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Water quality · California

Water quality in California

Water quality (EPA SDWIS) data for ZIP codes in California. Pick a ZIP below to dive into the water quality summary.

Last verified 2026-05-13 · methodology

What lands here

Pages show the CWS serving the address, any health-based violations in the last 3 years, most recent lead and copper sampling result, and a link to the primary SDWIS record.

Source & refresh

EPA SDWIS. Refreshed quarterly (federal mandate). Primary source →

California top concern

Wildfire (WUI), seismic, water-supply variability

California carries the highest concentrated WUI wildfire risk in the US per USFS WHP, with FAIR Plan + non-renewal pressure intensifying since 2017 fires. FEMA NFHL coverage is strong; drinking-water systems vary from large urban (LADWP, EBMUD) to small disadvantaged community systems flagged in EPA SDWIS. Radon risk is mostly Zone 2-3.

See California state page for the full state-level rollup across all 12 dimensions.

Read more on water quality

Editorial deep-dives explaining the source data, its limits, and how to read it.

29 California ZIPs