Southern California · EPA violations

Southern California water systems with recent health-based EPA violations.

Nine of the 293 public water systems FilteredWTR tracks across Southern California have at least one health-based EPA violation that began in the last three years. Together they serve about 219,139 people. Another 35 systems have health-based violations on record that are older than that.

What the categories mean

The EPA files every violation under a category. The health-based categories are the ones tied to what was in the water or how it was treated.

An MCL violation means a measured contaminant went over its maximum contaminant level, the legal limit set in the National Primary Drinking Water Regulations. A TT violation means the system missed a required treatment technique. The EPA uses treatment techniques for contaminants it regulates through a required process, such as filtering surface water or controlling pipe corrosion. An MRDL violation means a disinfectant such as chlorine went over its maximum residual level.

Most other violations fall under monitoring and reporting, such as a missed sample or a late notice to customers. Those stay on a system's record and are left off the lists below.

Each violation covers a specific compliance period. It stays in the federal record after the system fixes the problem, so a violation on this page does not by itself mean the water is unsafe today. Each system's city report lists its record with dates, and the utility's annual water quality report explains what happened and how it was handled.

Health-based violations in the last three years

Indian Hills Camp in San Diego County has the most, with 16 recent health-based violations on a system that serves 36 people. The largest system on the list is Monterey Park-City, Water Dept., serving 61,096 people, with 1 recent violation. "Recent" counts violations whose compliance period began in the three years before Oct 2026. "Latest began" is the start date of the newest health-based violation. Two systems have no FilteredWTR city report yet and show "No report" in that column.

Systems with older health-based violations only

These 35 systems have no health-based violations that began in the last three years. Each has at least one older one in the EPA record. The other 249 systems FilteredWTR tracks have no health-based violations on record.

Sources: U.S. EPA, Safe Drinking Water Information System · U.S. Environmental Protection Agency, National Primary Drinking Water Regulations. Violation records as of Oct 2026.

Related guides: Lead in Southern California tap water · Hard water in Orange County · Chlorine byproducts in Orange County · All city water reports