Skip to main content

San Mateo, CA Tap Water Quality

Water safety reports for all 5 ZIP codes in San Mateo, California

Average Score

66/100

Health Violations

15

ZIP Codes

5

High Lead Risk

4

of 5 ZIP codes

C

About Tap Water in San Mateo, CA

Water quality in San Mateo, CA is currently rated with a moderate C grade (average score: 66/100 across 5 ZIP codes). This rating indicates that while the water provided by Lazy B Mobilehome Park is treated and regulated, there have been notable compliance issues or contaminant detections recently. Residents should stay informed about the specific challenges affecting their local supply.

The accumulation of 15 health-based violations over the past 5 years highlights systemic challenges within San Mateo's water infrastructure. When violations occur, it means that drinking water tests revealed contaminant levels exceeding safe limits, triggering mandatory corrective actions by California State Water Resources Control Board. The city relies on ground water, which may require significant treatment upgrades to address these recurring issues.

Additionally, lead exposure risk remains a critical issue for certain neighborhoods. EPA data indicates that 4 out of 5 ZIP codes in San Mateo are rated as High or Very High risk for lead. This risk is often driven by aging homes with pre-1986 plumbing containing lead solder or service lines. Families in these areas should test their tap water and consider NSF/ANSI 53 certified filters.

⚠ Lead Risk Alert: Some ZIP codes in San Mateo are rated High or Very High for lead exposure risk based on EPA data. Search your specific ZIP code for a detailed lead level report.

Health-Based Contaminant Violations in San Mateo

EPA records indicate that the following contaminants have exceeded Safe Drinking Water Act Maximum Contaminant Levels (MCLs) in San Mateo water systems over the past 5 years.

LeadStage 2 DBP Rule

Note: The presence of a past violation does not necessarily mean current water is unsafe. Utilities are required to take corrective action. Review your Consumer Confidence Report for the latest status.

Frequently Asked Questions — San Mateo Water Quality

Is tap water safe to drink in San Mateo, CA?+
Tap water in San Mateo has a grade of C, indicating compliance concerns in recent years. Families with young children or pregnant women should consider using a certified NSF/ANSI 53 water filter for drinking and cooking.
What is the water quality score for San Mateo?+
The average water quality score across 5 ZIP codes in San Mateo, CA is 66/100. Scores are derived from EPA violation history, lead levels, enforcement actions, and infrastructure risk indicators. Individual ZIP codes may vary — search your specific ZIP above for a personalized report.
Does San Mateo have lead in its tap water?+
4 out of 5 ZIP codes in San Mateo are rated High or Very High for lead exposure risk. Older homes built before 1986 may have lead service lines or plumbing fixtures. Residents should run their tap for 30 seconds before use and consider a certified NSF/ANSI 53 lead filter.
How do I get the water quality report for San Mateo?+
Each ZIP code in San Mateo has a full water quality report on this site — click any ZIP code below. You can also get the annual Consumer Confidence Report (CCR) from your local water utility. The CCR is required to be published every year by July 1 and contains actual contaminant measurements and violation history.
Where does San Mateo's tap water come from?+
Tap water in San Mateo, CA primarily comes from ground water. Groundwater systems pump water from underground aquifers, which is naturally filtered through soil and rock but can still contain naturally occurring contaminants.

Looking for water quality in other cities in California?

View All Cities in California