Water Quality

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Algal Blooms Affect Water Taste and Odor

Algae that grows in the Delta can cause drinking water to taste and smell earthy or musty. Zone 7 Water Agency's treatment processes ensure the water is safe to drink and meets all state and federal standards. Algal blooms occur most often in warm weather and usually clear up naturally within a week or two.

When water-borne algae are present in the water coming into its treatment plants, Zone 7 adds powdered activated carbon. This treatment reduces unpleasant taste and odor, but is not 100 percent effective. Zone 7 is upgrading its plants by adding ozone treatment over the next few years. Ozone is significantly more effective than other treatment technologies at treating algal byproducts that cause the unpleasant taste and odor.

For more information, read Zone 7's fact sheet on Taste and Odor Due to Algae and see the Water Quality FAQs below.

How We Monitor Drinking Water for Safety

Water utility worker, standing by pickup truck, looks at water sample in small bottle.Federal and state regulations require close monitoring of all water supplies. The water the district supplies to customers meets or exceeds all primary and secondary drinking water standards.

Many people work every day to protect the quality of our water. DSRSD employees collect representative samples from 60 locations throughout the water distribution system. The district’s laboratory, which is certified by the State Water Board Division of Drinking Water’s Environmental Laboratory Accreditation Program, analyzes the samples. Zone 7 also monitors water quality continuously online, as well as with instantaneous, or “grab,” sampling. In all, DSRSD and Zone 7 test for more than 100 water quality standards, including coliform bacteria, minerals, metals, fluoride, residual amounts of chlorine used as a disinfectant, and many other chemicals.

DSRSD publishes a water quality report by June 30th each year that summarizes water quality monitoring results from the previous calendar year. We notify all customers when the report is available in our online library. To request a printed copy, call Customer Service at (925) 828-8524. Zone 7 also publishes an annual Consumer Confidence Report.

  • Water Quality FAQs

    • What is being done to improve water taste and address blue-green algae?

    • Does our tap water contain fluoride?

    • Does our water meet safety standards for chromium 6?

    • How hard is our water?

    • How often is water tested?

    • Is our water tested for lead?

    • What do I do if I have problems with my water or other questions?

    • What do you advise about water softeners?

    • What is being done to improve water hardness?

    • Why does our water taste different than EBMUD's?

    • Why does the taste of our tap water sometimes change?

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