Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Douglas | South Dakota | 5 | 1,617 | 524 |
| Hinsdale | Colorado | 15 | 1,604 | 427 |
| Mercer | Missouri | 2 | 1,601 | 132 |
| Eddy | North Dakota | 2 | 1,595 | 64 |
| Potter | South Dakota | 4 | 1,594 | 358 |
| Armstrong | Texas | 3 | 1,590 | 174 |
| Gilliam | Oregon | 6 | 1,588 | 276 |
| Clark | Kansas | 3 | 1,576 | 488 |
| County 10130 | 10 | 1 | 1,575 | 368 |
| Greeley | Nebraska | 5 | 1,565 | 182 |
| Divide | North Dakota | 3 | 1,562 | 153 |
| Kiowa | Kansas | 3 | 1,553 | 416 |
| Hand | South Dakota | 2 | 1,547 | 285 |
| Benson | North Dakota | 6 | 1,538 | 317 |
| Dunn | North Dakota | 7 | 1,525 | 245 |
| Briscoe | Texas | 5 | 1,522 | 1,067 |
| Rawlins | Kansas | 3 | 1,519 | 221 |
| Gosper | Nebraska | 19 | 1,517 | 443 |
| Esmeralda | Nevada | 6 | 1,508 | 322 |
| Bennett | South Dakota | 1 | 1,500 | 116 |
| Echols | Georgia | 5 | 1,486 | 323 |
| Hettinger | North Dakota | 3 | 1,481 | 107 |
| Menard | Texas | 1 | 1,471 | 15 |
| Stanton | Kansas | 2 | 1,470 | 29 |
| Boyd | Nebraska | 7 | 1,458 | 399 |
| Deuel | South Dakota | 2 | 1,458 | 30 |
| Mountrail | North Dakota | 4 | 1,436 | 376 |
| Wichita | Kansas | 1 | 1,430 | 101 |
| Comanche | Kansas | 4 | 1,425 | 211 |
| Dolores | Colorado | 6 | 1,420 | 617 |
| Sheridan | Kansas | 2 | 1,407 | 75 |
| Renville | North Dakota | 3 | 1,405 | 38 |
| Shannon | South Dakota | 2 | 1,398 | 827 |
| Adams | North Dakota | 2 | 1,388 | 48 |
| Issaquena | Mississippi | 3 | 1,382 | 1,970 |
| County 10063 | 10 | 5 | 1,370 | 1,857 |
| Foard | Texas | 3 | 1,357 | 839 |
| Towner | North Dakota | 3 | 1,335 | 242 |
| King and Queen | Virginia | 8 | 1,329 | 428 |
| Dickens | Texas | 5 | 1,327 | 327 |
| Clark | Idaho | 8 | 1,267 | 163 |
| Cheyenne | Colorado | 3 | 1,265 | 762 |
| McPherson | South Dakota | 2 | 1,247 | 47 |
| Coamo Municipio | Puerto Rico | 4 | 1,240 | 2,927 |
| Grant | North Dakota | 5 | 1,224 | 89 |
| Lane | Kansas | 2 | 1,210 | 226 |
| Faulk | South Dakota | 6 | 1,204 | 484 |
| County 02067 | 02 | 1 | 1,200 | 131 |
| McCone | Montana | 7 | 1,187 | 1,179 |
| Aguadilla Municipio | Puerto Rico | 2 | 1,180 | 226 |
| Deuel | Nebraska | 2 | 1,173 | 115 |
| Cottle | Texas | 2 | 1,165 | 423 |
| Treasure | Montana | 3 | 1,162 | 795 |
| Loving | Texas | 3 | 1,155 | 492 |
| Burke | North Dakota | 7 | 1,146 | 341 |
| Billings | North Dakota | 5 | 1,139 | 57 |
| Sanborn | South Dakota | 5 | 1,137 | 934 |
| Lyman | South Dakota | 3 | 1,123 | 177 |
| Daniels | Montana | 2 | 1,108 | 473 |
| County NN043 | Navajo Nation | 1 | 1,108 | 92 |
| Jerauld | South Dakota | 2 | 1,107 | 81 |
| Logan | North Dakota | 2 | 1,102 | 41 |
| Golden Valley | North Dakota | 3 | 1,098 | 122 |
| Judith Basin | Montana | 8 | 1,069 | 2,032 |
| Anasco Municipio | Puerto Rico | 3 | 1,051 | 1,338 |
| Hodgeman | Kansas | 3 | 1,044 | 111 |
| Dundy | Nebraska | 3 | 1,037 | 396 |
| Wallace | Kansas | 3 | 1,034 | 340 |
| Irion | Texas | 3 | 1,031 | 334 |
| Carter | Montana | 5 | 996 | 314 |
| Webster | Georgia | 2 | 993 | 172 |
| Stonewall | Texas | 3 | 956 | 244 |
| Wheeler | Oregon | 5 | 942 | 369 |
| Miner | South Dakota | 2 | 937 | 130 |
| Sterling | Texas | 2 | 930 | 80 |
| Baker | Georgia | 3 | 894 | 132 |
| Kiowa | Colorado | 4 | 889 | 1,306 |
| Greeley | Kansas | 2 | 886 | 301 |
| County 09065 | 09 | 20 | 880 | 274 |
| Haakon | South Dakota | 2 | 879 | 210 |
| Motley | Texas | 3 | 864 | 1,283 |
| Rock | Nebraska | 4 | 841 | 208 |
| Yakutat City and Borough | Alaska | 3 | 833 | 626 |
| Kidder | North Dakota | 3 | 832 | 137 |
| Terrell | Texas | 2 | 827 | 142 |
| Carolina Municipio | Puerto Rico | 2 | 825 | 39 |
| Camas | Idaho | 9 | 811 | 230 |
| Steele | North Dakota | 3 | 799 | 152 |
| Robertson | Kentucky | 1 | 775 | 160 |
| Kent | Texas | 3 | 768 | 1,193 |
| Garfield | Montana | 5 | 766 | 1,179 |
| Harding | New Mexico | 2 | 758 | 354 |
| County 06119 | 06 | 2 | 743 | 49 |
| Oliver | North Dakota | 2 | 738 | 22 |
| Powder River | Montana | 3 | 730 | 262 |
| Hartley | Texas | 3 | 730 | 191 |
| Corson | South Dakota | 3 | 727 | 453 |
| Throckmorton | Texas | 1 | 720 | 351 |
| Manu'a District | American Samoa | 3 | 719 | 719 |
| Jackson | South Dakota | 2 | 717 | 190 |