Water quality · ZIP 94131
Water quality in San Francisco (Twin Peaks), CA
ZIP 94131 (California) — water quality summary sourced from EPA SDWIS. Data lands this week as the EPA SDWIS ingestion pipeline rolls out.
Last verified 2026-04-24 · 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). Stale data is flagged, never silently served. Primary source →
Limitations specific to this source
Where a ZIP is served by multiple water systems, zipradar shows the dominant CWS by population served and lists alternates. Private well water is not covered.
California context
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.
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Plain-English guide to FEMA flood-zone codes (A, AE, AH, V, VE, X, X-shaded). What the 1% and 0.2% annual-chance zones mean for your property and your insurance.
EPA Radon Zones — what 1, 2, and 3 mean and when you should test
EPA classifies every US county into Zone 1 (high), Zone 2 (moderate), or Zone 3 (low) for radon. Plain-English guide to the classifications and at-home testing.
Lead and Copper Rule 2024 — the federal lead-pipe inventory mandate
The 2024 Lead and Copper Rule Revisions (LCRR) require every US community water system to inventory and report lead service lines. Plain-English guide.
AQI explained — what 50, 100, 150 actually mean for your lungs
Plain-English guide to the EPA Air Quality Index (AQI) and the 6 categories from Good to Hazardous. When to take precautions and which pollutants matter.
Full dashboard for ZIP 94131
Water quality is one of twelve dimensions zipradar federates per address. See the full federated summary for ZIP 94131:
Open San Francisco (Twin Peaks), CA dashboard →