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WaterSafeCheck

ZIP Code 94939 Water Quality Report

Larkspur, CA · Marin County County

Safety Score
B

Water Safety Grade

Good — Minor issues on record

Health Violations

0

Total Violations

1

Lead Risk

Moderate

Contaminants

0

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Active Water Quality Issues Detected

EPA records show 0 unresolved violation. Contact Marin Municipal Water District for current status.

About Tap Water in ZIP Code 94939

Tap water in ZIP code 94939 (Larkspur, CA) meets all federal safety standards and earns a solid B grade (score: 79/100). Served by Marin Municipal Water District, the water system has maintained general compliance with EPA Safe Drinking Water Act regulations, with only minor issues on record.

Water System

Marin Municipal Water District

EPA ID: CA2110002

Water Source

Surface Water

Population Served

186,895 residents

County

Marin County County, California

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Lead Levels in ZIP 94939

EPA action level: 15 ppb | Public health goal: 0 ppb

Lead Level: 7.6 ppb — Below Action Level

The 90th percentile lead level in 94939 is 7.6 ppb, below the EPA action level of 15 ppb but above what many health experts consider ideal. The CDC and EPA both affirm there is no safe level of lead exposure for children. Families with young children or pregnant women should consider a certified NSF/ANSI 53 water filter, and request lead testing of their home's tap water.

Lead exposure risk in 94939 is rated Moderate. EPA models estimate a 43% probability of lead exposure risk in this ZIP code based on housing age, infrastructure age, and water system data. This may reflect a mix of older and newer housing stock and infrastructure. Families with young children should test their home's water and consider a certified NSF/ANSI 53 water filter.

Lead Level (90th percentile)
7.60 ppb (0.0076 mg/L)
Lead Exposure Risk Rating
Moderate
Lead Exposure Probability

EPA model estimate based on housing age and infrastructure

43%
Note: Lead levels above are the 90th percentile from EPA monitoring — meaning 90% of samples were at or below this level. Even "undetected" tap water lead doesn't account for lead leaching from home plumbing. If your home was built before 1986, individual tap testing is recommended.
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Violation History

Past 5 years — EPA SDWIS data

Marin Municipal Water District has recorded 1 violation, but none are health-based. Administrative or reporting violations don't directly indicate unsafe water, but they do signal gaps in documentation or monitoring procedures.

Total Violations (5 yr)
1
Health-Based Violations
0
Unresolved Violations
0
Boil Water Advisories
0
Compliance Risk
Moderate

Regulatory compliance risk is rated Moderate. Marin Municipal Water District has had occasional lapses in compliance but generally meets Safe Drinking Water Act requirements.

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Contaminants Detected

Contaminants with health-based violations on record

No health-based contaminant violations are on record for ZIP code 94939. This means EPA monitoring has not found levels of regulated contaminants exceeding the Maximum Contaminant Levels (MCLs) set under the Safe Drinking Water Act — a positive indicator of water quality compliance.

⚖ Enforcement Actions

EPA or state regulators have issued 2 enforcement actions against Marin Municipal Water District. Enforcement actions are formal compliance orders or penalties issued when a utility fails to address violations within required timeframes.
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Water Source & Environmental Factors

Surface Water

This system draws water from lakes, rivers, or reservoirs. Surface water is treated to remove sediment, microorganisms, and chemical contaminants before reaching taps.

Water Source Type
Surface Water
EPA Radon Zone

Lower potential

Zone 3
Annual Flood Risk Cost

Estimated annual flood-related costs per property

$8
Energy Burden

% of household income spent on energy — indicator of older infrastructure

1.99%

EPA Radon Zone 3 — lower radon potential, though the EPA still recommends testing all homes.

🛡 What Should You Do? — ZIP 94939 Recommendations

  • ✓ Run cold water for 30 seconds each morning before use — especially if pipes are old
  • ✓ Request your annual Consumer Confidence Report from Marin Municipal Water District
  • ✓ If your home was built before 1986, consider testing your own tap for lead
  • ✓ Use a pitcher filter (NSF/ANSI 42 certified) for improved taste

Frequently Asked Questions — ZIP 94939 Water Quality

Is tap water safe to drink in ZIP code 94939?+
Yes — tap water in 94939 (Larkspur, CA) currently meets all federal EPA standards with a water safety grade of B. No health-based violations are on record in the past 5 years. You can drink your tap water with confidence, though running the tap for 30 seconds in the morning is always a good practice.
What is the lead level in 94939 tap water?+
The 90th percentile lead level in 94939 is 7.6 ppb (parts per billion). The EPA action level is 15 ppb. This is below the action level, but some health experts recommend a lead filter for families with young children.
Who provides tap water to 94939?+
Tap water in ZIP code 94939 is provided by Marin Municipal Water District (EPA ID: CA2110002). This system serves approximately 186,895 residents. You can contact them directly for Consumer Confidence Reports, current advisories, and billing information.
What is the water source for 94939?+
ZIP code 94939 is served by surface water. Surface water systems draw from rivers, lakes, or reservoirs and must meet strict EPA treatment requirements including filtration and disinfection.
Does 94939 have any active water quality violations?+
No active violations are on record for ZIP code 94939. EPA data shows this water system is currently in compliance with Safe Drinking Water Act standards.
How do I get a copy of my water quality report for 94939?+
Your water utility — Marin Municipal Water District — is required by law to send you an annual Consumer Confidence Report (CCR) by July 1 each year. You can also request it directly from the utility or find it online by searching "Marin Municipal Water District Consumer Confidence Report." The EPA's ECHO database also has historical compliance data.
What water filter should I use in 94939?+
The right filter depends on what contaminants are present. For lead, look for a filter certified to NSF/ANSI Standard 53. For chlorine byproducts (like THMs), NSF/ANSI 42 filters work well. For a broad range of contaminants including PFAS, look for NSF/ANSI 58 (reverse osmosis) systems. For ZIP code 94939, with a clean compliance record, a standard carbon block filter meeting NSF/ANSI 42 is a good choice for taste and as a precaution.
Is 94939 tap water safe for babies and infants?+
Infants are especially vulnerable to lead, nitrates, and microbial contaminants in drinking water. Given the detected lead level of 7.6 ppb in 94939, we recommend using a certified NSF/ANSI 53 water filter or certified bottled water for preparing infant formula. Always consult your pediatrician for guidance specific to your child's health.

Data Sources & Methodology

Water quality data for ZIP code 94939 is compiled from the EPA Safe Drinking Water Information System (SDWIS), EPA ECHO enforcement database, UCMR5 unregulated contaminant monitoring, and Consumer Confidence Reports filed by Marin Municipal Water District. Safety scores are composite metrics derived from violation history, lead levels, enforcement actions, and infrastructure risk indicators. Data reflects a 5-year monitoring window. Last dataset update: 2024. View EPA source data →