Marin County, California
33 ZIP codes · Avg score 74/100 · Grade B · Updated 2026-06-03
Marin County — 33 ZIP codes, above-average safety grade.
How Marin County Compares
How Marin County Compares
Marin County scores 1 points above the California state average (73/100) and 6 points above the national average (68/100).
Data: EPA SDWIS Last verified: 2026-06-03
ZIP Code Risk Map
Water Quality Map: Marin County, California
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Key Risk Factors
Health risk index: 10.8 (asthma 9.4%, diabetes 10.2%)
Estimated additional annual cost per homeowner: $3,592, driven primarily by sea_level
Infrastructure: 0.401% avg pipe failure probability, 50% of ZIPs at high risk
81.5% of homes built before 1978 (lead paint era)
Violation History (2021–2024)
→ Stable trendEPA violation counts by year across Marin County water systems. Health-based shown in red, total in blue.
Peak year: 2021 with 10 violations. Past 5 years: 27 total (27 health-based).
Source: EPA SDWIS historical violations. Data may lag 6–12 months for the most recent year.
County Health Indicators vs National Average
Black markers indicate national averages. Source: CDC PLACES, Census ACS.
Infrastructure Overview
Sources: Census ACS (housing age), EPA SDWIS (infrastructure risk model), state bridge inspection data.
Compound Risk Breakdown
Estimated additional annual cost per homeowner: $3,592
Bar widths proportional to share of total annual risk cost. Source: compound risk model (FEMA, EPA, USGS).
Housing Age Distribution
83,869 housing units in Marin County
Source: U.S. Census Bureau ACS B25034 (Year Structure Built).
Water Safety Affordability
How much it costs to fix water issues relative to home values in Marin County
Remediation costs are relatively manageable for most homeowners in Marin County, representing a small fraction of property value.
Remediation includes water filtration, lead abatement, radon mitigation, and flood protection where applicable. Source: Census ACS, EPA SDWIS.
Health Outcomes vs National Average
CDC PLACES data for Marin County residents
Black markers = national averages. Red = above national avg. Green = below. Source: CDC PLACES, Census ACS.
Water Systems with Most Violations
Top 5 systems in Marin County ranked by EPA violation count.
| # | Water System | Population | Violations |
|---|---|---|---|
| 1 | City of Colusa | 6,447 | 19 |
| 2 | Colusa Company Wwd #1 - Grimes | 512 | 19 |
| 3 | NORTH MARIN WATER DISTRICT | 61,691 | 12 |
| 4 | North Marin Water District - Pt. Reyes | 1,841 | 10 |
| 5 | Rincon Valley Mobile Estates | 460 | 10 |
17 total water systems serve Marin County.
All ZIP Codes in Marin County
33 ZIP codes tracked in Marin County.
| # | ZIP Code | City | Safety Score | Grade | Violations | Home Value |
|---|---|---|---|---|---|---|
| 1 | 94966 | Sausalito | 95 | A | 0 | — |
| 2 | 94929 | Dillon Beach | 94 | A | 2 (2 health) | $1564K |
| 3 | 94946 | Nicasio | 94 | A | 1 (1 health) | $2000K |
| 4 | 94977 | Larkspur | 91 | A | 1 | — |
| 5 | 94937 | Inverness | 88 | A | 1 | $1537K |
| 6 | 94971 | Tomales | 88 | A | 0 | $880K |
| 7 | 94976 | Corte Madera | 87 | A | 0 | — |
| 8 | 94965 | Sausalito | 85 | A | 0 | $1493K |
| 9 | 94924 | Bolinas | 80 | B | 0 | $2000K |
| 10 | 94939 | Larkspur | 79 | B | 1 | $2000K |
| 11 | 94904 | Greenbrae | 78 | B | 1 | $2000K |
| 12 | 94956 | Point Reyes Station | 78 | B | 0 | $2000K |
| 13 | 94925 | Corte Madera | 77 | B | 0 | $1702K |
| 14 | 94970 | Stinson Beach | 75 | B | 1 | $1458K |
| 15 | 94915 | San Rafael | 73 | B | 0 | — |
| 16 | 94938 | Lagunitas | 73 | B | 0 | $1005K |
| 17 | 94940 | Marshall | 73 | B | 0 | — |
| 18 | 94942 | Mill Valley | 73 | B | 0 | — |
| 19 | 94950 | Olema | 73 | B | 0 | — |
| 20 | 94963 | San Geronimo | 73 | B | 0 | $1221K |
| 21 | 94973 | Woodacre | 73 | B | 0 | $1111K |
| 22 | 94948 | Novato | 68 | C | 2 (1 health) | — |
| 23 | 94998 | Novato | 68 | C | 2 (1 health) | — |
| 24 | 94949 | Novato | 66 | C | 2 (1 health) | $1076K |
| 25 | 94964 | San Quentin | 66 | C | 0 | — |
| 26 | 94974 | San Quentin | 66 | C | 0 | — |
| 27 | 94933 | Forest Knolls | 65 | C | 0 | $886K |
| 28 | 94945 | Novato | 61 | C | 2 (1 health) | $1094K |
| 29 | 94920 | Belvedere Tiburon | 60 | C | 0 | $2000K |
| 30 | 95950 | Grimes | 58 | C | 19 (16 health) | — |
| 31 | 94947 | Novato | 56 | C | 2 (1 health) | $995K |
| 32 | 94903 | San Rafael | 55 | C | 0 | $1149K |
| 33 | 94941 | Mill Valley | 55 | C | 0 | $1990K |
Recommended Buyer Guides for Marin County
While many sites publish identical guide lists across every county they cover, the selection here changes by location — driven by the EPA, NSF, FEMA, and CDC datasets that describe the actual conditions documented for this jurisdiction in the federal record.
- Best Lead Paint Test Kits — 81.5% of homes built before 1978
- Best Under-Sink Reverse Osmosis Systems — Multi-contaminant removal at the kitchen tap
Deep Dive Reports
Detailed analysis for Marin County, California
Overview
Marin County in California covers 33 ZIP codes with an average Home Safety Score of B (74/100).
13 of 33 ZIP codes have recorded EPA violations. 24 health-based violations have been documented.
← Back to California water quality report
Data Sources
- Water quality: EPA Safe Drinking Water Information System (SDWIS)
- Home values: U.S. Census Bureau ACS (median estimates by ZCTA)
Updated daily.