US Water Quality Rankings
National drinking water quality rankings based on EPA SDWIS data, updated 2026.
Worst Water Quality
The 10 lowest-scoring public water systems in the United States.
Best Water Quality
The 10 highest-scoring public water systems in the United States.
States by Average Score
All 50 states ranked by average water quality score.
| Rank | State | Avg Score | Grade |
|---|---|---|---|
| #1 | Washington | 94 | A |
| #2 | North Dakota | 92 | A |
| #3 | South Dakota | 91 | A |
| #4 | Maryland | 90 | A |
| #5 | Nebraska | 90 | A |
| #6 | California | 89 | B |
| #7 | Michigan | 89 | B |
| #8 | South Carolina | 89 | B |
| #9 | Maine | 87 | B |
| #10 | Minnesota | 87 | B |
| #11 | Delaware | 86 | B |
| #12 | New Hampshire | 85 | B |
| #13 | Virginia | 85 | B |
| #14 | Wisconsin | 85 | B |
| #15 | Montana | 84 | B |
| #16 | Ohio | 84 | B |
| #17 | Wyoming | 84 | B |
| #18 | Alabama | 83 | B |
| #19 | Indiana | 83 | B |
| #20 | New York | 83 | B |
| #21 | Oregon | 83 | B |
| #22 | Tennessee | 83 | B |
| #23 | Colorado | 82 | B |
| #24 | Georgia | 82 | B |
| #25 | Vermont | 81 | B |
| #26 | Arkansas | 80 | B |
| #27 | Idaho | 80 | B |
| #28 | Hawaii | 79 | B |
| #29 | Kansas | 78 | B |
| #30 | Missouri | 78 | B |
| #31 | Connecticut | 77 | B |
| #32 | Texas | 76 | B |
| #33 | Mississippi | 75 | B |
| #34 | North Carolina | 75 | B |
| #35 | Massachusetts | 74 | C |
| #36 | Nevada | 74 | C |
| #37 | Iowa | 72 | C |
| #38 | Pennsylvania | 71 | C |
| #39 | Rhode Island | 67 | C |
| #40 | Illinois | 66 | C |
| #41 | New Jersey | 66 | C |
| #42 | Kentucky | 65 | C |
| #43 | Louisiana | 65 | C |
| #44 | Florida | 64 | C |
| #45 | Utah | 62 | C |
| #46 | New Mexico | 61 | C |
| #47 | Arizona | 55 | D |
| #48 | West Virginia | 52 | D |
| #49 | Oklahoma | 38 | F |
| #50 | Alaska | 8 | F |
Most Recent Violations
The 10 most recent drinking water violations nationwide.
| Date | System | Violation | Severity | Status |
|---|---|---|---|---|
| 2026-05-11 | Southwestern Cambria Cnty Auth | Other | Minor | Unresolved |
| 2026-05-11 | Southwestern Cambria Cnty Auth | Other | Minor | Unresolved |
| 2026-05-11 | Southwestern Cambria Cnty Auth | Other | Minor | Unresolved |
| 2026-05-11 | Cranberry Twp Wtp | Other | Minor | Resolved |
| 2026-05-11 | Cranberry Twp Wtp | Other | Minor | Resolved |
| 2026-05-11 | Cranberry Twp Wtp | Other | Minor | Resolved |
| 2026-05-11 | Cranberry Twp Wtp | Other | Minor | Resolved |
| 2026-05-04 | Lakeside Wcid 2D | Other | Minor | Resolved |
| 2026-05-04 | Lakeside Wcid 2D | Other | Minor | Resolved |
| 2026-05-04 | Altoona Water Authority | Other | Minor | Unresolved |
Most Affected Contaminants
Contaminants with the highest number of violations across all US water systems.
| Rank | Contaminant | Violations |
|---|---|---|
| #1 | Copper (90th percentile) | 172 |
| #2 | Lead (90th percentile) | 50 |
Popular City Water Comparisons
High-intent city-vs-city pages for people choosing where to live.
Frequently Asked Questions
How often are WaterQ national rankings updated in 2026?
Rankings refresh whenever new EPA SDWIS data is processed. Each update recalculates system scores, grade bands, and violation context across states.
What does a WaterQ score mean?
WaterQ scores range from 0 to 100 and summarize contaminant test results, compliance violations, and recency signals from EPA-reported data.
Where can I drill down after viewing national rankings?
Use the state, city, and system pages linked from rankings to review local water systems, contaminants, and recent violations in detail.