoming | 28 | 6,181 | 2,695 |
| Calhoun | South Carolina | 11 | 6,171 | 253 |
| Dixie | Florida | 21 | 6,147 | 1,355 |
| Lafayette | Arkansas | 8 | 6,146 | 313 |
| Graham | North Carolina | 37 | 6,108 | 2,863 |
| Mitchell | Iowa | 16 | 6,105 | 1,360 |
| Thomas | Kansas | 7 | 6,104 | 424 |
| Pleasants | West Virginia | 3 | 6,071 | 129 |
| Valley | Montana | 13 | 6,060 | 1,915 |
| Wells | North Dakota | 6 | 6,057 | 378 |
| County 10033 | 10 | 2 | 6,050 | 178 |
| Lander | Nevada | 9 | 6,034 | 920 |
| Van Buren | Tennessee | 1 | 6,022 | 395 |
| Shannon | Missouri | 23 | 5,979 | 409 |
| County 09001 | 09 | 6 | 5,960 | 512 |
| Taylor | Georgia | 4 | 5,947 | 340 |
| Ferry | Washington | 32 | 5,944 | 2,147 |