Montana water quality by county
56 counties with public water systems. Pick a county to see every system that serves it.
| County | Active systems | People served | Share with violations, 3 yr | Serious violators | Health flags |
|---|---|---|---|---|---|
| Beaverhead County | 48 | 9,494 | 1 | 1 | |
| Big Horn County | 23 | 10,335 | 1 | 2 | |
| Blaine County | 12 | 2,672 | 0 | 2 | |
| Broadwater County | 20 | 8,977 | 1 | 0 | |
| Carbon County | 36 | 9,149 | 0 | 0 | |
| Carter County | 5 | 996 | 0 | 0 | |
| Cascade County | 97 | 96,001 | 0 | 0 | |
| Chouteau County | 12 | 3,456 | 1 | 0 | |
| Custer County | 11 | 10,579 | 0 | 0 | |
| Daniels County | 2 | 1,108 | 0 | 0 | |
| Dawson County | 32 | 10,547 | 0 | 1 | |
| Deer Lodge County | 16 | 9,588 | 0 | 0 | |
| Fallon County | 4 | 2,185 | 0 | 0 | |
| Fergus County | 21 | 11,187 | 0 | 2 | |
| Flathead County | 330 | 108,099 | 0 | 4 | |
| Gallatin County | 207 | 147,480 | 2 | 6 | |
| Garfield County | 5 | 766 | 0 | 0 | |
| Glacier County | 27 | 11,053 | 0 | 0 | |
| Golden Valley County | 4 | 514 | 0 | 0 | |
| Granite County | 21 | 7,984 | 0 | 1 | |
| Hill County | 17 | 15,050 | 0 | 0 | |
| Jefferson County | 42 | 10,189 | 0 | 1 | |
| Judith Basin County | 8 | 1,069 | 0 | 0 | |
| Lake County | 88 | 19,562 | 0 | 1 | |
| Lewis and Clark County | 164 | 67,965 | 4 | 6 | |
| Liberty County | 8 | 1,827 | 0 | 1 | |
| Lincoln County | 92 | 19,484 | 0 | 6 | |
| Madison County | 46 | 14,432 | 0 | 1 | |
| McCone County | 6 | 1,161 | 0 | 0 | |
| Meagher County | 8 | 1,825 | 0 | 0 | |
| Mineral County | 37 | 16,830 | 0 | 0 | |
| Missoula County | 245 | 140,358 | 0 | 5 | |
| Musselshell County | 7 | 2,795 | 0 | 0 | |
| Park County | 61 | 18,064 | 0 | 2 | |
| Petroleum County | 1 | 187 | 0 | 0 | |
| Phillips County | 12 | 2,773 | 0 | 0 | |
| Pondera County | 12 | 4,664 | 0 | 0 | |
| Powder River County | 3 | 730 | 0 | 0 | |
| Powell County | 17 | 6,181 | 0 | 1 | |
| Prairie County | 7 | 501 | 0 | 0 | |
| Ravalli County | 130 | 30,685 | 1 | 3 | |
| Richland County | 16 | 7,074 | 1 | 2 | |
| Roosevelt County | 4 | 4,519 | 0 | 0 | |
| Rosebud County | 15 | 7,415 | 0 | 0 | |
| Sanders County | 44 | 9,595 | 0 | 0 | |
| Sheridan County | 8 | 2,764 | 0 | 1 | |
| Silver Bow County | 24 | 43,130 | 0 | 0 | |
| Stillwater County | 30 | 8,352 | 0 | 0 | |
| Sweet Grass County | 16 | 7,304 | 1 | 0 | |
| Teton County | 16 | 4,960 | 0 | 0 | |
| Toole County | 18 | 6,498 | 0 | 0 | |
| Treasure County | 3 | 1,162 | 0 | 0 | |
| Valley County | 13 | 6,060 | 0 | 1 | |
| Wheatland County | 8 | 1,697 | 0 | 0 | |
| Wibaux County | 2 | 577 | 0 | 0 | |
| Yellowstone County | 118 | 170,080 | 2 | 1 |
under 30% 30 to 59% 60% and over
About this data
Share with violations counts any violation in the past three years, including monitoring and reporting lapses. Counts cover active systems; systems serving more than one county are counted in each.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The Montana records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet. Retrieved from ECHO on Oct 11, 2026.