Drinking Water Safety by State

EPA's Safe Drinking Water Information System (SDWIS) catalogs every public water system violation in the U.S. Health-based violations are the ones that matter most — exceedances of MCLs (maximum contaminant levels) for substances with known health effects. The per-capita column normalizes for state size; small states with concentrated rural systems often rank high on rate without high absolute counts.

Highest violation rate Wyoming 86.41 violations per 100k pop

Lowest violation rate California 1.28 violations per 100k pop

States with health-based violations 0 out of 50 tracked

States ranked by SDWIS violations per capita

#	State	Total Violations	Per 100k Pop.	Population	Median Home
1	Wyoming	501	86.41	579,761	$464,500
2	Vermont	501	77.64	645,254	$448,400
3	Alaska	501	68.26	733,971	$427,100
4	North Dakota	501	64.28	779,361	$311,200
5	South Dakota	501	55.72	899,194	$346,600
6	Delaware	501	49.81	1,005,872	$384,500
7	Rhode Island	501	45.74	1,095,371	$536,900
8	Montana	501	45.34	1,105,072	$528,600
9	Maine	501	36.37	1,377,400	$439,200
10	New Hampshire	501	36.10	1,387,834	$537,900
11	Hawaii	501	34.66	1,445,635	$741,300
12	West Virginia	501	28.08	1,784,462	$265,200
13	Idaho	501	26.46	1,893,296	$503,400
14	Nebraska	501	25.48	1,965,926	$319,100
15	New Mexico	501	23.69	2,114,768	$395,500
16	Kansas	501	17.05	2,937,569	$316,300
17	Mississippi	501	16.97	2,951,438	$284,300
18	Arkansas	501	16.52	3,032,651	$275,500
19	Nevada	501	15.95	3,141,000	$481,200
20	Iowa	501	15.68	3,195,937	$258,700
21	Utah	501	15.04	3,331,187	$560,200
22	Connecticut	501	13.92	3,598,348	$498,000
23	Oklahoma	501	12.54	3,995,260	$264,600
24	Oregon	501	11.82	4,238,714	$525,500
25	Kentucky	501	11.11	4,510,725	$284,400
26	Louisiana	501	10.84	4,621,025	$269,000
27	Alabama	501	9.91	5,054,253	$312,600
28	South Carolina	501	9.61	5,212,774	$394,000
29	Minnesota	501	8.77	5,713,716	$372,300
30	Colorado	501	8.62	5,810,774	$617,000
31	Wisconsin	501	8.50	5,892,023	$361,600
32	Missouri	501	8.12	6,168,181	$297,500
33	Maryland	501	8.12	6,170,738	$477,300
34	Indiana	501	7.35	6,811,752	$287,300
35	Tennessee	501	7.17	6,986,082	$413,200
36	Massachusetts	501	7.16	6,992,395	$688,100
37	Arizona	501	6.89	7,268,175	$453,800
38	Washington	501	6.47	7,740,984	$651,800
39	Virginia	501	5.79	8,657,499	$499,300
40	New Jersey	501	5.41	9,267,014	$579,900
41	Michigan	501	4.98	10,051,595	$297,900
42	North Carolina	501	4.73	10,584,340	$397,600
43	Georgia	501	4.63	10,822,590	$389,000
44	Ohio	501	4.25	11,780,046	$282,600
45	Illinois	501	3.95	12,692,653	$337,900
46	Pennsylvania	501	3.86	12,986,518	$330,200
47	New York	501	2.52	19,872,319	$620,500
48	Florida	501	2.28	21,928,881	$421,500
49	Texas	501	1.69	29,640,343	$356,100
50	California	501	1.28	39,242,785	$887,400

Method

Total violations = all SDWIS-recorded violations in the state, including monitoring + reporting + treatment-technique violations.
Health-based = subset of violations involving exceedances of EPA Maximum Contaminant Levels for substances with health effects (lead, arsenic, nitrate, coliform, disinfection byproducts, etc.).
Per-capita normalization separates true exposure intensity from population scale. A state with 200 violations across 30M residents is meaningfully different from 200 violations across 800k residents.
Public systems only. SDWIS does not cover private wells. Roughly 13% of U.S. households are on private wells; testing is the homeowner's responsibility.

Sources: EPA SDWIS, U.S. Census ACS.