U.S. Drinking Water Quality

Health violation data for 49,358 community water systems across all 50 states. Based on EPA Safe Drinking Water Information System (SDWIS) data.

Water Systems

49,358

Population Served

330,901,233

Systems with Health Violations

18,247

Total Health Violations

205,941

State Water Quality Rankings

Ranked by percentage of community water systems with health-based violations. Lower is better.

#	State	Systems	With Violations	% Affected	Pop. Served
1	Oklahoma	882	811	92%	3,655,472
2	U.S. Virgin Islands	77	64	83.1%	82,463
3	Puerto Rico	402	324	80.6%	3,294,782
4	New Mexico	593	445	75%	1,988,682
5	American Samoa	10	7	70%	48,601
6	Vermont	379	262	69.1%	462,555
7	Alaska	406	276	68%	701,132
8	Louisiana	815	544	66.7%	5,165,961
9	District of Columbia	11	7	63.6%	670,882
10	West Virginia	427	271	63.5%	1,559,157
11	Nebraska	593	351	59.2%	1,714,088
12	Arkansas	662	377	56.9%	3,063,488
13	Kentucky	375	195	52%	5,098,882
14	South Dakota	513	261	50.9%	930,000
15	Utah	553	272	49.2%	3,728,648
16	Connecticut	505	238	47.1%	2,820,514
17	Arizona	949	435	45.8%	7,438,245
18	Nevada	230	105	45.7%	3,134,139
19	Rhode Island	93	42	45.2%	1,066,285
20	Pennsylvania	1,783	790	44.3%	11,450,803
21	Kansas	855	370	43.3%	2,869,020
22	Wisconsin	978	422	43.1%	4,261,844
23	New Hampshire	681	287	42.1%	884,031
24	Oregon	943	396	42%	3,755,319
25	Massachusetts	564	236	41.8%	9,972,169
26	California	3,068	1,274	41.5%	40,371,133
27	Idaho	773	313	40.5%	1,584,441
28	Colorado	1,109	439	39.6%	7,217,682
29	Texas	4,620	1,807	39.1%	33,092,796
30	Maryland	481	187	38.9%	5,529,391
31	Wyoming	317	123	38.8%	539,928
32	Illinois	1,785	660	37%	12,090,647
33	Northern Mariana Islands	36	13	36.1%	64,004
34	Indiana	712	253	35.5%	5,217,170
35	New York	2,242	771	34.4%	18,359,077
36	Missouri	1,688	576	34.1%	5,882,217
37	North Carolina	1,958	656	33.5%	9,664,876
38	New Jersey	623	206	33.1%	8,906,185
39	Mississippi	989	316	32%	3,195,702
40	Maine	360	115	31.9%	688,847
41	South Carolina	558	164	29.4%	4,811,314
42	Tennessee	454	131	28.9%	7,836,358
43	Ohio	1,089	308	28.3%	10,444,506
44	Florida	1,513	409	27%	22,075,019
45	Montana	818	201	24.6%	816,767
46	Michigan	1,434	337	23.5%	7,490,655
47	Delaware	207	48	23.2%	1,027,238
48	Virginia	1,050	237	22.6%	7,436,904
49	North Dakota	318	56	17.6%	743,533
50	Alabama	546	94	17.2%	6,324,050
51	Hawaii	118	16	13.6%	1,507,181
52	Washington	2,410	304	12.6%	9,610,596
53	Minnesota	998	121	12.1%	4,730,761
54	Georgia	1,722	200	11.6%	10,618,265
55	Iowa	1,078	121	11.2%	3,019,942

Most Common Contaminants

Health-based violations by contaminant type across all U.S. water systems.

Contaminant	Violations	Systems Affected
TTHM	55,690	2,746
Total Haloacetic Acids (HAA5)	22,504	1,591
Arsenic	20,964	793
Groundwater Rule	15,552	3,196
Nitrate	9,021	620
Combined Radium (-226 and -228)	8,419	398
Surface Water Treatment Rule	6,883	1,161
Interim Enhanced Surface Water Treatment Rule	6,636	718
Lead and Copper Rule	6,511	2,960
LEAD AND COPPER RULE REVISIONS	6,082	4,922
Gross Alpha, Excl. Radon and U	6,005	313
Coliform (TCR)	5,791	1,941
Revised Total Coliform Rule	5,771	2,340
Fluoride	5,412	132
Combined Uranium	4,637	193

Explore More

All Contaminants → Air Quality Rankings → All States → Superfund Sites → Toxic Chemicals →

About This Data

Water quality data is from the EPA Safe Drinking Water Information System (SDWIS). PlainEnviro's fetch requests only records EPA flags as health-based, then joins them to the active community-water-system inventory. Monitoring and reporting violations are absent from this extract. Historical records do not establish current water quality or compliance.

Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services

Compiled by PlainEnviro, Publisher