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Map of Drinking Water Purity in the United States

A 0–100 score for tap water quality based on violations, lead readings, and unregulated contaminants like PFAS. Higher is cleaner.

Data updated March 2026 - Source: EPA SDWIS + UCMR3/4/5

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environment

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County

Unit

index

Vintage

2026 Q1

States ranked by drinking water purity

51 states with data (2026 Q1). Top 10 highest and bottom 10 lowest.

Top 10 states by drinking water purity
RankStateValue
1North Dakota97
2Arkansas97
3Vermont97
4South Dakota96
5Hawaii96
6Iowa96
7Missouri95
8Nebraska95
9Kansas95
10Maine95
Bottom 10 states by drinking water purity
RankStateValue
51Arizona82
50New Jersey83
49Pennsylvania86
48Oklahoma86
47Florida88
46Alabama88
45Connecticut88
44Idaho88
43West Virginia89
42Alaska90

About this map

hearthmap renders drinking water purity as a choropleth map of the United States. Zoom in to see county values shaded against the rest of the country, and click any region to see its exact value with margin of error.

You can layer filters and a custom match score on top of drinking water purityto find places that match what matters to you. Combine it with school ratings, housing prices, commute times, and more.

Source: EPA SDWIS + UCMR3/4/5 · 2026 Q1

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