EPA SDWIS ~155K water systems EPA + UCMR5

Nitrate-Nitrite

Compiled by PlainWater Editorial, Drinking Water Quality Editorial Team · May 15, 2026

EPA SDWIS quarterly extract data for this analyte. Detection counts and health-based violation counts reflect the most recent federal release.

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EPA contaminant code: 1038

Total Violations

52,447

Systems Affected

5,756

Health-Based %

35.7%

Most Affected State

What this means

Nitrate-Nitrite appears in EPA SDWIS with 52,447 recorded violations across 5,756 public water systems. Of those, 35.7% are classified as health-based, meaning the reading exceeded a federally enforceable Maximum Contaminant Level or a treatment-technique requirement rather than a monitoring or reporting lapse. Health-based violations are the subset that trigger formal corrective action and public notification, so the share is a useful signal of real-world exposure risk rather than paperwork drift. State-level concentration data is not consistently reported for this contaminant, so regional interpretation should lean on the system table below rather than state aggregates. Utilities listed below are ranked by cumulative violation count, so a higher rank reflects persistence in the record rather than a single spike; readers comparing systems should consider population served alongside violation count to gauge how many households were actually exposed.

Violation Type Split

Nitrate-Nitrite violations broken down by EPA classification.

Health-based (35.7%) Monitoring/Reporting (64.3%)

Health-based violations indicate the contaminant exceeded an EPA Maximum Contaminant Level (MCL) or treatment-technique requirement; monitoring/reporting violations are procedural.

Most Affected Water Systems

System	State	Violations	Population
Canadian Co RWD # 1	OK	747	750
Okarche	OK	727	1,110
North Blaine Water Corp	OK	550	960
Hollis	OK	545	2,264
Aline	OK	543	214
Major County RWD #1	OK	531	1,000
Okarche RWD, Inc	OK	513	250
Grandfield	OK	414	1,110
King Ranch Colony	MT	382	56
Edgar, City Of	NE	376	428
Logan Co RWD #2	OK	342	1,146
Carmen Public Works Authority	OK	332	355
Loyal	OK	331	81
Geary	OK	316	1,258
Mooreland	OK	284	1,226
Thirsty Water Corp	OK	211	81
Unl-Eastern Nebr Resrch & Extension Cntr	NE	203	200
Steele City, Village Of	NE	175	60
US Gypsum	OK	168	280
Eastside MHP	OK	164	32
Prosser, Village Of	NE	161	76
Mars Petcare US Dba the Iams Company	NE	155	240
Cleo Springs	OK	152	326
Waterhole Saloon Reedpoint	MT	149	25
Rapelje Water District	MT	142	70
Belden, Village Of	NE	141	112
Homestead Water Company	NM	140	222
Humboldt, City Of	NE	134	950
Canute	OK	133	524
Akal Travel Center	NE	122	593

Drinking Water Guides

Understanding Water Quality Data

What EPA SDWIS tracks, how violations are classified, and what MCLs mean.

PFAS in Drinking Water

What forever chemicals are, EPA testing results, and 2024 standards.

Is My Water Safe?

How to assess your local water quality and when to take precautions.

Frequently Asked Questions

What is Nitrate-Nitrite in drinking water? ▼

Nitrate-Nitrite is a contaminant tracked by the EPA under the Safe Drinking Water Act. It has caused 52,447 violations across 5,756 public water systems nationwide. 35.7% of these violations are health-based, meaning the contaminant exceeded Maximum Contaminant Levels (MCLs) or treatment technique requirements.

How many water systems have Nitrate-Nitrite violations? ▼

5,756 public water systems across the United States have at least one Nitrate-Nitrite violation recorded in the EPA SDWIS database.

Are Nitrate-Nitrite violations dangerous? ▼

35.7% of Nitrate-Nitrite violations are health-based, meaning the contaminant level exceeded safe limits set by the EPA. Health-based violations require corrective action by the water system. Not all violations indicate immediate health risk, but they signal that water quality standards were not met.

Which state has the most Nitrate-Nitrite violations? ▼

State-level breakdown data is not available for this contaminant.

Where does this contaminant data come from? ▼

All violation data comes from the EPA Safe Drinking Water Information System (SDWIS), which tracks compliance for all public water systems regulated under the Safe Drinking Water Act. SDWIS records violations including Maximum Contaminant Level (MCL) exceedances, treatment technique failures, and monitoring/reporting issues.

Data Sources

Contaminant violation data from the EPA Safe Drinking Water Information System (SDWIS). Violations are categorized as health-based (Maximum Contaminant Level exceedances, treatment technique failures) or monitoring/reporting violations.

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Data sourced from EPA SDWIS and UCMR5 PFAS monitoring data. See our methodology for details. Retrieved and formatted by PlainWater Editorial

Disclaimer: This information is provided for informational purposes only and does not constitute professional advice. Data is sourced from the EPA Safe Drinking Water Information System (SDWIS). Consult a qualified professional before making decisions based on this data.

Read our methodology - how this data is sourced, computed, and verified.

Every figure on PlainWater is rendered directly from EPA SDWIS drinking-water data, no number is typed in by an editor. This page draws directly on EPA SDWIS data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.