Montana drinking water quality
Montana has 2,353 active public water systems serving 1.2 million people. 1,267 of them, 54%, had at least one EPA violation in the past three years, 228 have an unresolved violation today, and 18 are designated serious violators by the EPA.
Active systems
2,353
in 56 counties
People served
1.2M
851 community systems serve 827K
Violations, past 3 years
1,267
54% of active systems
Serious violators
18
61 systems carry a health flag
Largest counties
All 56 counties| County | People served | Systems | With violations |
|---|---|---|---|
| Yellowstone | 170,080 | 118 | 75 |
| Gallatin | 147,480 | 207 | 102 |
| Missoula | 140,358 | 245 | 90 |
| Flathead | 108,099 | 330 | 126 |
| Cascade | 96,001 | 97 | 63 |
| Lewis and Clark | 67,965 | 164 | 105 |
| Silver Bow | 43,130 | 24 | 12 |
| Ravalli | 30,685 | 130 | 53 |
| Lake | 19,562 | 88 | 42 |
| Lincoln | 19,484 | 92 | 54 |
Largest community water systems
All 2,353 systems| System | Serves | Status |
|---|---|---|
| Billings City of Yellowstone County |
114,000 | |
| Missoula Water Missoula County |
68,200 | |
| Great Falls City of Cascade County |
60,000 | |
| Bozeman City of Gallatin County |
56,000 | |
| Butte Silverbow Water Dept Silver Bow County |
33,000 | |
| Helena Water System Lewis and Clark County |
32,091 | |
| Kalispell Public Works Flathead County |
25,000 | |
| Billings Heights CO Water Dist of Yellowstone County |
12,000 | |
| Belgrade City of Gallatin County |
10,460 | |
| Whitefish City of Flathead County |
10,418 |
About the Montana data
Retrieved from EPA ECHO on Oct 11, 2026.