Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Osage | Missouri | 13 | 8,202 | 905 |
| Lancaster | Virginia | 38 | 8,199 | 1,419 |
| Price | Wisconsin | 75 | 8,198 | 1,842 |
| Moore | Tennessee | 2 | 8,184 | 100 |
| Tillman | Oklahoma | 7 | 8,179 | 4,413 |
| Greenlee | Arizona | 11 | 8,173 | 2,184 |
| Pocahontas | West Virginia | 40 | 8,167 | 7,989 |
| Blaine | Oklahoma | 15 | 8,155 | 3,283 |
| Rice | Kansas | 8 | 8,153 | 594 |
| Stevens | Minnesota | 21 | 8,136 | 249 |
| La Salle | Texas | 7 | 8,118 | 748 |
| Tripp | South Dakota | 3 | 8,104 | 262 |
| Ellsworth | Kansas | 7 | 8,084 | 751 |
| Presidio | Texas | 7 | 8,079 | 3,454 |
| Glades | Florida | 15 | 8,077 | 1,076 |
| East Carroll Parish | Louisiana | 4 | 8,070 | 675 |
| Cheyenne | Nebraska | 9 | 8,051 | 540 |
| Johnson | Illinois | 7 | 8,047 | 587 |
| Forest | Wisconsin | 57 | 8,038 | 1,162 |
| Calhoun | Iowa | 14 | 8,014 | 949 |
| Cuming | Nebraska | 8 | 8,009 | 460 |
| Trimble | Kentucky | 2 | 8,007 | 76 |
| Granite | Montana | 21 | 7,984 | 2,193 |
| Marshall | Kansas | 11 | 7,965 | 636 |
| Marshall | Minnesota | 17 | 7,959 | 264 |
| Blackford | Indiana | 8 | 7,938 | 526 |
| Pulaski | Georgia | 2 | 7,937 | 84 |
| Pembina | North Dakota | 8 | 7,930 | 317 |
| Emmet | Iowa | 11 | 7,892 | 477 |
| Bear Lake | Idaho | 33 | 7,887 | 1,296 |
| Clarke | Virginia | 21 | 7,887 | 784 |
| Chickasaw | Iowa | 21 | 7,872 | 2,217 |
| Washakie | Wyoming | 13 | 7,872 | 255 |
| Charlton | Georgia | 8 | 7,869 | 275 |
| Hamilton | Illinois | 4 | 7,864 | 127 |
| Fulton | Kentucky | 2 | 7,853 | 426 |
| Gallatin | Kentucky | 2 | 7,848 | 363 |
| Schoolcraft | Michigan | 67 | 7,836 | 1,156 |
| Kiowa | Oklahoma | 10 | 7,821 | 2,173 |
| Pershing | Nevada | 15 | 7,816 | 1,969 |
| Gasconade | Missouri | 17 | 7,808 | 1,416 |
| Early | Georgia | 12 | 7,806 | 229 |
| Richardson | Nebraska | 11 | 7,804 | 678 |
| Shelby | Iowa | 8 | 7,802 | 459 |
| Mitchell | Kansas | 9 | 7,799 | 1,688 |
| Lake | Michigan | 76 | 7,773 | 2,505 |
| Hancock | Iowa | 18 | 7,764 | 1,251 |
| Cedar | Nebraska | 18 | 7,756 | 1,068 |
| Kanabec | Minnesota | 36 | 7,739 | 188 |
| Pratt | Kansas | 11 | 7,731 | 871 |
| Lincoln | Colorado | 6 | 7,725 | 770 |
| Woods | Oklahoma | 10 | 7,723 | 1,070 |
| Kit Carson | Colorado | 7 | 7,697 | 3,262 |
| Guthrie | Iowa | 10 | 7,697 | 856 |
| Montmorency | Michigan | 55 | 7,678 | 1,332 |
| Yuma | Colorado | 11 | 7,667 | 4,713 |
| Rusk | Wisconsin | 86 | 7,660 | 4,000 |
| Traill | North Dakota | 5 | 7,644 | 96 |
| Wade Hampton Census Area | Alaska | 13 | 7,639 | 13,488 |
| Custer | Nebraska | 16 | 7,623 | 764 |
| Adair | Iowa | 6 | 7,600 | 414 |
| Hickory | Missouri | 45 | 7,583 | 3,253 |
| Alexander | Illinois | 6 | 7,545 | 269 |
| Guaynabo Municipio | Puerto Rico | 3 | 7,541 | 310 |
| Union | Iowa | 1 | 7,536 | 72 |
| Benton | Indiana | 8 | 7,527 | 2,008 |
| Middlesex | Virginia | 29 | 7,524 | 636 |
| Nemaha | Nebraska | 11 | 7,513 | 409 |
| Burt | Nebraska | 7 | 7,511 | 107 |
| St. Clair | Missouri | 15 | 7,490 | 1,478 |
| Childress | Texas | 8 | 7,476 | 249 |
| Teton | Idaho | 26 | 7,429 | 1,597 |
| Oscoda | Michigan | 70 | 7,420 | 452 |
| Wilkes | Georgia | 3 | 7,419 | 100 |
| Jefferson | Nebraska | 17 | 7,416 | 636 |
| Rosebud | Montana | 15 | 7,415 | 3,651 |
| Holt | Nebraska | 16 | 7,402 | 586 |
| Madison | Iowa | 3 | 7,399 | 365 |
| McCook | South Dakota | 6 | 7,366 | 668 |
| Cloud | Kansas | 7 | 7,364 | 357 |
| Dallas | Arkansas | 6 | 7,358 | 201 |
| Marion | Georgia | 3 | 7,343 | 338 |
| Boise | Idaho | 56 | 7,343 | 3,508 |
| Buckingham | Virginia | 13 | 7,322 | 492 |
| Liberty | Florida | 14 | 7,321 | 138 |
| Howard | Iowa | 21 | 7,302 | 2,026 |
| San Saba | Texas | 9 | 7,295 | 1,182 |
| Ohio | Indiana | 3 | 7,293 | 183 |
| Sweet Grass | Montana | 15 | 7,279 | 1,071 |
| Anderson | Kansas | 7 | 7,276 | 495 |
| Luce | Michigan | 52 | 7,239 | 1,181 |
| Wilkinson | Georgia | 9 | 7,237 | 334 |
| Maricao Municipio | Puerto Rico | 4 | 7,231 | 1,134 |
| Crawford | Indiana | 7 | 7,215 | 522 |
| Tyler | West Virginia | 6 | 7,202 | 2,276 |
| Appanoose | Iowa | 5 | 7,200 | 235 |
| Monroe | Arkansas | 6 | 7,173 | 692 |
| Cotton | Oklahoma | 5 | 7,167 | 1,512 |
| Pipestone | Minnesota | 12 | 7,166 | 277 |
| Las Marias Municipio | Puerto Rico | 1 | 7,166 | 206 |