Water Quality in San Carlos, CA: No Violations — Grade D
Grade D · Score 50/100 · 1 water system · Updated 2026-05-03
San Carlos's water has significant violations. Water testing and filtration are recommended.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
Every water system supplying San Carlos, CA appears in federal EPA tracking — and all 1 carry a violation-free record with no MCL exceedance, no reportable monitoring failures, and no active enforcement actions on file in any compliance period.
Water Quality by ZIP Code in San Carlos
Water quality varies across San Carlos's 1 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 94070 | D | 50 | 0 | 0 | View report → |
Water Quality Overview
San Carlos, California receives a water quality grade of D with an overall score of 50 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 1 water system serving San Carlos. This is a positive indicator, though it does not guarantee the absence of all contaminants — some substances (like PFAS) are not yet fully regulated.
What Grade D Means
A grade of D indicates significant compliance issues. San Carlos's water systems have accumulated violations that suggest ongoing water quality challenges. Residents should check their specific ZIP code report and consider water testing or filtration.
Lead Levels
Lead testing data for San Carlos is currently being collected. The EPA requires all community water systems to test for lead under the Lead and Copper Rule.
With 85% of homes built before 1986, San Carlos has a higher-than-average risk of lead from older plumbing. Lead solder was banned in 1986, and homes built before this date may have lead in pipes, solder joints, or fixtures.
Radon Risk
San Carlos is in EPA Radon Zone 2 (Moderate risk). Testing is recommended, especially for homes with basements or ground-level living spaces.
Water Systems Serving San Carlos
San Carlos is served by 1 community water system regulated under the Safe Drinking Water Act. These systems collectively serve approximately 30,609 people across 1 ZIP codes.
Each water system is identified by a Public Water System ID (PWSID) and is required to:
- Test for over 90 regulated contaminants on a regular schedule
- Report results to the EPA and state regulators
- Issue an annual Consumer Confidence Report (CCR) to all customers
- Take corrective action when violations occur
How to Check Your Water in San Carlos
Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels, violation history, and safety scores
Request your CCR — your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants
Get a home test — certified kits cost $20–$50 and test for lead, bacteria, and common contaminants. Professional lab tests ($150–$400) cover a broader panel
Consider filtration — NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics
Check for advisories — monitor your local utility website and local news for boil water advisories or system alerts
San Carlos vs. Nearby California Cities
How San Carlos's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| San Carlos | D | 0 | 1 | 30,609 |
| Belmont | B | 0 | 1 | 30,609 |
| Granite Bay | B | 0 | 5 | 30,607 |
| Imperial | A | 3 | 5 | 30,653 |
Common Questions About San Carlos Water
These are the most common questions residents search for about water quality in San Carlos, California:
Is San Carlos water hard or soft? Water hardness varies by source. San Carlos's 1 water system uses a single source. Check your ZIP code report for specific hardness data.
Can I drink San Carlos tap water? San Carlos's water receives a grade of D (50/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for San Carlos? A NSF/ANSI 53-certified filter for lead removal is a good general choice. See our Water Filter Matcher for personalized recommendations.
San Carlos vs. California Average
Understanding how San Carlos compares to the broader California average helps contextualize your local water quality. Factors like water source, treatment methods, and infrastructure age all contribute to differences between cities in the same state.
To see how individual neighborhoods compare, check the ZIP code reports below — water quality can vary significantly even within San Carlos.
ZIP Codes in San Carlos
San Carlos spans 1 ZIP code. Each ZIP code has its own water quality profile based on the specific water system serving that area. Check each ZIP code for detailed contaminant data, violation history, and system information.
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
- Enforcement: EPA ECHO database
- Filter recommendations: NSF/ANSI certified products
Updated daily.