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For Major Leaks and Other Urgent Water Issues Please Call (925) 625-3798
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Open Monday - Friday
8:00 a.m. - 12:00 p.m.
1:00 p.m. - 5:00 p.m.
Closed 12:00 p.m. - 1:00 p.m.
87 Carol Lane, Oakley, CA
Phone: (925) 625-3798
Fax: (925) 625-0814
Mail: P.O. Box 127
  Oakley, CA 94561-0127
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Water Quality

Diablo Water District starts with a high quality water supply and then subjects it to intensive treatment and testing, ensuring our customers the best possible quality of drinking water that meets or is better than all state and federal water quality standards.


Our Intensive Water Quality Process

Blending Facility

Testing Ensures High Quality Water

Notice for Fish Tank Owners and Those on Kidney Dialysis


Your water is treated at the Randall-Bold Water Tratment Plant, which is jointly owned by Diablo Water District and Contra Costa Water District

Your water is treated at the Randall-Bold Water Tratment Plant, which is jointly owned by Diablo Water District and Contra Costa Water District.

Our Intensive Water Quality Process

The District purchases raw water from the 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.

Blending Facility

The District built a blending facility near the Randall-Bold Water Treatment Plant to blend well water with treated water from the Randall-Bold Water Treatment Plant. This creates a cost-effective, high quality water supply for delivery to our customers. The well, the first practical source of local groundwater, is connected to the blending facility by a 3.5-mile-long pipeline.

Testing Ensures High Quality Water

Before delivery to your home or business, our water undergoes testing by State-certified water quality operators. Your water is monitored 24 hours a day, 7 days a week, to ensure that high quality water is available to you. The tests are done with such extraordinary accuracy that we can detect one hundredth of a part of a substance in a billion parts of water. This is equivalent to finding one drop of a substance in 1,300,000 gallons of water.

Tests are conducted daily, weekly, monthly and annually. With today?s sophisticated equipment, water can be monitored continuously. Once a year, the District issues a water quality report, which is called the Annual Consumer Confidence Report. In this report you are able to review the water testing results. You can view copies of the current and past Consumer Confidence Reports by clicking on the links below:

All Consumer Confidence Reports are in PDF format and require the free Adobe Reader. * Tip - Right click on links and select " Save Target As".

Current Annual Water Quality Report July 2015

Archived Annual Water Quality Reports
July 2016
July 2014
July 2013
July 2012
July 2011
July 2010
July 2009
July 2008
July 2007
July 2006
July 2005
July 2004
July 2003

Notice for Fish Tank Owners

The District uses chloramines to disinfect your drinking water supply and keep it safe. Chloramines are a long-lasting, safe disinfectant that is becoming increasingly popular across the country. Chloramines are toxic for fish. If you are using tap water, you should assure that the fish are properly protected. Local pet shops can advise you on the best measures to neutralize chloraminated water.

Notice for Those on Home Kidney Dialysis

The District uses chloramines to disinfect your drinking water supply and keep it safe. Chloramines are a long-lasting, safe disinfectant that is becoming increasingly popular across the country. While chloramines pose no health hazard to the general public, people undergoing home kidney dialysis treatment should consult their physician before using the water in the dialysis unit.