State Hub
California Water Quality
1,182
Utilities in database
36.4M
Residents served
102
With open violations
664
PFAS monitored
Quick Answer
California public drinking water is served by 1,182 EPA-tracked water systems, providing service to approximately 36.4 million residents through public utilities. 102 of those systems currently have open health-based violations on record in the EPA federal database. 664 systems have official PFAS monitoring records from the EPA UCMR 5 program (2023–2025). About 15% of CA residents use private wells, which fall outside federal utility compliance monitoring.
102 California water systems have open health-based violations recorded in EPA SDWIS. An open violation means a contaminant exceeded a federal limit and the violation has not been formally resolved in the federal database. Check individual utility pages for current status.
Open Health-Based Violations in California
Records sourced from EPA SDWIS. A record may be under review or resolved at the utility level but not yet updated in federal records. Water Utility Report does not determine whether water is safe to drink.
Drinking Water in California
California's drinking water comes from a complex mix of surface water (rivers, reservoirs) and groundwater. The state has some of the strictest water quality regulations in the U.S., but still faces challenges from agricultural runoff, legacy industrial contamination, and aging infrastructure in older cities. The State Water Resources Control Board maintains primacy for Safe Drinking Water Act enforcement.
Highest Risk Utilities
California systems with open health-based violations in EPA records.
Safest Large Utilities
California systems with no open health violations serving 10,000+ residents.
Utilities in California
201–225 of 1,182Bellflower - Somerset Mwc
CA1910013 · 46,300 served
City of San Jose - Nsj/alviso
CA4310019 · 45,559 served
Golden State Water Company - Simi Valley
CA5610059 · 45,128 served
Oildale Mwc
CA1510015 · 44,899 served
Hawthorne-city Water Dept.
CA1910047 · 44,718 served
City of Rohnert Park
CA4910014 · 43,821 served
Elk Grove Water District
CA3410008 · 43,813 served
City of El Centro
CA1310004 · 43,772 served
Coachella Water Authority
CA3310007 · 43,590 served
Mission Springs Wd
CA3310008 · 43,484 served
Diablo Water District
CA0710007 · 43,357 served
Gswc - Norwalk
CA1910098 · 43,176 served
City of San Bruno
CA4110023 · 42,631 served
Camp Pendleton (south)
CA3710702 · 42,219 served
Indian Wells Valley W.d.
CA1510017 · 41,580 served
Carmichael Water District
CA3410004 · 41,193 served
South Coast Water District
CA3010042 · 41,118 served
California State University Fresno
CA1010339 · 41,000 served
Soquel Creek Water District
CA4410017 · 40,809 served
Pico Rivera - City, Water Dept.
CA1910042 · 40,600 served
Lompoc-city Water Utility Div
CA4210006 · 40,473 served
San Dieguito Wd
CA3710021 · 40,405 served
City of Calexico
CA1310002 · 40,357 served
Beverly Hills-city, Water Dept.
CA1910156 · 40,121 served
City of Adelanto
CA3610001 · 39,930 served
Key Contaminant Concerns in California
These contaminants appear most frequently in California utility records or pose elevated risk in this region based on EPA data.
PFAS
Per- and polyfluoroalkyl substances (PFAS) are a class of over 12,000 synthetic chemicals characterized by strong carbon-fluorine bonds that resist degradation. The two most studied — PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid) — have been phased out of U.S. manufacturing but persist widely in the environment.
EPA limit: 4 ppt
Nitrates
Nitrate (NO₃⁻) is a nitrogen-containing compound that forms naturally through the decomposition of organic matter. At elevated concentrations — almost always caused by human activity — nitrate is converted in the digestive system to nitrite, which then reacts with hemoglobin to form methemoglobin, a form of hemoglobin that cannot carry oxygen. In the body, nitrite also reacts with amines in food to form N-nitroso compounds (nitrosamines) — known carcinogens classified by the IARC as Group 2A (probable human carcinogens). The United States applies over 23 million tons of nitrogen fertilizer annually, making agricultural runoff the dominant source of nitrate contamination in U.S. groundwater.
EPA limit: 10 mg/L
DBPs
When utilities add chlorine to water to kill pathogens, it reacts with dissolved organic matter — leaves, algae, soil — to produce disinfection byproducts (DBPs). Over 600 DBPs have been identified. The EPA regulates two groups: total trihalomethanes (TTHMs, including chloroform) and haloacetic acids (HAA5). DBP levels tend to be highest in surface water systems and in warm months when organic matter is elevated.
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Arsenic (As) occurs naturally in rock and soil, dissolving into groundwater through natural weathering processes. Inorganic arsenic — the form found in drinking water — is a known human carcinogen. The western United States has particularly arsenic-rich geological formations, but elevated levels have been found in 48 states. Arsenic is tasteless and odorless.
EPA limit: 10 ppb
City Water Reports in California
Tap water quality pages for California cities — violations, PFAS records, utility profiles, and official source links.
Independent Water Testing
Find a certified lab in California
Utility compliance records show what water systems report to the EPA. An independent test from a certified laboratory confirms what's actually in your tap water. California labs can test for PFAS, lead, nitrates, bacteria, and dozens of other contaminants.
Explore Water Quality in California
Bellflower - Somerset Mwc
Violation history, PFAS records, and official source links
City of San Jose - Nsj/alviso
Violation history, PFAS records, and official source links
Golden State Water Company - Simi Valley
Violation history, PFAS records, and official source links
PFAS monitoring records — California
664 water systems in California with EPA UCMR 5 records
Active drinking water violations
102 open health-based violations on record — view official EPA SDWIS data
Lead in California drinking water
State-specific lead data, violation utilities, and testing guidance
PFAS in California drinking water
State-specific PFAS data, MCL context, and treatment options
Certified water testing labs in California
Labs certified for PFAS (EPA 533/537.1), lead, and bacteria testing
Water treatment options
Reverse osmosis, activated carbon, and filtration guides with cost ranges
Data sources and methodology
How WaterUtilityReport.com sources and validates official EPA data
Common Questions About California Drinking Water
Does California drinking water have PFAS?
664 California water systems have EPA UCMR 5 PFAS monitoring records (2023–2025)
Which California water utilities have open violations?
102 systems have open health-based violations in EPA SDWIS — search for your utility
How do I test my water in California?
State-certified labs for PFAS (EPA 533/537.1), lead, nitrate, and bacteria testing
What treatment removes PFAS from CA tap water?
Reverse osmosis removes PFAS, lead, arsenic, and nitrates — cost, maintenance, and NSF certification explained
What do California PFAS records tell me about my water?
EPA limits, health context, and what UCMR 5 detection above MRL means for your water
How is California water quality data sourced here?
EPA SDWIS violations, UCMR 5 PFAS records, and CCR data — sources, accuracy notes, and limitations
California Water FAQs
Data sources: Utility compliance and violation data from EPA SDWIS (Safe Drinking Water Information System). PFAS monitoring records from EPA UCMR 5 (Unregulated Contaminant Monitoring Rule 5, 2023–2025). Contaminant data from EPA and ATSDR public references. This page summarizes public records — it is not a compliance determination. Methodology →
Last updated: 2025-01-10