The District purchases raw water from  Contra Costa Water District via the Contra Costa Canal. This raw water originates in either Rock Slough or Old River (from the San Joaquin River). Los Vaqueros Reservoir stores high-quality raw water, which is piped from Old River and can be used when needed.

Water is treated at the modern Randall-Bold Water Treatment Plant, which is jointly owned by Diablo Water District and Contra Costa Water District. The water treatment plant uses the best available technology and includes many innovations to ensure reliability and high-quality drinking water. As noted below:

• Removal of particles through sedimentation.
• Disinfection with ozone, which is more effective in eliminating bacteria than chlorine.
• Filtration through 65 inches of granular activated carbon and 10 inches of sand.
• Chloramination in minute quantities to continually disinfect the water in the pipeline until it reaches your home.
• Supervision around-the-clock by State-certified professionals using a computer-controlled monitoring system.
• Modern Day Security. The District has increased security with new physical barriers, alarms, patrols, ozone disinfection, and additional water quality testing.

Annual Water Quality Report

Each year, a water quality report is published to keep our community informed about the safety and quality of their drinking water. We’re proud to report that your water continues to meet or exceed all state and federal health standards.

As part of our mission to be environmentally responsible stewards of the water resources in our care, our Water Operations team regularly samples and monitors the water supply. Through technical innovation and a commitment to excellence, we ensure your water remains safe, reliable, and of the highest quality.

Click the link below to view the latest report and learn more about where your water comes from.

The running annual average (RAA) manganese concentration from the samples collected for Compliance Periods of Q2 2023, Q3 2023, Q4 2023, Q1 2024, Q2 2024 was 0.06, 0.08, 0.1, 0.08, and 0.06 mg/L, respectively exceeded the secondary MCL for manganese.

Note: Boron levels included in the Annual Water Quality Report are sourced from untreated well water. Treated water results for Boron are 300ug/L.

Lead Service Line Inventory - Statement of Non-Lead Inventory

The United States Environmental Protection Agency (EPA) requires water agencies to update and improve rules concerning the amount of lead in drinking water. Lead was frequently used in older household plumbing materials and certain water service lines.

Through completing historical records review and field investigations, Diablo Water
District has determined it has no lead or galvanized requiring replacement service lines
in its distribution system. This includes any privately-owned or customer-owned service
lines.

For more specific information about lead and copper in your drinking water, please visit the USEPA website.