Montana Water Quality
Drinking water data for all 56 counties.
Avg Water Score
48.9
State Grade
D
Counties with Data
55
of 56 total
All Montana Counties
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Frequently Asked Questions
Which county in Montana has the best water quality?
Big Horn County has the highest water quality score in Montana at 86.0/100 (Grade: A), based on EPA SDWIS data.
Which county in Montana has the most water violations?
Treasure County has among the lowest water quality scores in Montana at 0.2/100. See the individual county page for detailed violation history.
Is the tap water safe to drink in Montana?
Montana has an average water quality score of 48.9/100 based on EPA Safe Drinking Water Act compliance data. Individual county scores vary — check your specific county's page for detailed information.
What contaminants are found in Montana water supplies?
Drinking water quality varies by county and water system. The EPA Safe Drinking Water Information System (SDWIS) tracks violations for contaminants like lead, nitrates, bacteria, and disinfection byproducts. See individual county pages for specific contaminant and violation history.
Data Source
Water quality data sourced from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.
Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.