EPA Safe Drinking Water Data
Water Quality by County
Drinking water quality scores, violation history, and safety grades for every US county. Powered by EPA data.
3,144
Total Counties
3,067
With Water Data
A–F
Quality Grades
Allegheny County
Pennsylvania
Water Quality Grade
C
Quality Grade
C
Quality Score
62.0
Health Violations (5yr)
102
Violation Rate
5.2/yr
How We Grade Water Quality
Counties receive a letter grade based on EPA compliance history and violation data.
A
Excellent
Score: 90–100
B
Good
Score: 75–89
C
Moderate
Score: 60–74
D
Poor
Score: 40–59
F
Failing
Score: Below 40
Browse by State
Select a state to view water quality data for every county.
Alabama
67 counties
Alaska
30 counties
Arizona
15 counties
Arkansas
75 counties
California
58 counties
Colorado
64 counties
Connecticut
9 counties
Delaware
3 counties
District of Columbia
1 county
Florida
67 counties
Georgia
159 counties
Hawaii
5 counties
Idaho
44 counties
Illinois
102 counties
Indiana
92 counties
Iowa
99 counties
Kansas
105 counties
Kentucky
120 counties
Louisiana
64 counties
Maine
16 counties
Maryland
24 counties
Massachusetts
14 counties
Michigan
83 counties
Minnesota
87 counties
Mississippi
82 counties
Missouri
115 counties
Montana
56 counties
Nebraska
93 counties
Nevada
17 counties
New Hampshire
10 counties
New Jersey
21 counties
New Mexico
33 counties
New York
62 counties
North Carolina
100 counties
North Dakota
53 counties
Ohio
88 counties
Oklahoma
77 counties
Oregon
36 counties
Pennsylvania
67 counties
Rhode Island
5 counties
South Carolina
46 counties
South Dakota
66 counties
Tennessee
95 counties
Texas
254 counties
Utah
29 counties
Vermont
14 counties
Virginia
133 counties
Washington
39 counties
West Virginia
55 counties
Wisconsin
72 counties
Wyoming
23 counties
Best Water Quality Counties
Counties with the highest water quality scores.
Why Water Quality Matters
Know Your Water
Find out if your county has had health-based violations from EPA data.
Compare Counties
Compare water quality grades across counties before buying a home.
Stay Protected
If your county has violations, consider water filtration solutions.