Among the large water systems we track, Arizona and Florida have the highest share with recent EPA drinking water violations: 90% of the Arizona systems and 84% of the Florida systems had at least one violation in the last three years. California, Virginia and Minnesota had the lowest shares among states with at least 10 systems. Nationally, 431 of the 1,000 systems we checked (43%) had at least one violation, but only 90 (9%) had a health-based violation listed in their record.
Before reading the rankings, one caveat matters more than any number here.
Read this first: what this ranking covers
TapWaterSafety.org grades 1,000 public water systems, each serving more than 50,000 people. That is a small slice of the country’s public water systems. Most US systems are much smaller, and none of them are in this data. So these figures describe the larger systems in each state that are on our site, not every system in the state.
Some states have only one to nine systems in our data. Percentages based on so few systems swing a lot with a single utility, so we rank only the 29 states with at least 10 systems and list the rest separately.
Source: EPA ECHO compliance records, checked October 7, 2026; last 12 quarters.
How we measured it
For each state we calculated:
- Any violation: the share of systems with at least one quarter in violation of the Safe Drinking Water Act in the last 12 quarters. This includes monitoring, reporting and public notice violations.
- Population-weighted: the share of people served by those systems. This shows how many residents are affected, not just how many utilities. One very large system can move this number a lot.
- Health-based: the share of systems whose EPA record lists at least one health-based violation. EPA defines these as exceeding a maximum contaminant level (MCL) or maximum residual disinfectant level (MRDL), or failing a required treatment technique (TT).
- Serious violators: the number of systems carrying EPA’s “serious violator” label (see what that label means).
A violation is not the same as contaminated water. Most violations in this data are about missed or late testing and reporting. For example, 58 of the 63 violation entries for Arizona systems are monitoring or reporting violations.
National picture
| Measure | Systems | Share of systems | Share of people served |
|---|---|---|---|
| At least one violation (last 12 quarters) | 431 of 1,000 | 43% | 43% |
| Health-based violation listed | 90 of 1,000 | 9% | 14% |
| EPA serious violator | 34 of 1,000 | 3% | n/a |
| In violation all 12 quarters | 88 of 1,000 | 9% | n/a |
The health-based figures count a system if its EPA record lists any MCL, MRDL or treatment technique violation.
States ranked: share of large systems with any violation
States with at least 10 systems in our data, ranked by share of systems with any violation in the last 12 quarters. Click a state to see every graded system there.
| Rank | State | Systems | Any violation | Population-weighted | Health-based | Health-based, population-weighted | Serious violators |
|---|---|---|---|---|---|---|---|
| 1 | Arizona | 21 | 19 (90%) | 96% | 3 (14%) | 5% | 0 |
| 2 | Florida | 93 | 78 (84%) | 82% | 5 (5%) | 6% | 27 |
| 3 | Missouri | 12 | 9 (75%) | 56% | 0 (0%) | 0% | 0 |
| 4 | Pennsylvania | 30 | 22 (73%) | 79% | 5 (17%) | 19% | 1 |
| 5 | Ohio | 25 | 18 (72%) | 55% | 2 (8%) | 6% | 0 |
| 6 | Illinois | 28 | 20 (71%) | 83% | 3 (11%) | 6% | 0 |
| 7 | Connecticut | 10 | 7 (70%) | 65% | 0 (0%) | 0% | 0 |
| 8 | New Jersey | 25 | 16 (64%) | 55% | 2 (8%) | 7% | 1 |
| 9 | Alabama | 16 | 10 (62%) | 66% | 2 (12%) | 18% | 0 |
| 10 | Colorado | 24 | 14 (58%) | 63% | 1 (4%) | 1% | 0 |
| 11 | Texas | 76 | 43 (57%) | 51% | 12 (16%) | 24% | 0 |
| 12 | North Carolina | 29 | 16 (55%) | 39% | 5 (17%) | 13% | 0 |
| 13 | New York | 29 | 15 (52%) | 78% | 8 (28%) | 72% | 1 |
| 14 | Oregon | 14 | 7 (50%) | 64% | 1 (7%) | 33% | 0 |
| 15 | Massachusetts | 30 | 14 (47%) | 29% | 3 (10%) | 14% | 0 |
| 16 | Maryland | 11 | 5 (45%) | 42% | 1 (9%) | 35% | 0 |
| 17 | Wisconsin | 11 | 5 (45%) | 36% | 2 (18%) | 21% | 0 |
| 18 | Indiana | 16 | 7 (44%) | 31% | 3 (19%) | 10% | 0 |
| 19 | Utah | 19 | 8 (42%) | 33% | 1 (5%) | 3% | 0 |
| 20 | Tennessee | 30 | 10 (33%) | 36% | 2 (7%) | 4% | 1 |
| 21 | Michigan | 29 | 9 (31%) | 23% | 4 (14%) | 8% | 0 |
| 22 | Washington | 36 | 10 (28%) | 19% | 0 (0%) | 0% | 0 |
| 23 | Louisiana | 15 | 4 (27%) | 27% | 4 (27%) | 27% | 2 |
| 24 | Georgia | 30 | 7 (23%) | 29% | 1 (3%) | 2% | 0 |
| 25 | South Carolina | 14 | 3 (21%) | 38% | 2 (14%) | 21% | 0 |
| 26 | Iowa | 11 | 2 (18%) | 13% | 0 (0%) | 0% | 0 |
| 27 | Minnesota | 18 | 3 (17%) | 26% | 0 (0%) | 0% | 0 |
| 28 | Virginia | 25 | 3 (12%) | 12% | 0 (0%) | 0% | 0 |
| 29 | California | 176 | 17 (10%) | 9% | 9 (5%) | 5% | 0 |
What stands out
Arizona and Florida lead on any violation, but mostly for testing and reporting. In Arizona, 19 of 21 large systems had a violation, yet only 3 had a health-based violation listed. In Florida, 78 of 93 had a violation and 5 had a health-based violation listed. Florida also has 27 of the 34 serious violators in our entire dataset.
New York looks very different by population. Only 8 of 29 New York systems (28%) had a health-based violation listed, but they serve 72% of the people covered by New York systems in our data. That is mostly one system: the New York City System, which serves about 8.3 million people and has an open treatment technique violation under the Long Term 2 Enhanced Surface Water Treatment Rule.
Texas has the most systems with health-based violations. Twelve of 76 large Texas systems (16%) had a health-based violation listed, more than any other state by count.
Louisiana’s violations are mostly health-based. Only 4 of 15 Louisiana systems had any violation, but all 4 had a health-based violation listed, and 2 are serious violators.
California has the lowest share. Only 17 of 176 California systems (10%) had a violation in the last 12 quarters. Seven of the 17 California systems with a violation have one listed under the Lead and Copper Rule Revisions, whose requirements, including an initial service line inventory, took effect October 16, 2024.
Population weighting can flip the picture. Missouri ranks 3rd by share of systems (75%) but only 56% of people served by those systems were affected. Oregon ranks 14th by share of systems, yet a third of its population in our data is served by a system with a health-based violation: the Portland Water Bureau.
States with fewer than 10 systems in our data
These are not ranked because the samples are too small. A single utility can change the percentage by 10 to 100 points.
| State | Systems | Any violation | Health-based | Serious violators |
|---|---|---|---|---|
| Arkansas | 8 | 0 | 0 | 0 |
| Kentucky | 9 | 0 | 0 | 0 |
| Puerto Rico | 8 | 5 | 3 | 0 |
| Idaho | 8 | 3 | 0 | 0 |
| Oklahoma | 8 | 4 | 2 | 0 |
| Kansas | 7 | 2 | 0 | 0 |
| New Mexico | 5 | 4 | 3 | 0 |
| Nevada | 5 | 1 | 0 | 0 |
| Mississippi | 4 | 3 | 1 | 1 |
| Delaware | 4 | 1 | 0 | 0 |
| Hawaii | 4 | 1 | 0 | 0 |
| Montana | 4 | 0 | 0 | 0 |
| Rhode Island | 4 | 2 | 0 | 0 |
| West Virginia | 3 | 2 | 0 | 0 |
| North Dakota | 3 | 0 | 0 | 0 |
| Alaska | 2 | 1 | 0 | 0 |
| Nebraska | 2 | 1 | 0 | 0 |
| New Hampshire | 2 | 0 | 0 | 0 |
| South Dakota | 2 | 0 | 0 | 0 |
| Wyoming | 2 | 0 | 0 | 0 |
| District of Columbia | 1 | 0 | 0 | 0 |
| Guam | 1 | 0 | 0 | 0 |
| Maine | 1 | 0 | 0 | 0 |
Vermont has no system in our data.
Why state numbers can differ for reasons other than water quality
States run most drinking water enforcement. EPA says front-line enforcement responsibility rests with states, territories and the Navajo Nation, with EPA keeping enforcement authority. That means states differ in how they record violations, how quickly they mark them resolved, and when they take formal action. A high violation share can reflect strict record-keeping as much as poor performance, and a low share does not guarantee every system is problem-free.
ECHO data also lags. EPA says reported violations appear in ECHO about 4 to 5 months after they occur.
Violation records also miss a lot. They track compliance with EPA’s legal limits and rules, not contaminants that are unregulated or regulated at levels some scientists consider too high. Our letter grades take those into account separately (see our methodology and EWG vs. EPA: the gap).
What to do with this information
- Look up your own system. A state ranking tells you little about your tap. Use our search page or the states index to find your utility, its grade and its EPA record.
- Check the violation type. Health-based violations matter more for health than late paperwork.
- Read your Consumer Confidence Report and ask your utility about any open violations.
For named systems with the longest-running violations, see US water systems with the most EPA violations.
Note: utilities may have resolved issues since October 7, 2026. Check each utility’s EPA ECHO report or its latest Consumer Confidence Report for current status.
Sources
- EPA ECHO: Safe Drinking Water Act Resources and FAQs
- EPA ECHO: Detailed Facility Reports (individual system reports linked from each utility page)
- EPA: Revised Lead and Copper Rule (2021 LCRR)