US Drinking Water Quality Insights
National analysis of drinking water quality across all 3,144 US counties. Data from EPA Safe Drinking Water Information System (SDWIS).
National Avg Score
50.0
Best Water State
Hawaii
Counties Analyzed
3,067
Key Findings
Drinking water quality varies significantly across the United States. Hawaii leads with an average water score of 78.6, while Oklahoma has the lowest average at 15.8. The national average water score is 50.0 across 3,067 counties with data.
Health violations are not evenly distributed — some counties report zero violations while others report dozens annually. Understanding your local water quality is the first step toward protecting your household.
State Water Score Rankings
Average water quality score by state. Higher scores indicate better water quality.
Best Water Quality States
Lowest Water Quality States
Water Grade Distribution
How counties are distributed across water quality grades (A–F).
Violation Count vs. Water Score
Each point is a US county. Counties with more violations tend to have lower water scores.
Violation Rate by State
Average health violation rate per year by state.
Highest Violation Rates
Lowest Violation Rates
Top 10 Counties by Water Score
The counties with the best water quality scores nationwide.