Rankings Infrastructure TapWaterData.com — State Water Quality Rankings

Water Quality by State

Hawaii has the best tap water in the U.S., an A grade at 99.9. Oklahoma ranks last with a B grade at 72.6.

Entries ranked
50
States represented
50
Water Quality Score
99.9

Key takeaways

Water Quality by State

Hawaii has the best water quality of any

99.9

Hawaii

Hawaii has the best water quality of any state, an A grade with a score of 99.9 out of 100, based on testing across 30 cities.

North Carolina ranks second at

99.7

North Carolina

North Carolina ranks second at 99.7 across 260 cities tested, the widest testing coverage among the top three. New Hampshire follows in third at 99.5 from 37 cities.

Oklahoma has the lowest score in the ranking,

72.6

Oklahoma

Oklahoma has the lowest score in the ranking, a B grade at 72.6, more than 27 points below Hawaii's leading score.

Map

Water Quality by State Map

Water Quality Score
No data
Hawaii and North Carolina carry the darkest shading with scores of 99.9 and 99.7. Oklahoma is the lightest, with the lowest score at 72.6.
Water Quality by State Map
Rank State Water Quality Score
1 Hawaii 99.9
2 North Carolina 99.7
3 New Hampshire 99.5
4 Louisiana 98.9
5 Alaska 97.7
6 South Dakota 96.5
7 New Mexico 95.9
8 Indiana 95.2
9 Oregon 90.5
10 Vermont 88.2
11 Tennessee 87.6
12 Massachusetts 87.3
13 Colorado 86.7
14 Rhode Island 85.8
15 Maine 85.6
16 Washington 85.6
17 Maryland 85.4
18 Georgia 84.8
19 Mississippi 84.6
20 Wyoming 84.3
21 Alabama 84.1
22 North Dakota 84
23 Arkansas 83.7
24 California 83.7
25 South Carolina 83.4
26 Michigan 83.1
27 New York 83.1
28 Virginia 83
29 Montana 82.4
30 West Virginia 82.3
31 Iowa 81.7
32 Idaho 81.7
33 Delaware 81.3
34 Nebraska 81.3
35 Ohio 81
36 Florida 80.6
37 Kentucky 80.5
38 Connecticut 80.1
39 New Jersey 79.8
40 Minnesota 78.8
41 Texas 78.1
42 Wisconsin 77.7
43 Arizona 77.4
44 Utah 77.3
45 Illinois 76.8
46 Missouri 76.2
47 Kansas 76.1
48 Nevada 76.1
49 Pennsylvania 75.9
50 Oklahoma 72.6

Hawaii and North Carolina carry the darkest shading with scores of 99.9 and 99.7. Oklahoma is the lightest, with the lowest score at 72.6.

Score: highest, median, and lowest

Median

83

Across 50 ranked states

The highest value is 1.4× the lowest.

Water Quality by State Table

50 entries
Grade

Distribution

How score varies across 50 states

50 states

The top three states account for 7.1% of the combined total.

States With the Best and Worst Tap Water

Top 10 Highest — Score

Hawaii flag Hawaii 99.9
North Carolina flag North Carolina 99.7
New Hampshire flag New Hampshire 99.5
Louisiana flag Louisiana 98.9
Alaska flag Alaska 97.7
South Dakota flag South Dakota 96.5
New Mexico flag New Mexico 95.9
Indiana flag Indiana 95.2
Oregon flag Oregon 90.5
Vermont flag Vermont 88.2

Top 10 Lowest — Score

Oklahoma flag Oklahoma 72.6
Pennsylvania flag Pennsylvania 75.9
Nevada flag Nevada 76.1
Kansas flag Kansas 76.1
Missouri flag Missouri 76.2
Illinois flag Illinois 76.8
Utah flag Utah 77.3
Arizona flag Arizona 77.4
Wisconsin flag Wisconsin 77.7
Texas flag Texas 78.1

States With the Best Water Quality

Clear glass of drinking water held up against natural light
Hawaii leads every state with a water quality score of 99.9 out of 100, drawn from tests across 30 cities.

Hawaii leads every state with a score of 99.9 out of 100, drawn from tests across 30 cities. North Carolina follows at 99.7 despite testing 260 cities, and New Hampshire rounds out the top three at 99.5 from just 37 cities.

Louisiana holds fourth at 98.9, and Alaska rounds out the top five at 97.7 from only 13 cities tested, the smallest sample among the leaders. All ten states in this group carry an A grade.

Rank
1
State
Hawaii
Grade
A
Score
99.9
Cities Tested
30
Rank
2
State
North Carolina
Grade
A
Score
99.7
Cities Tested
260
Rank
3
State
New Hampshire
Grade
A
Score
99.5
Cities Tested
37
Rank
4
State
Louisiana
Grade
A
Score
98.9
Cities Tested
141
Rank
5
State
Alaska
Grade
A
Score
97.7
Cities Tested
13
Rank
6
State
South Dakota
Grade
A
Score
96.5
Cities Tested
38
Rank
7
State
New Mexico
Grade
A
Score
95.9
Cities Tested
69
Rank
8
State
Indiana
Grade
A
Score
95.2
Cities Tested
164
Rank
9
State
Oregon
Grade
A
Score
90.5
Cities Tested
110
Rank
10
State
Vermont
Grade
A
Score
88.2
Cities Tested
26

States With the Worst Water Quality

Water treatment facility with tanks and piping
Oklahoma ranks last in the water quality ranking at 72.6, more than 27 points below Hawaii's leading score of 99.9.

Oklahoma ranks last at 72.6, more than 27 points below Hawaii's leading 99.9. Pennsylvania sits second-worst at 75.9 despite testing 589 cities, the second-highest total in the country.

Kansas and Nevada tie at 76.1, and both carry a B grade. Every state ranked 41st through 50th shares the same B grade, the lowest tier in this ranking.

Rank
41
State
Texas
Grade
B
Score
78.1
Cities Tested
647
Rank
42
State
Wisconsin
Grade
B
Score
77.7
Cities Tested
173
Rank
43
State
Arizona
Grade
B
Score
77.4
Cities Tested
87
Rank
44
State
Utah
Grade
B
Score
77.3
Cities Tested
90
Rank
45
State
Illinois
Grade
B
Score
76.8
Cities Tested
315
Rank
46
State
Missouri
Grade
B
Score
76.2
Cities Tested
186
Rank
47
State
Kansas
Grade
B
Score
76.1
Cities Tested
125
Rank
48
State
Nevada
Grade
B
Score
76.1
Cities Tested
27
Rank
49
State
Pennsylvania
Grade
B
Score
75.9
Cities Tested
589
Rank
50
State
Oklahoma
Grade
B
Score
72.6
Cities Tested
154

Most Cities Tested for Water Quality

California tested 765 cities for water quality, more than any other state, yet its score of 83.7 lands only 24th nationally. Texas ranks second in testing volume at 647 cities with a score of 78.1, and Pennsylvania follows at 589 cities with a 75.9.

North Carolina shows the opposite pattern. Its 260 cities tested rank tenth nationally, yet its score of 99.7 sits second overall, trailing only Hawaii's 99.9.

Rank
1
State
California
Cities Tested
765
Score
83.7
Rank
2
State
Texas
Cities Tested
647
Score
78.1
Rank
3
State
Pennsylvania
Cities Tested
589
Score
75.9
Rank
4
State
New Jersey
Cities Tested
402
Score
79.8
Rank
5
State
Florida
Cities Tested
386
Score
80.6
Rank
6
State
New York
Cities Tested
357
Score
83.1
Rank
7
State
Illinois
Cities Tested
315
Score
76.8
Rank
8
State
Ohio
Cities Tested
266
Score
81.0
Rank
9
State
Washington
Cities Tested
262
Score
85.6
Rank
10
State
North Carolina
Cities Tested
260
Score
99.7

Quick Answers

Which state has the best water quality?
Hawaii has the best water quality of any state, an A grade with a score of 99.9 out of 100, based on testing across 30 cities.
Which state has the worst water quality?
Oklahoma has the lowest score in the ranking, a B grade at 72.6, more than 27 points below Hawaii's leading score.
How many states get an A grade for water quality?
38 states earn an A grade. Connecticut's 80.1 score is the lowest A on record, just 0.3 points above New Jersey's 79.8, the highest B.
Which state tested the most cities for water quality?
California tested 765 cities, more than any other state, though its score of 83.7 lands only 24th nationally.
Does testing more cities mean better water quality?
Texas tested 647 cities but scored 78.1, while North Carolina tested 260 cities and scored 99.7. More cities tested did not correspond to a higher score for these two states.
Which states tie for the same water quality score?
Kansas and Nevada tie at 76.1, and Iowa and Idaho tie at 81.7.

Methodology

TapWaterData.com grades state tap water on a 100-point scale. Cities Tested and Population Served come from the same dataset.

Sources

Information is cross-referenced with official state archives.
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