Water Quality in Modesto, CA: 5 Violations - Grade N/A

Data: EPA Safe Drinking Water Information System (SDWIS)

Water Quality Overview

Modesto, California has directly mapped EPA water-system data for 7 ZIP codes. This page reports typed compliance facts and does not relabel the multi-source Home Safety Score as a drinking-water grade.

The available EPA records report 5 violations, including 3 health-based violations across 7 directly mapped ZIP records with reported counts.

Lead Levels

The average 90th percentile lead level across Modesto water systems is 0.0120 mg/L - within EPA limits. No exceedances appear among the 7 ZIP records with known lead status.

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 10 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 5 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

1. Enter your ZIP code on ZipCheckup to see your specific water system data, including contaminant levels and violation history

2. Request your CCR - your water utility must provide an annual Consumer Confidence Report with detailed test results for all monitored contaminants

3. 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

4. Consider filtration - NSF-certified filters can remove specific contaminants. Reverse osmosis removes the broadest range; activated carbon is effective for chlorine and many organics

5. Check for advisories - monitor your local utility website and local news for boil water advisories or system alerts

Contaminants Detected in Modesto Water Systems

The following contaminants have been detected or caused violations across Modesto's water systems:

MCL = Maximum Contaminant Level (EPA enforceable standard). Health-based violations indicate levels that may pose direct health risks.

Violation Trend Over Time

Year-by-year EPA violations recorded for water systems serving Modesto:

Violation counts have remained stable over the observed period.

EPA Enforcement History

The EPA and state regulators have taken 3 enforcement actions against water systems serving Modesto. Recent actions:

Enforcement actions range from informal compliance assistance to formal orders and penalties. The most recent action was on 2026-04-10.

Modesto vs. Nearby California Cities

How Modesto's water quality compares to similar cities in California:

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

EPA coverage and recorded violations can differ across Modesto's ZIP codes. Missing counts are shown as unavailable, not zero:

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 10 water systems use multiple sources. Check your ZIP code report for specific hardness data.

Can I drink Modesto tap water? City-level EPA records cannot determine safety at a specific tap. The measured subset contains 3 health-based violations; check the affected utility record and consider certified testing.

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. EPA water-system coverage is available for 7 directly mapped ZIP codes. 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

Source reporting periods vary. See each cited source for its publication schedule.