Is Tap Water Safe to Drink in Modesto?
Yes, tap water in Modesto is safe to drink. The city blends treated Tuolumne River water from the Modesto Irrigation District with local groundwater, and served water meets EPA and California standards.
Water Source
Modesto receives Sierra-fed Tuolumne River water treated at the Modesto Regional Water Treatment Plant (via Modesto Reservoir, operated with the Modesto Irrigation District), blended with city groundwater wells in the Central Valley aquifer.
EPA Compliance Status
Meets all federal Safe Drinking Water Act standards and California's stricter state limits.
Notable Contaminants & Context
- •1,2,3-TCP, a legacy soil fumigant impurity found across Central Valley groundwater, prompted treatment or removal of affected wells to meet California's strict standard
- •Nitrate from decades of regional agriculture appears in parts of the aquifer and is managed by blending with clean river water and well management
- •Trace naturally occurring uranium and arsenic at scattered wells are treated or blended below limits
Water Quality Data
Key contaminants detected vs. regulatory limits. All values from the most recent published report — Source: City of Modesto Water Division 2024 CCR.
| Contaminant | Detected | Limit | Status |
|---|---|---|---|
| Chlorine (total) | 0.7 mg/L | 4.0 mg/L | ✓ |
| Fluoride | 0.71 mg/L | 4.0 mg/L | ✓ |
| Lead (90th percentile) | 2.0 µg/L | 15.0 µg/L | ✓ |
| Nitrate (as N) | 4.1 mg/L | 10.0 mg/L | ✓ |
| TTHM (Total Trihalomethanes) | 13.6 µg/L | 80.0 µg/L | ✓ |
| HAA5 (Haloacetic Acids) | 8.9 µg/L | 60.0 µg/L | ✓ |
| Chromium-6 | 0.14 µg/L | 0.02 µg/L | ⚠ |
✓ = below limit ⚠ = above health goal ✗ = exceeds guideline
How It Compares
Modesto's move toward more Sierra surface water was partly a quality play: Tuolumne River water is far cleaner than Valley groundwater, diluting the agricultural legacy contamination common to the region.
Tips
- •Taste varies between surface-water and well-served neighborhoods
- •California requires public notification for any exceedance — check the city's annual Consumer Confidence Report
- •A carbon filter is optional for taste, not required for safety
Frequently Asked Questions
Sources & References
The safety rating and guidance on this page draw on the following sources. See our full methodology.
- •US EPA Safe Drinking Water Act regulations
- •EWG Tap Water Database
- •The utility's most recent Consumer Confidence Report (CCR)
- •WHO Guidelines for Drinking-water Quality