States › California › Marin County

Marin County, CA Water Quality

Water quality data for 7 public water systems serving Marin County, California — based on EPA SDWIS enforcement records, lead testing results, and health-based violation history.

📅 2026 Report 🔄 Data updated 2026 Q2 📍 7 water systems · 30 cities
✅
Excellent — All Systems Performing Well

Water quality across the county is outstanding with minimal violations and very low lead levels.

A

Marin County Earns a A

Marin County: 30 communities across 7 water systems. 100.0% have no open violations.

  • Median lead where detected: 4.00 ppb
  • 3 communities with a lead detection, 27 reporting none detected
  • 0 communities with PFAS above the federal limit
  • 0 with significant inspection deficiencies
  • 100.0% of communities have no open violations
4 ppb
Median Lead Level
County-wide, 90th percentile
7
Water Systems
Active CWS & NTNCWS
100%
Violation-Free
No active violations on record
How we grade counties: MyWaterIQ uses EPA SDWIS enforcement data — actual MCL violations and lead test results — not the aspirational MCLG targets used by some sites. A grade reflects real compliance history, not theoretical risk. Learn more →

Cities by Water Quality

⭐ Best Performing
  • San Rafael
    Not detected
    No federal limits exceeded on record
    A
  • Mill Valley
    Not detected
    No federal limits exceeded on record
    A
  • Larkspur
    Not detected
    No federal limits exceeded on record
    A
  • San Anselmo
    Not detected
    No federal limits exceeded on record
    A
  • Tamalpais-Homestead Valley
    Not detected
    No federal limits exceeded on record
    A
⚠ Needs Attention
  • Nicasio
    4.00 ppb
    Copper above the 1,300 ppb action level
    C
  • Muir Beach
    10.00 ppb
    Copper above the 1,300 ppb action level
    B
  • Novato
    Not detected
    Copper above the 1,300 ppb action level
    A
  • Black Point-Green Point
    Not detected
    Copper above the 1,300 ppb action level
    A
  • Inverness
    Not detected
    Copper above the 1,300 ppb action level
    A
County Lead Level — Median 4 ppb
Based on most recent 90th percentile lead tests across all reporting systems
0 ppb5 ppb10 ppb15 ppb
County median: 4 ppb — 26.7% of the federal action level
Systems by Lead Level
Under 5 ppb
2
10 – 15 ppb
1
No Data
27

All Cities in Marin County

San Rafael Not detected A
Novato Not detected A
Mill Valley Not detected A
Larkspur Not detected A
San Anselmo Not detected A
Tamalpais-Homestead Valley Not detected A
Corte Madera Not detected A
Tiburon Not detected A
Fairfax Not detected A
Sausalito Not detected A
Kentfield Not detected A
Lucas Valley-Marinwood Not detected A
Strawberry Not detected A
Santa Venetia Not detected A
Marin City Not detected A
Sleepy Hollow Not detected A
Ross Not detected A
Belvedere Not detected A
Lagunitas-Forest Knolls Not detected A
Black Point-Green Point Not detected A
Bolinas Not detected A
Woodacre Not detected A
Inverness Not detected A
Alto Not detected A
Stinson Beach Not detected B
San Geronimo Not detected A
Point Reyes Station Not detected A
Muir Beach 10.00 ppb B
Dillon Beach 1.40 ppb B
Nicasio 4.00 ppb C
Showing 30 cities
No active violations Active violations

About Marin County Drinking Water

Marin County is served by 7 water systems covering 30 communities. No community here has an open violation on record.

Of the communities reporting lead results, 3 recorded a detection, with a median of 4.00 ppb — 27% of the federal action level. 27 reported none detected, which means below the laboratory limit rather than an absence of lead.

No community here has PFAS above the federal limit on record. State inspectors recorded no significant deficiencies.

Frequently Asked Questions

Is Marin County tap water safe to drink?▼
No community in Marin County has an open violation on record. No community has PFAS above the federal limit on record.
What is the lead level in Marin County?▼
Among communities with a detection the median is 4.00 ppb, 27% of the 15 ppb action level. 27 reported none detected and 0 reported no result.
How many water systems serve Marin County?▼
7 community water systems serve 30 communities here.
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