United States Last reviewed: August 28, 2026

California Tap Water Quality

Q: Is tap water safe to drink in California?

For the vast majority, yes: Los Angeles, San Francisco, San Diego, Sacramento, and the other large systems meet all federal and stricter state standards. The exceptions are small Central Valley and rural systems on contaminated groundwater, which the state tracks publicly.

Q: Why do small Central Valley towns have unsafe water?

Decades of fertilizer, dairy, and fumigant use contaminated shallow groundwater with nitrate and 1,2,3-TCP, and many tiny systems cannot afford treatment. The state's SAFER program funds fixes and consolidations.

Q: Is California tap water more regulated than other states?

Yes. California enforces its own stricter limits for contaminants like chromium-6, 1,2,3-TCP, and perchlorate, and adopted PFAS response levels ahead of federal rules.

about 2,900

Community water systems

City reports on this site

Tracked contaminants

August 28, 2026

Data reviewed

Check a California ZIP Code

Overview

California operates the largest and most scrutinized drinking water program in the country, with roughly 2,900 community systems and state standards stricter than federal minimums for several contaminants. The big city systems: LADWP, SFPUC's Hetch Hetchy supply, EBMUD, and San Diego's blended portfolio, all meet every federal and state standard.

The gap is between those systems and the small ones. Hundreds of small Central Valley communities sit on groundwater contaminated with nitrate from agriculture, arsenic, uranium, or 1,2,3-TCP, and the state's SAFER program spends hundreds of millions annually consolidating failing systems. California also pioneered regulation of chromium-6 and PFAS ahead of federal rules.

Common Contaminants in California

Nitrate

The Central Valley's signature problem: fertilizer and dairy legacy in groundwater pushes some small-system wells over the 10 mg/L limit

Arsenic

Naturally occurring in Central Valley and desert groundwater; a leading cause of small-system violations

1,2,3-TCP

A legacy fumigant contaminant regulated by California but not federally; detected in dozens of Valley systems, driving treatment installs and lawsuits against manufacturers

Chromium-6

California set the nation's first chromium-6 limit; some inland systems blend or treat to comply

PFAS

Plumes near airports, bases, and industrial areas affect wells in Orange County, the Inland Empire, and elsewhere; large-scale treatment is being built

Violations & Compliance

Roughly 300 mostly small systems appear on California's Human Right to Water failing-systems list at any time, serving under 2% of the population. The metro systems that serve most Californians are consistently compliant, and the state aggressively consolidates failing systems into larger neighbors.