Of the 1,000 large US water systems we could match to EPA compliance records, 88 were in violation of the Safe Drinking Water Act in every one of the last 12 quarters (three years). Together they serve about 18.5 million people. Most of those 88 systems had only monitoring, reporting or public-notice violations, which are about paperwork and testing schedules, not contamination. Seventeen had at least one health-based violation on record.
This post lists those systems, separates health-based violations from testing and reporting problems, and explains how to read the numbers.
Where this data comes from
TapWaterSafety.org grades 1,000 US public water systems, each serving more than 50,000 people. For each one we pulled its record from EPA’s Enforcement and Compliance History Online (ECHO) database. Source: EPA ECHO compliance records, checked October 7, 2026; last 12 quarters.
Key numbers from that set:
- 431 of 1,000 systems (43.1%) had at least one quarter with a violation in the last 12 quarters.
- 569 systems had no violation in any of the 12 quarters.
- 88 systems were in violation in all 12 quarters.
- 90 systems had at least one health-based violation listed in their EPA record.
Among the 431 systems with any violation, 326 had a monitoring violation, 82 had a reporting violation, 138 had a public notice or Consumer Confidence Report (CCR) violation, and 90 had a health-based violation. Many systems had more than one type.
How to read “quarters in violation”
ECHO shows a three-year compliance history, split into 12 calendar quarters. A quarter counts as “in violation” if any violation was open during it.
That means a single unresolved problem can fill all 12 boxes. Of the 88 systems in violation for all 12 quarters, 31 had just one violation listed in their record. A late report that is never formally closed out can look the same on this chart as a long string of separate problems. So the quarter count tells you how long a system has had something unresolved. It does not tell you how serious it is. For that, look at the violation type.
Health-based vs. testing and reporting violations
EPA groups drinking water violations into four categories:
- Health-based. EPA defines these as exceeding a maximum contaminant level (MCL) or maximum residual disinfectant level (MRDL), or failing a required treatment technique (TT). This is the most serious category. Note that a treatment technique violation means a required treatment or process step was not met. It is not always a measurement of a contaminant at the tap.
- Monitoring and reporting. Failing to test on schedule or to submit results on time.
- Public notice. Failing to notify customers as required.
- Other. Such as not issuing the annual Consumer Confidence Report.
In the tables below, “Health-based” shows whether the system’s EPA record lists any MCL, MRDL or TT violation, and which kind. If a specific system matters to you, open its EPA report from its page on our site to see the details.
Systems in violation all 12 quarters, with a health-based violation
These 17 systems were in violation for every quarter and had at least one health-based violation listed. They are sorted by population.
| System | State | Population | Quarters in violation (of 12) | Health-based |
|---|---|---|---|---|
| New York City System | NY | 8,271,000 | 12 | Yes (TT) |
| Boston Water and Sewer Commission (MWRA) | MA | 675,647 | 12 | Yes (TT) |
| Portland Water Bureau | OR | 666,200 | 12 | Yes (TT) |
| Trenton Water Works | NJ | 217,000 | 12 | Yes (MCL, TT) |
| Shreveport Water System | LA | 192,378 | 12 | Yes (MCL, TT) |
| City of Jackson | MS | 189,673 | 12 | Yes (MCL, TT) |
| Pembroke Pines, City of | FL | 187,459 | 12 | Yes (MCL) |
| West Palm Beach WTP | FL | 132,000 | 12 | Yes (TT) |
| Rio Rancho Water & WW Services | NM | 107,350 | 12 | Yes (TT) |
| Cicero | IL | 83,000 | 12 | Yes (TT) |
| Somerville Water Dept. (MWRA) | MA | 81,045 | 12 | Yes (TT) |
| Waukesha Water Utility | WI | 70,718 | 12 | Yes (MCL) |
| City of Pflugerville | TX | 63,464 | 12 | Yes (MCL) |
| Medford Water Dept. (MWRA) | MA | 61,700 | 12 | Yes (TT) |
| Northeast | FL | 60,557 | 12 | Yes (MCL) |
| Westchester Joint Water Works | NY | 59,629 | 12 | Yes (TT) |
| Lauderhill, City of | FL | 55,000 | 12 | Yes (MCL) |
A few notes on what these records actually say, taken from the rule names in each EPA record:
- New York City and Portland each have one open treatment technique violation under the Long Term 2 Enhanced Surface Water Treatment Rule, which sets treatment requirements for surface water against microbial pathogens. New York City’s dates to February 2017 and Portland’s to December 2017.
- Boston, Somerville and Medford each have an open treatment technique violation under the Lead and Copper Rule. Boston and Medford are also flagged in ECHO as over the lead action level (see our list of systems over the lead action level).
- Trenton Water Works has 10 open violations in its record, the most of any system in this table, including a Stage 2 disinfection byproducts MCL violation and a Lead and Copper Rule treatment technique violation.
- Westchester Joint Water Works’ single open violation is a Surface Water Treatment Rule treatment technique violation dated June 1993.
Largest systems in violation all 12 quarters, testing and reporting only
The other 71 systems in violation for all 12 quarters had no health-based violation listed. These are the 20 largest. Florida accounts for 41 of the 88 all-12-quarter systems overall.
| System | State | Population | Quarters in violation (of 12) | Violation types |
|---|---|---|---|---|
| Pinellas County Utilities | FL | 506,353 | 12 | monitoring |
| Hialeah, City of | FL | 238,000 | 12 | monitoring |
| PCUD-Pasco County Regional PWS | FL | 214,403 | 12 | monitoring, reporting |
| HCWRC/Northwest Utilities | FL | 208,982 | 12 | monitoring |
| OCUD/Western Regional Wtr Sys (5 WPS) | FL | 206,742 | 12 | monitoring |
| Tallahassee, City of | FL | 200,480 | 12 | monitoring |
| Lakeland, City of | FL | 193,297 | 12 | monitoring |
| Fort Lauderdale, City of | FL | 185,163 | 12 | monitoring, reporting |
| North Miami Beach | FL | 180,000 | 12 | monitoring, notice/CCR |
| Hollywood, City of | FL | 147,566 | 12 | monitoring, notice/CCR |
| Clermont Public Water System | OH | 133,059 | 12 | monitoring, notice/CCR |
| Miramar (East; West) Plants | FL | 127,700 | 12 | monitoring, notice/CCR |
| Indian River County Utilities (2 WTPs) | FL | 126,893 | 12 | monitoring, reporting, notice/CCR |
| City of Odessa | TX | 123,334 | 12 | monitoring, reporting, notice/CCR |
| First U.D. of Knox County | TN | 115,531 | 12 | notice/CCR |
| Lowell Regional Water Utility | MA | 115,000 | 12 | monitoring |
| Boynton Beach PWS | FL | 112,000 | 12 | monitoring, reporting, notice/CCR |
| Mustang SUD | TX | 110,826 | 12 | monitoring, reporting, notice/CCR |
| Kingsport Water Dept | TN | 107,739 | 12 | notice/CCR |
| Canton Public Water System | OH | 107,113 | 12 | notice/CCR |
None of these systems had a health-based violation in its EPA record. A monitoring violation means required testing was missed or late. It is not a finding that the water was contaminated.
Largest systems in violation 10 or 11 quarters
Another 26 systems were in violation for 10 or 11 of the 12 quarters. These are the largest 12.
| System | State | Population | Quarters in violation (of 12) | Health-based | Other violation types |
|---|---|---|---|---|---|
| Denver Water Board | CO | 1,287,000 | 11 | No | monitoring |
| Metropolitano | PR | 1,077,332 | 11 | Yes (TT) | monitoring |
| Central Alabama Water System | AL | 585,000 | 10 | No | monitoring |
| Gilbert, Town of | AZ | 247,600 | 11 | No | monitoring, reporting |
| Port St Lucie Utilities | FL | 224,485 | 11 | No | monitoring, notice/CCR |
| Syracuse City | NY | 192,000 | 10 | Yes (TT) | monitoring, notice/CCR |
| Corona, City of | CA | 168,575 | 11 | No | monitoring |
| Joliet | IL | 160,000 | 11 | Yes (TT) | monitoring |
| Naperville | IL | 156,406 | 11 | No | monitoring |
| City of Pasadena | TX | 152,000 | 10 | No | notice/CCR |
| Rockford | IL | 147,051 | 11 | No | monitoring |
| Pasco Water Department | WA | 115,102 | 11 | No | monitoring |
Denver Water’s three listed violations are all marked as closed in its EPA record, which shows that a high quarter count can reflect problems that have since been resolved.
What this list does and does not tell you
It does tell you which large systems have had unresolved compliance issues for long stretches, and whether any of those issues were in EPA’s health-based category.
It does not tell you whether your tap water is safe today. ECHO data lags: EPA says reported violations appear in ECHO about 4 to 5 months after they occur. A system may have fixed a problem since our check. Violation counts also say nothing about contaminants that are regulated loosely or not at all, which our letter grades consider separately (see our methodology).
Also keep in mind that this covers only the 1,000 larger systems on our site. Most US water systems are much smaller and are not included.
What to do if your system is on this list
- Look up your system on our search page and open its EPA report link to see each violation, its date, and whether it is open or closed.
- Read your utility’s Consumer Confidence Report. Utilities report violations in this annual report.
- Ask your utility what the violation was and whether it has been resolved. Your state drinking water program can also confirm current status.
- If a violation is health-based, follow any notice your utility has issued. For specific concerns, our guides to disinfection byproducts and lead explain the risks and what filters can help.
For context on which systems EPA has formally labeled “serious violators,” see EPA serious violators explained. For a state-by-state view, see states ranked by drinking water violations.
Note: a utility may have resolved issues since October 7, 2026. Check the 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)