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State Water Quality Rankings 2026
Compare tap water quality across all 50 US states and Washington D.C. Rankings based on population-weighted scores from city-level EPA data. Discover which states and cities have the cleanest tap water, plus rankings for major US cities.
Key Findings
What State Has the Cleanest Tap Water?
Hawaii ranks #1 for the cleanest tap water in the US with a grade of A and a score of 97.5 out of 100, based on population-weighted EPA data.
All States Ranked
Not Ranked
We do not hold enough water-quality test results to rank these states against the others. Each one is ranked once enough of its cities have test results on file.
- District of ColumbiaNot enough test data to rankBased on 1 scored city covering 4.4% of the state's served population.
- South DakotaNot enough test data to rankBased on 2 scored cities covering 3.1% of the state's served population.
Which Cities Have the Cleanest Tap Water in the US?
Of the 301 cities of 100,000+ people in our data, 5 carry the Safe label; they are listed by size, not ranked.
Water Quality in Major US Cities
Cities of 100,000 or more people (Census estimate), listed by size, not ranked.
Major Cities Carrying the Safe Label
Major Cities Carrying the Danger Label
States and Cities With the Worst Water Quality
These states and cities have the most room for improvement in water quality.
Bottom 10 States
Cities Carrying the Danger Label
Of the 301 cities of 100,000+ people in our data, 3 carry the Danger label; they are listed by size, not ranked.
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Frequently Asked Questions About US Water Quality Rankings
Hawaii has the cleanest tap water in the US, ranking #1 with a grade of A and a score of 97.5 out of 100. The top 5 states for water quality are Hawaii, Oregon, New Mexico, Arkansas, Vermont.
Methodology
State rankings are calculated using population-weighted average water quality scores from city-level data. Each city's score (0-100) is based on contaminant levels relative to EPA guidelines, with higher scores indicating better water quality; a city with no water-quality test results on file is not scored. Grades are assigned as: A (80+), B (60-79), C (40-59), D (20-39), F (<20). A state is ranked only when at least 10 of its cities are scored and those cities cover at least 5% of the state's served population. States below that floor, including states with no scored city at all, are listed as not ranked, with no rank, grade or score, until enough of their cities have test results on file — see each state's scored-city count and population coverage. Cities whose water systems report no served population are excluded from the weighted average (87 of 12,749 nationally), because a zero weight cannot contribute to a population-weighted mean.
Data Sources
- EPA Safe Drinking Water Information System (SDWIS) violation data
- Annual Consumer Confidence Reports from water utilities
- State environmental agency databases
- City-level water quality testing results for 9,500+ cities
Scoring Criteria
Each state's score is calculated as a population-weighted average of city scores. City scores (0-100) are based on:
- Number of contaminants exceeding EPA Maximum Contaminant Levels (MCLs)
- Number of contaminants exceeding EPA's health goal (MCLG, or MRDLG for a disinfectant), or its legal limit (MCL) where EPA sets no health goal
- Severity and frequency of violations
- Overall water system compliance history
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