PlainWater

50-state ranking · EPA SDWIS

Tap Water Quality by State

States ranked by the share of public water systems with at least one recorded EPA SDWIS violation. This compliance-history rate is not a measure of tap-water safety, taste, or a current household exposure.

99.5%
West Virginia rate
88.3%
All-state system rate
50
States compared

The answer

West Virginia has the highest recorded SDWIS system violation rate in this 50-state comparison: 99.5% (770 of 774 systems). The rate shows historic compliance records, not whether tap water is safe today.

99.5%
West Virginia system violation rate
94.0%
Median state rate
88.3%
All-state system rate
141,122
Public water systems compared

Highest recorded system violation rates

Share of public water systems with at least one EPA SDWIS violation

rate

What this shows West Virginia leads this 50-state comparison at 99.5%. The all-state system rate is 88.3%; use the linked state profile for its full compliance context.

Source EPA Safe Drinking Water Information System (SDWIS) As of 2026-05-15

All 50 states, ranked by recorded system violation rate

Rate = systems with at least one recorded SDWIS violation ÷ all public water systems in the state. The underlying records include different violation types and reporting histories, so this ranking is a place to investigate, not a safety verdict.

# State Systems With ≥1 violation Recorded rate
1 West Virginia 774 770 99.5%
2 Kansas 957 948 99.1%
3 Kentucky 424 420 99.1%
4 Alabama 562 554 98.6%
5 Oregon 2,518 2,481 98.5%
6 Arizona 1,493 1,469 98.4%
7 Oklahoma 1,262 1,239 98.2%
8 Alaska 1,326 1,298 97.9%
9 Utah 1,068 1,042 97.6%
10 Pennsylvania 7,701 7,480 97.1%
11 New Mexico 1,037 1,005 96.9%
12 Mississippi 1,185 1,139 96.1%
13 Idaho 2,005 1,927 96.1%
14 Rhode Island 463 444 95.9%
15 Indiana 3,967 3,799 95.8%
16 Missouri 2,823 2,692 95.4%
17 Massachusetts 1,599 1,522 95.2%
18 Iowa 1,795 1,708 95.2%
19 New Jersey 3,428 3,256 95.0%
20 Montana 2,263 2,144 94.7%
21 Wyoming 766 724 94.5%
22 Arkansas 1,016 960 94.5%
23 New York 8,098 7,648 94.4%
24 Connecticut 2,332 2,193 94.0%
25 North Dakota 368 346 94.0%
26 Tennessee 762 716 94.0%
27 Maine 1,864 1,744 93.6%
28 Florida 5,093 4,749 93.2%
29 Vermont 1,357 1,262 93.0%
30 North Carolina 5,020 4,663 92.9%
31 Colorado 2,193 2,030 92.6%
32 Louisiana 1,234 1,142 92.5%
33 Nevada 589 545 92.5%
34 Washington 4,557 4,199 92.1%
35 Georgia 2,382 2,194 92.1%
36 South Dakota 654 599 91.6%
37 Ohio 4,181 3,781 90.4%
38 Texas 7,351 6,631 90.2%
39 New Hampshire 2,453 2,212 90.2%
40 Virginia 2,821 2,540 90.0%
41 California 7,249 6,464 89.2%
42 Nebraska 1,309 1,164 88.9%
43 Michigan 10,959 9,440 86.1%
44 Illinois 5,117 4,134 80.8%
45 Hawaii 137 110 80.3%
46 Maryland 3,215 2,569 79.9%
47 Delaware 460 344 74.8%
48 Wisconsin 10,988 7,923 72.1%
49 South Carolina 1,390 908 65.3%
50 Minnesota 6,557 3,386 51.6%

Explore related rankings

Download the SDWIS/UCMR5 state landscape snapshot cited on this page: sdwis-state-landscape.csv (same CSV as /statistics, CC0).

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This ranking calculates each state’s share of public water systems with at least one recorded EPA SDWIS violation; no score is editorially assigned. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15.