EPA SDWIS ~155K water systems EPA + UCMR5

Chlorine dioxide

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: 1008

Total Violations

1,629

Systems Affected

136

Health-Based %

27.5%

Most Affected State

What this means

Chlorine dioxide appears in EPA SDWIS with 1,629 recorded violations across 136 public water systems. Of those, 27.5% 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

Chlorine dioxide violations broken down by EPA classification.

Health-based (27.5%) Monitoring/Reporting (72.5%)

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
Perry Water & Light Dept	OK	221	5,230
City of Yuma	AZ	88	103,264
City of Yuma	AZ	67	103,264
Frederick Living	PA	56	640
Marworth Rehab Center	PA	52	178
Excela Westmoreland Hospital	PA	39	1,500
Chatham Co-North	NC	38	23,088
Franklin Water Supply	LA	35	8,325
Climax Molybdenum Co Henderson Mill	CO	34	165
Colorado City MD	CO	33	2,755
M & M WSC	TX	32	3,208
Jbsa - Sam Houston	TX	32	37,563
Magnolia Waterworks	AR	31	11,657
Pueblo West MD	CO	30	30,000
Oak Grove Water System	LA	30	2,955
Parish Utilities of Ascension	LA	27	9,732
Breckenridge PWS	MO	23	333
Todd Creek Village MD	CO	18	7,202
Montezuma WC	CO	18	13,797
Breckenridge PWS	MO	18	333
Lacygne, City Of	KS	16	1,119
Stroud Utilities Authority	OK	16	2,811
Rifle City Of	CO	15	9,489
Pagosa Area WSD	CO	14	11,069
Atoka Co. RWS & Swmd #4	OK	14	3,000
Creek Co RWD # 7	OK	14	2,100
Geisinger Medical Center	PA	14	6,442
Apache Junction Water District	AZ	12	15,610
Lacygne, City Of	KS	12	1,119
Antlers PWA	OK	12	2,547

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 Chlorine dioxide in drinking water? ▼

Chlorine dioxide is a contaminant tracked by the EPA under the Safe Drinking Water Act. It has caused 1,629 violations across 136 public water systems nationwide. 27.5% of these violations are health-based, meaning the contaminant exceeded Maximum Contaminant Levels (MCLs) or treatment technique requirements.

How many water systems have Chlorine dioxide violations? ▼

136 public water systems across the United States have at least one Chlorine dioxide violation recorded in the EPA SDWIS database.

Are Chlorine dioxide violations dangerous? ▼

27.5% of Chlorine dioxide 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 Chlorine dioxide 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.