Chlorite in drinking water
63 active public water systems in 20 states had a Chlorite violation in the past three years, and 6 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 Chlorite and lists the water systems whose records include a related violation. It does not show measured levels.
Is Chlorite 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.
Enter a ZIP code, town, or street address.
What it is and where it comes from
Chlorite is a disinfection byproduct formed when chlorine dioxide is used as a primary disinfectant or for taste and odor control in water treatment. Chlorine dioxide reacts with organic matter and reduces to chlorite and chlorate. It is regulated at the point of entry to the distribution system as part of the Stage 1 Disinfectants and DBP Rule.
Health effects
Elevated chlorite in drinking water can cause hemolytic anemia by oxidizing red blood cell membranes. Infants, young children, pregnant women, and individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency are especially sensitive. Chronic low-level exposure may also affect the nervous system. Most violations reflect localized high levels at specific monitoring points.
The standard and what a violation means
EPA limit: 1.0 mg/L (1,000 ppb).
Water systems with a Chlorite 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 |
|---|---|---|---|
| Texas | 10 | 0% | 0 |
| Pennsylvania | 7 | 0% | 1 |
| Arizona | 6 | 0% | 3 |
| Kansas | 6 | 1% | 0 |
| Oklahoma | 6 | 0% | 0 |
| Colorado | 5 | 0% | 0 |
| Illinois | 5 | 0% | 1 |
| Missouri | 3 | 0% | 0 |
| Maryland | 2 | 0% | 1 |
| North Carolina | 2 | 0% | 0 |
| Rhode Island | 2 | 0% | 0 |
| Connecticut | 1 | 0% | 0 |
| Kentucky | 1 | 0% | 0 |
| Louisiana | 1 | 0% | 0 |
| Minnesota | 1 | 0% | 0 |
| New Jersey | 1 | 0% | 0 |
| Nevada | 1 | 0% | 0 |
| Ohio | 1 | 0% | 0 |
| South Carolina | 1 | 0% | 0 |
| Virginia | 1 | 0% | 0 |
Largest water systems with a Chlorite 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 |
|---|---|---|---|---|
|
Aqua PA Main System Montgomery County |
822,600 | 6 | 0 | |
|
EL Paso Water Utilities El Paso County |
747,168 | 1 | 0 | |
|
Columbia City of (sc4010001) Columbia · Richland County |
354,068 | 1 | 0 | |
|
Greeley City of Weld County |
132,310 | 2 | 0 | |
|
City of Pearland Brazoria County |
125,828 | 4 | 0 | |
|
City of Yuma Yuma · Yuma County |
103,264 | 1 | 0 | |
|
City of Edinburg Hidalgo County |
85,224 | 3 | 0 | |
|
Flagstaff City of Flagstaff · Coconino County |
79,796 | 5 | 0 | |
|
Decatur Decatur · Macon County |
76,122 | 1 | 0 | |
|
Parker Wsd Douglas County |
75,949 | 4 | 0 |
About this data
A system is counted once if any of its violations in the past three years involved Chlorite, including monitoring and reporting lapses. Rules violated and status in the systems table are for the whole system, not Chlorite 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.