Safest Drinking Water in California 2026
California has 5 public water systems serving 2,798,397 people. The safest system is East Bay MUD in Oakland with a score of 100/100.
Top 5 Water Systems in California
| # | Water System | City | Pop. Served | Source | Violations | Score |
|---|---|---|---|---|---|---|
| 1 | East Bay MUD | Oakland | 1,442,800 | Surface water | 0 | A (100) |
| 2 | Alameda County Water District | Fremont | 344,000 | Surface water | 0 | A (100) |
| 3 | CWS - Bakersfield | San Jose | 267,881 | Surface water | 0 | A (100) |
| 4 | Contra Costa Water District | Concord | 198,000 | Surface water | 0 | A (100) |
| 5 | City of Fresno | Fresno | 545,716 | Surface water | 0 | A (94) |
Water quality data for California is sourced from the EPA Safe Drinking Water Information System (SDWIS), which tracks compliance for all public water systems.
Frequently Asked Questions
East Bay MUD in Oakland has the highest Water Safety Score in California at 100/100 (Grade A), serving 1,442,800 people.
California has 5 public water systems serving 2,798,397 people. The average Water Safety Score is 99/100.
The Water Safety Score (0-100) is based on health violations (40%), contaminant exceedances (30%), enforcement history (20%), and monitoring violations (10%). Higher scores mean cleaner, safer water.
Water Safety Score: health violations (40%), contaminant exceedances (30%), enforcement history (20%), monitoring violations (10%).
The this entity category groups every U.S. public drinking-water safety entity sharing this attribute. The list above is the data; the paragraphs below explain what the grouping means against the broader the EPA Safe Drinking Water Information System (SDWIS) distribution and how to read the relative rankings within the category.
For readers using this category as a starting point, the per-entity detail pages linked from the table above carry the underlying the EPA Safe Drinking Water Information System (SDWIS) data in full. The category-level view is the filter; the per-entity pages are the actual answer.
Source: EPA Ground Water and Drinking Water, 2026.