Water Quality in Modesto, CA: No Violations - Grade A
Grade A · Score 95/100 · 8 water systems · Updated 2026-07-18
Modesto's water meets all EPA standards with no health-based violations.
Data: EPA Safe Drinking Water Information System (SDWIS) Last verified: 2026-07-18
Modesto, CA has zero reported violations - 8 water systems, all compliant.
Water Quality Map: Modesto, CA
Each dot represents a ZIP code. Color indicates water quality grade. Tap a dot for details.
Water Quality by ZIP Code in Modesto
Water quality varies across Modesto's 10 ZIP codes. Check your specific ZIP for detailed contaminant data.
| ZIP Code | Grade | Score | Violations | Health | |
|---|---|---|---|---|---|
| 95351 | A | 90 | 0 | 0 | View report → |
| 95354 | A | 90 | 0 | 0 | View report → |
| 95358 | A | 90 | 0 | 0 | View report → |
| 95350 | A | 95 | 0 | 0 | View report → |
| 95353 | A | 95 | 0 | 0 | View report → |
| 95355 | A | 95 | 0 | 0 | View report → |
| 95357 | A | 95 | 0 | 0 | View report → |
| 95352 | A | 99 | 0 | 0 | View report → |
| 95356 | A | 99 | 0 | 0 | View report → |
| 95397 | A | 99 | 0 | 0 | View report → |
Violation Trend
EPA violations recorded for water systems serving Modesto.
Water Quality Overview
Modesto, California receives a water quality grade of A with an overall score of 95 out of 100, based on EPA compliance data from the Safe Drinking Water Information System (SDWIS).
No EPA violations have been recorded for the 8 water systems serving Modesto. 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 A Means
A grade of A indicates excellent compliance with EPA drinking water standards. Modesto's water systems have maintained strong performance in both contaminant monitoring and regulatory compliance.
Lead Levels
The average 90th percentile lead level across Modesto water systems is 0.0006 mg/L - within EPA limits. No ZIP codes exceed the EPA lead action level.
With 67% of homes built before 1986, Modesto 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.
Water Systems Serving Modesto
Modesto is served by 8 community water systems regulated under the Safe Drinking Water Act. These systems collectively serve approximately 268,575 people across 10 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 4 enforcement actions against water systems serving Modesto. Enforcement actions range from informal compliance assistance to formal orders and penalties.
How to Check Your Water in Modesto
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
Violation Trend Over Time
Year-by-year EPA violations recorded for water systems serving Modesto:
| Year | Total Violations | Health-Based |
|---|---|---|
| 2021 | 2 | 2 |
| 2024 | 1 | 1 |
Violations have decreased from 2 in 2021 to 1 in 2024, indicating improving compliance.
EPA Enforcement History
The EPA and state regulators have taken 2 enforcement actions against water systems serving Modesto. Recent actions:
| Date | Action Type |
|---|---|
| 2023-10-06 | State Order Extension |
| 2021-12-10 | State Filed Suit |
Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2023-10-06.
Modesto vs. Nearby California Cities
How Modesto's water quality compares to similar cities in California:
| City | Grade | Violations | Systems | Population |
|---|---|---|---|---|
| Modesto | A | 0 | 8 | 268,575 |
| Chula Vista | A | 0 | 4 | 272,064 |
| Corona | B | 7 | 10 | 262,651 |
| San Bernardino | B | 0 | 17 | 255,071 |
Recommended Water Filters for Modesto
Based on contaminants detected in Modesto's water supply, these filter types are recommended:
Reverse Osmosis (under-sink)
- Removes: Arsenic, Nitrate (as Nitrogen, N), Gross Alpha, Uranium
- Effectiveness: 90-99%
- Cost range: $150–$500
- Certification: NSF/ANSI 58
- Recommended products:
- Waterdrop G3P800
- iSpring RCC7AK
- Crystal Quest Arsenic Filter
Water Quality by ZIP Code in Modesto
Water quality varies across Modesto's ZIP codes. The table below shows the worst-scoring and best-scoring areas:
| ZIP Code | Score | Grade | Violations | Health-Based |
|---|---|---|---|---|
| 95351 | 90 | A | 0 | 0 |
| 95354 | 90 | A | 0 | 0 |
| 95358 | 90 | A | 0 | 0 |
| 95350 | 95 | A | 0 | 0 |
| 95353 | 95 | A | 0 | 0 |
| 95355 | 95 | A | 0 | 0 |
| 95357 | 95 | A | 0 | 0 |
| 95352 | 99 | A | 0 | 0 |
| 95356 | 99 | A | 0 | 0 |
| 95397 | 99 | A | 0 | 0 |
Common Questions About Modesto Water
These are the most common questions residents search for about water quality in Modesto, California:
Is Modesto water hard or soft? Water hardness varies by source. Modesto's 8 water systems use multiple sources. Check your ZIP code report for specific hardness data.
Can I drink Modesto tap water? Modesto's water receives a grade of A (95/100). No health-based violations have been recorded, but home testing is always recommended.
What is the best water filter for Modesto? Based on detected contaminants, a reverse osmosis (under-sink) filter is most recommended. See our Water Filter Matcher for personalized recommendations.
Modesto vs. California Average
Understanding how Modesto 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 Modesto.
ZIP Codes in Modesto
Modesto spans 10 ZIP codes. 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 A 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.