Nitrate in drinking water
10,272 active public water systems in 40 states had a Nitrate violation in the past three years, and 396 have one that is still unresolved.
You are on Tapcensus, an independent guide to the EPA compliance records of every public water system in the United States. This page explains Nitrate and lists the water systems whose records include a related violation. It does not show measured levels.
Is Nitrate in the records for your water system?
Enter a ZIP code, town, or street address to see the water systems that serve your area, their status, and which rules and contaminants appear in their violations.
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What it is and where it comes from
Nitrate (NO₃) is the most common chemical contaminant in US groundwater, entering from fertilizers, septic systems, and animal waste. It is odorless and tasteless — the only way to know if it's present is to test.
Health effects
Methemoglobinemia in infants under 6 months: gut bacteria convert nitrate to nitrite, which blocks oxygen transport in blood. Pregnant women should also take precautions. Chronic adult exposure at elevated levels may increase cancer risk.
The standard and what a violation means
EPA limit: 10 mg/L as nitrogen (NO₃-N).
Water systems with a Nitrate violation, by state
Active public water systems that reported at least one related violation to EPA in the past three years. Each state links to the list of its affected systems.
| State | Systems with violations, 3 yr | Share of active systems | Unresolved |
|---|---|---|---|
| Michigan | 1,392 | 12% | 43 |
| New York | 996 | 12% | 2 |
| Florida | 938 | 18% | 1 |
| Pennsylvania | 790 | 10% | 16 |
| Illinois | 613 | 12% | 6 |
| California | 526 | 7% | 41 |
| Indiana | 462 | 12% | 21 |
| Washington | 452 | 10% | 15 |
| Texas | 428 | 6% | 52 |
| Oregon | 363 | 14% | 1 |
| New Jersey | 303 | 9% | 21 |
| North Carolina | 229 | 5% | 0 |
| Wisconsin | 226 | 2% | 9 |
| Idaho | 221 | 11% | 9 |
| Arizona | 215 | 12% | 24 |
| Alaska | 210 | 16% | 1 |
| Colorado | 209 | 9% | 32 |
| Maine | 191 | 10% | 2 |
| Iowa | 190 | 11% | 34 |
| Maryland | 173 | 5% | 14 |
| West Virginia | 165 | 21% | 4 |
| Ohio | 158 | 4% | 6 |
| Connecticut | 130 | 6% | 8 |
| Utah | 122 | 11% | 3 |
| Vermont | 122 | 9% | 8 |
| Nevada | 111 | 18% | 2 |
| Mississippi | 52 | 4% | 0 |
| Minnesota | 50 | 1% | 3 |
| Tennessee | 44 | 6% | 0 |
| Kansas | 43 | 4% | 14 |
| Massachusetts | 38 | 2% | 3 |
| Rhode Island | 32 | 7% | 0 |
| New Hampshire | 28 | 1% | 1 |
| Alabama | 15 | 3% | 0 |
| Delaware | 14 | 3% | 0 |
| New Mexico | 13 | 1% | 0 |
| South Dakota | 4 | 1% | 0 |
| District of Columbia | 2 | 14% | 0 |
| Kentucky | 1 | 0% | 0 |
| Nebraska | 1 | 0% | 0 |
Largest water systems with a Nitrate violation
The ten biggest systems, by people served, whose records include a related violation in the past three years.
| System | Serves | Status | Rules violated, 3 yr | Unresolved |
|---|---|---|---|---|
|
City of Baltimore Baltimore city County |
1,600,000 | 3 | 0 | |
|
Pinellas County Utilities Clearwater · Pinellas County |
506,353 | 4 | 0 | |
|
ST Petersburg, City of Odessa · Pinellas County |
349,979 | 4 | 0 | |
|
Gilbert, Town of Gilbert · Maricopa County |
247,600 | 9 | 1 | |
|
Chandler City of Chandler · Maricopa County |
247,328 | 4 | 0 | |
|
Port ST Lucie Utilities Port St Lucie · St. Lucie County |
224,485 | 4 | 1 | |
|
Trenton Water Works Ewing Twp, Hamilton Twp, Hopewell Twp.1106- and 2 more · Mercer County |
217,000 | 8 | 2 | |
|
Collier County Regional Wtp Naples · Collier County |
216,993 | 4 | 0 | |
|
Pcud-Pasco County Regional PWS New Port Richey · Pasco County |
214,403 | 3 | 1 | |
|
City of Stockton Stockton · San Joaquin County |
192,702 | 2 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved Nitrate, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Nitrate alone. Counts cover active systems in all 50 states and the District of Columbia.
Source: the U.S. EPA's Enforcement and Compliance History Online system (ECHO), which publishes the federal Safe Drinking Water Information System. EPA's terms and values are shown as published. The records are from EPA's data refresh of Oct 7, 2026; EPA refreshes this data quarterly, and states report to EPA with a lag of three to six months, so the newest violations may not appear yet.