Water Quality in Fremont, CA: 40 Violations — Grade B
Grade B · Score 78/100 · 3 water systems · Updated 2026-05-03
Fremont's water is mostly safe. Minor violations exist but are primarily monitoring-related.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-05-03
SDWIS records for Fremont, CA show 40 EPA violations documented for the local water supply — these span the full range of reportable events from health-based exceedances to monitoring and reporting lapses registered with the federal program.
Water Quality Map: Fremont, CA
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Water Quality by ZIP Code in Fremont
Water quality varies across Fremont's 5 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 94537 | B | 77 | 8 | 1 | View report → |
| 94536 | B | 78 | 8 | 1 | View report → |
| 94538 | B | 78 | 8 | 1 | View report → |
| 94539 | B | 78 | 8 | 1 | View report → |
| 94555 | B | 78 | 8 | 1 | View report → |
Water Quality Overview
Fremont, California receives a water quality grade of B with an overall score of 78 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
The 3 water systems serving Fremont have accumulated 40 EPA violations, including 5 health-based violations. These violations are tracked across 5 ZIP codes serving approximately 344,145 people.
What Grade B Means
A grade of B indicates good compliance with EPA drinking water standards. While not perfect, Fremont's water systems meet the vast majority of federal requirements. Minor violations may exist but typically relate to monitoring or reporting rather than health-based standards.
Lead Levels
The average 90th percentile lead level across Fremont water systems is 0.0053 mg/L — within EPA limits. No ZIP codes exceed the EPA lead action level.
With 68% of homes built before 1986, Fremont 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
Fremont is in EPA Radon Zone 2 (Moderate risk). Testing is recommended, especially for homes with basements or ground-level living spaces.
Water Systems Serving Fremont
Fremont is served by 3 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 344,145 people across 5 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
The EPA has taken 5 enforcement actions against water systems serving Fremont. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Fremont
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
Contaminants Detected in Fremont Water Systems
The following contaminants have been detected or caused violations across Fremont's water systems:
| Contaminant | Category | MCL | Violations | ZIPs Affected | Health-Based |
|---|---|---|---|---|---|
| Stage 1 DBP Rule | Treatment Technique | N/A | 30 | 5 | No |
| Stage 2 DBP Rule | Treatment Technique | N/A | 10 | 5 | Yes |
MCL = Maximum Contaminant Level (EPA enforceable standard). Health-based violations indicate levels that may pose direct health risks.
EPA Enforcement History
The EPA and state regulators have taken 1 enforcement action against water systems serving Fremont. Recent actions:
| Date | Action Type |
|---|---|
| 2024-02-01 | State Order Extension |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2024-02-01.
Fremont vs. Nearby California Cities
How Fremont's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Fremont | B | 40 | 3 | 344,145 |
| Newark | C | 0 | 1 | 344,000 |
| Union City | C | 0 | 1 | 344,000 |
| Alhambra | B | 0 | 5 | 344,330 |
Recommended Water Filters for Fremont
Based on contaminants detected in Fremont's water supply, these filter types are recommended:
Granular Activated Carbon (GAC, whole-house or under-sink)
- Removes: Disinfectant Residual (as Cl2)
- Effectiveness: 95-99%
- Cost range: $100–$600
- Certification: NSF/ANSI 42
- Recommended products:
- Aquasana AQ-5200
- Waterdrop Chubby Pitcher
- Berkey Travel
Granular Activated Carbon (GAC, under-sink or whole-house)
- Removes: 5 Haloacetic Acids (HAA5)
- Effectiveness: 60-80%
- Cost range: $100–$600
- Certification: NSF/ANSI 53
- Recommended products:
Granular Activated Carbon (GAC, whole-house POE)
- Removes: Total Trihalomethanes (TTHMs)
- Effectiveness: 80-99%
- Cost range: $400–$2000
- Certification: NSF/ANSI 53
- Recommended products:
Water Quality by ZIP Code in Fremont
Water quality varies across Fremont's ZIP codes. The table below shows the worst-scoring and best-scoring areas:
| ZIP Code | Score | Grade | Violations | Health-Based |
|---|---|---|---|---|
| 94537 | 77 | B | 8 | 1 |
| 94536 | 78 | B | 8 | 1 |
| 94538 | 78 | B | 8 | 1 |
| 94539 | 78 | B | 8 | 1 |
| 94555 | 78 | B | 8 | 1 |
Common Questions About Fremont Water
These are the most common questions residents search for about water quality in Fremont, California:
Is Fremont water hard or soft? Water hardness varies by source. Fremont's 3 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Fremont tap water? Fremont's water receives a grade of B (78/100). There are 5 health-based violations — consider filtration.
What is the best water filter for Fremont? Based on detected contaminants, a granular activated carbon (gac, whole-house or under-sink) filter is most recommended. See our Water Filter Matcher for personalized recommendations.
Fremont vs. California Average
Understanding how Fremont 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 Fremont.
ZIP Codes in Fremont
Fremont spans 5 ZIP codes. The ZIP with the lowest water quality score is 94536. 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.
Frequently Asked Questions
Your Water is Safe — Here's How to Keep It That Way
Grade B is excellent news. Here's what proactive homeowners do to maintain water quality:
Annual Water Testing
EPA recommends annual testing even with clean water. Home test kits: $20-$50. Catches changes before they become problems.
Maintenance Filtration
A basic carbon filter removes chlorine taste and catches emerging contaminants like PFAS that aren't yet fully regulated.
Plumbing Check
Even safe city water picks up lead from home pipes. If your home was built before 1986, a one-time pipe inspection is recommended.