San Geronimo, CA Water Safety: 73/100 (2026)
1 ZIP code · 2 water systems · Updated 2026-06-03
Drinking water tracked for San Geronimo by CA authorities posts above-average scores — the majority of systems are free from health-based exceedances and the city's grade sits above the state median.
How San Geronimo Compares
Data: EPA SDWIS Last verified: 2026-06-03
Key Facts for San Geronimo Residents
- Homes built before 1986: 67% — older plumbing may contain lead solder.
- Estimated remediation: $1,200 per household.
- CDC health risk index: 10.78.
San Geronimo's Water Providers
2 water utilities share the residential service territory in San Geronimo, CA — out of 2 total systems in federal records.
Overview
We track water quality and home safety data for 1 ZIP code in San Geronimo, California (population ~562), covering 2 community water systems serving approximately 186,931 people region-wide.
No EPA violations recorded across any ZIP codes in San Geronimo — an excellent indicator of water quality.
Home Safety Score
Average Home Safety Score for San Geronimo: B (73/100)
The score combines three factors:
| Factor | What It Measures |
|---|---|
| Water Quality | EPA violations and compliance history |
| Lead Levels | 90th percentile lead concentration vs EPA action level |
| Radon Risk | EPA radon zone classification |
Water Sources
San Geronimo water systems draw from: Groundwater.
Lead & Copper
- Lead data: not yet available for San Geronimo
- 0 ZIP codes exceed the EPA lead action level
Radon Risk
Dominant radon zone: Zone 3 (Low Risk)
Areas with No Violations
| ZIP Code | Safety Score | System | Population |
|---|---|---|---|
| 94963 | B | Marin Municipal Water District | 186,895 |
All ZIP Codes in San Geronimo
- 94963 [B]
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Lead/copper: EPA Lead and Copper Rule sampling data
- Radon: EPA Map of Radon Zones
Updated daily.
San Geronimo Community Health Snapshot
Source: CDC PLACES (County-level estimates). Water contamination can correlate with respiratory and chronic health conditions.
Compared to National Average
Vertical line = national average. ■ Above national · ■ Below national
San Geronimo Infrastructure Age
With 67% of homes built before 1986, lead solder in plumbing is a potential concern. The EPA banned lead solder in 1986, but many older homes retain original plumbing.
Source: U.S. Census Bureau American Community Survey (ACS).
Housing Age Profile
While newer cities carry lower aggregate plumbing risk from lead-era construction, San Geronimo sits firmly in the older category. The median build year of 1964 indicates that more than half the housing stock was built before 1986, when lead solder was still legally used in residential copper plumbing — and a substantial portion likely predates 1970, when lead pipes were still commonly installed for service lines. These two thresholds together define the elevated plumbing risk environment that older housing cities carry, independent of what the municipal water supply delivers to the meter.
Over half of homes in San Geronimo were built before 1986, when lead solder was banned. Older plumbing may leach lead into drinking water, especially with corrosive water chemistry.
Source: U.S. Census Bureau ACS B25034.
How Remediation Costs Compare in San Geronimo
In San Geronimo, property values comfortably outpace what documented remediation typically costs — the equity share is proportionally low.
Remediation costs in San Geronimo are relatively low compared to home values. The $800–$1,800 estimated range is a small fraction of median property value. Home values are 65% above the California average.
San Geronimo: Lead Risk & Vulnerable Populations
Why children are most at risk: The CDC states there is no safe level of lead exposure for children. Children under 6 absorb lead more readily than adults, and even low levels can cause developmental delays, learning difficulties, and behavioral problems.
Wherever 67% of local housing was built before solder rules changed — as is the case in San Geronimo — a faucet-level sample closes the gap that aggregate utility data cannot.
Sources: EPA Lead and Copper Rule, U.S. Census Bureau ACS, CDC childhood lead poisoning prevention guidelines.
San Geronimo: Flood History & Water Damage Risk
Flood history in San Geronimo spans 7 NFIP claims and 100% flood zone coverage — enough to place it in moderate-exposure territory where flood events are genuinely recurring rather than statistical outliers. That distinction matters for water quality assessment because the connection between flooding and water safety is not uniform across communities. In low-exposure areas, flooding rarely generates the conditions needed to compromise treatment or distribution infrastructure. In high-exposure areas, it can do so repeatedly. Moderate-exposure communities sit in between: flood events occur with enough frequency to make periodic infrastructure stress a reasonable concern, particularly for private well owners and residents in lower-elevation FEMA-designated zones.
San Geronimo has a moderate flood history with 7 FEMA claims averaging $4,148 per payout. 100% of ZIP codes fall within FEMA flood zones. Flood events can contaminate drinking water and overwhelm treatment systems.
How flooding affects water quality: Flood events can introduce sewage, agricultural runoff, and industrial chemicals into water supplies. Even after floodwaters recede, contamination can persist in wells and aging infrastructure. Flood damage can add significantly to the estimated <strong>$1,200</strong> remediation cost per household.
Residents in flood-prone areas should consider flood insurance even outside FEMA zones — over 25% of flood claims come from low-to-moderate risk areas. After any flood event, test your water before drinking.
Source: FEMA National Flood Insurance Program (NFIP) claims data, FEMA flood zone designations.
Deep Dive Reports
Detailed analysis for San Geronimo, CA