California Water Quality Report 2026: 398 Cities Ranked by the Records

PurityMap does not give a statewide safe or unsafe verdict: California tap water comes from many separate public water systems, so the answer depends on the one that serves you. Of 398 California city reports, 15 cities have a health-based violation in the federal SDWIS record in the last 10 years, and 1 city was above the 15 µg/L lead action level. 113 of 398 California city reports had a PFAS sample above a 2024 EPA limit. EPA's 2024 limits are judged on a yearly average, and water systems have until 2029 to meet them, so a single sample is not a violation. 273 of 398 have none of these on record, which is not the same as every contaminant being tested. Your city's report shows its own records, and plumbing inside a building can still change what reaches your tap.

175 California cities share the top place in the ranking. The largest of them by population served are Oakland, San Diego, San Francisco, Irvine and Fremont. Cities are ranked by the Purity Score of each one's main water system, computed only from contaminants measured in the published EPA record, so the ranking compares the records, not which city's water is safest. Each city report names the water system behind its score.

PurityMap ranks 398 cities in California by the Purity Score of each city's main water system, computed only from contaminants measured in the published EPA record. Scores belong to water systems, not to cities. The highest published score is Oakland's main water system: EAST BAY MUD · PWSID CA0110005 · Purity Score 100 (Excellent) · Confidence: moderate · Assessed at the water-system level. The ranking compares the records, not which city's water is safest, and your own tap can differ with household plumbing.

113 of 398 California city reports had a PFAS sample above a 2024 EPA limit in EPA's UCMR 5 testing, including Atwater (PFOS 45 ng/L), Downey (PFOS 44 ng/L), Sacramento (PFOS 41.4 ng/L). That limit is judged on a yearly average, and water systems have until 2029 to meet it, so a single sample is not a violation. PFAS were detected at any level in 153.

Utilities report lead as a 90th-percentile result from home taps. 109 of 398 California cities reported a value above zero, and 1 city was above the 15 µg/L federal action level. Lead usually comes from a building's own pipes and fixtures, so only a test at your tap tells you what you drink.

15 cities in California have a health-based violation in the federal SDWIS record within about the last ten years. Each city report lists the contaminant, year and whether it was resolved.

Hardness is published in utility water-quality reports for 44 California cities on record; the hardest is Oxnard at 24.5 grains per gallon. Hardness affects scale and appliances; it is not a health finding.