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The Metropolitan Water District of Southern California

Quality & Treatment

Water Quality​

For more than 80 years, Metropolitan has been Southern California's provider of high quality, reliable drinking water that meets or exceeds all federal and state drinking water regulations. Using advanced treatment technologies increased monitoring and adhering to stringent laws and guidelines, Metropolitan works hard to protect the quality of water delivered to the consumer.

To ensure the delivery of a safe and reliable water supply, Metropolitan operates five water treatment plants. On an ongoing basis, Metropolitan tests its water for nearly 400 constituents and performs about 250,000 water quality tests per year on samples gathered from throughout its vast distribution system. Analysis of these samples is undertaken at Metropolitan's state-of-the art water quality laboratory.



Treatment Facilities

Metropolitan owns and operates five treatment plants that are located throughout Metropolitan's six-county service area and that treat water delivered from the State Water Project and the Colorado River. Four of these plants –F.E. Weymouth, Robert A. Skinner, Robert B. Diemer and Joseph Jensen – are among the 10 largest in the world.

Notice to Potentially Affected Public Agencies

Metropolitan's notification of treatments to control nuisance algae blooms may occur at the following water supply reservoirs: Lake Skinner, Lake Mathews, and Diamond Valley Lake.  Click here to read the notice.