Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Ward | Texas | 10 | 13,540 | 736 |
| Adjuntas Municipio | Puerto Rico | 17 | 13,537 | 4,743 |
| Pawnee | Oklahoma | 14 | 13,527 | 6,596 |
| Halifax | Virginia | 24 | 13,522 | 826 |
| Hardin | Iowa | 20 | 13,505 | 1,227 |
| Union | Illinois | 14 | 13,502 | 570 |
| Grainger | Tennessee | 10 | 13,502 | 214 |
| Monroe | Kentucky | 3 | 13,497 | 526 |
| Van Buren | Arkansas | 5 | 13,483 | 225 |
| Cass | Illinois | 12 | 13,463 | 663 |
| Iron | Michigan | 29 | 13,443 | 922 |
| Sawyer | Wisconsin | 192 | 13,437 | 3,789 |
| Jayuya Municipio | Puerto Rico | 12 | 13,426 | 7,612 |
| Bullock | Alabama | 3 | 13,413 | 117 |
| Cleveland | Arkansas | 6 | 13,354 | 115 |
| San German Municipio | Puerto Rico | 9 | 13,353 | 2,985 |
| Grady | Georgia | 20 | 13,348 | 1,859 |
| Clayton | Iowa | 45 | 13,347 | 4,028 |
| Desha | Arkansas | 11 | 13,337 | 1,048 |
| Daviess | Missouri | 11 | 13,332 | 566 |
| Adair | Oklahoma | 10 | 13,323 | 1,845 |
| Ciales Municipio | Puerto Rico | 5 | 13,316 | 1,406 |
| Jay | Indiana | 33 | 13,272 | 3,587 |
| Iowa | Iowa | 15 | 13,265 | 1,017 |
| Wayne | Tennessee | 12 | 13,241 | 1,107 |
| Newton | Indiana | 41 | 13,236 | 4,483 |
| Lyon | Kentucky | 6 | 13,230 | 481 |
| Warren | Illinois | 16 | 13,214 | 1,488 |
| Washington | Kentucky | 1 | 13,205 | 58 |
| Osceola | Iowa | 7 | 13,202 | 151 |
| Burnett | Wisconsin | 192 | 13,177 | 1,777 |
| Franklin | Indiana | 10 | 13,174 | 1,455 |
| Cherokee | Iowa | 12 | 13,151 | 388 |
| Greene | Illinois | 10 | 13,149 | 636 |
| Wetzel | West Virginia | 6 | 13,141 | 2,098 |
| Starke | Indiana | 47 | 13,102 | 4,989 |
| Lamar | Georgia | 3 | 13,101 | 239 |
| Mississippi | Missouri | 6 | 13,091 | 561 |
| Southampton | Virginia | 36 | 13,086 | 3,206 |
| Lewis | Tennessee | 5 | 13,073 | 404 |
| Custer | South Dakota | 51 | 13,071 | 2,359 |
| Taylor | Florida | 22 | 13,054 | 1,005 |
| Izard | Arkansas | 9 | 13,033 | 581 |
| Webster | Mississippi | 12 | 13,030 | 5,825 |
| Buchanan | Iowa | 20 | 13,026 | 994 |
| White Pine | Nevada | 27 | 13,026 | 2,314 |
| McIntosh | Georgia | 40 | 13,015 | 1,314 |
| Miller | Missouri | 53 | 13,013 | 4,944 |
| Cooper | Missouri | 8 | 13,010 | 853 |
| Carroll | Kentucky | 4 | 12,987 | 437 |
| Stewart | Tennessee | 15 | 12,963 | 760 |
| Guanica Municipio | Puerto Rico | 2 | 12,960 | 182 |
| Tallahatchie | Mississippi | 16 | 12,959 | 6,433 |
| Polk | North Carolina | 26 | 12,956 | 1,676 |
| Jefferson | Oklahoma | 6 | 12,925 | 3,652 |
| Claiborne | Mississippi | 7 | 12,917 | 3,571 |
| Smith | Mississippi | 13 | 12,913 | 7,020 |
| Madison | Texas | 7 | 12,860 | 275 |
| Millard | Utah | 28 | 12,855 | 5,123 |
| Hughes | Oklahoma | 10 | 12,826 | 4,103 |
| Lowndes | Alabama | 6 | 12,825 | 307 |
| De Witt | Illinois | 20 | 12,816 | 1,264 |
| Wilbarger | Texas | 8 | 12,769 | 2,328 |
| Piatt | Illinois | 15 | 12,765 | 969 |
| Moultrie | Illinois | 10 | 12,762 | 207 |
| Crawford | Wisconsin | 48 | 12,750 | 1,703 |
| Madison | Georgia | 27 | 12,709 | 1,138 |
| Catahoula Parish | Louisiana | 7 | 12,708 | 485 |
| York | Nebraska | 25 | 12,695 | 1,441 |
| County 10077 | 10 | 35 | 12,671 | 5,257 |
| Seward | Nebraska | 20 | 12,669 | 1,155 |
| Park | Colorado | 77 | 12,663 | 5,246 |
| Shelby | Illinois | 13 | 12,657 | 1,078 |
| Scurry | Texas | 4 | 12,654 | 498 |
| Monroe | Ohio | 6 | 12,610 | 451 |
| Ramsey | North Dakota | 3 | 12,603 | 64 |
| Jackson | Iowa | 26 | 12,600 | 2,827 |
| Mackinac | Michigan | 119 | 12,593 | 2,718 |
| Somervell | Texas | 12 | 12,585 | 2,304 |
| Lake | Colorado | 22 | 12,547 | 2,695 |
| Duval | Texas | 9 | 12,532 | 2,097 |
| McKenzie | North Dakota | 16 | 12,466 | 549 |
| Valley | Idaho | 57 | 12,433 | 1,987 |
| Edgar | Illinois | 11 | 12,424 | 1,089 |
| Gladwin | Michigan | 88 | 12,418 | 1,523 |
| Ashland | Wisconsin | 82 | 12,416 | 1,408 |
| Red River Parish | Louisiana | 12 | 12,413 | 2,369 |
| Houston | Tennessee | 2 | 12,408 | 258 |
| Barnes | North Dakota | 9 | 12,391 | 513 |
| Harrison | Missouri | 8 | 12,387 | 511 |
| Lawrence | Mississippi | 11 | 12,367 | 3,410 |
| Paulding | Ohio | 29 | 12,361 | 1,531 |
| Benton | Tennessee | 10 | 12,357 | 525 |
| Letcher | Kentucky | 4 | 12,355 | 1,311 |
| Lincoln | West Virginia | 8 | 12,334 | 2,719 |
| Floyd | Iowa | 18 | 12,330 | 1,063 |
| Prairie | Arkansas | 7 | 12,313 | 337 |
| Crawford | Missouri | 37 | 12,306 | 2,803 |
| Kemper | Mississippi | 12 | 12,295 | 3,391 |
| Tunica | Mississippi | 3 | 12,248 | 2,371 |