Water Quality

The delivery of safe water to the San Diego County Water Authority's 24 retail member agencies and their customers is the top priority for the Water Authority. Regular water quality monitoring and the use of online monitoring equipment ensure that the Water Authority is delivering high-quality, safe water to its member agencies 24 hours a day, seven days a week.


April 21-22 Water Treatment Citation

A malfunction at the Twin Oaks Valley Water Treatment Plant on April 21-22, 2019, resulted in a citation from the state Division of Drinking Water. The water in regional pipelines continued to be safe for all uses due to additional treatment processes that are in place. Corrective actions were taken immediately, and the lapse was reported to state regulators. The contractor has updated its operational procedures and installed additional monitoring equipment to prevent similar problems in the future.

Click here to see if your h ome was in the affected service area.

Haga clic aquí para saber si su hogar ha sido afectado.

Click here for answers to Frequently Asked Questions. 

Haga clic aquí para obtener preguntas y respuestas frecuentes.

Click here for the Tier 2 Public Notice. 

Haga clic aquí para obtener el aviso público de nivel 2. 

Click here for the public notice.

Haga clic aquí para obtener el aviso público. 

Water quality overview

Potable water supplied by the Water Authority to its member agencies comes from three primary sources: the Claude "Bud" Lewis Carlsbad Desalination Plant, the Robert A. Skinner Water Treatment Plant in Riverside County -- owned and operated by the Metropolitan Water District of Southern California -- and the Twin Oaks Valley Water Treatment Plant north of San Marcos.

Here are the 2019 test results for each facility:

In addition to the Water Authority, other agencies that own and operate treatment plants within the county include:

Whether the water is treated by MWD, the Water Authority, or a local agency, all treated water served in San Diego County meets or exceeds rigorous state and federal water quality standards.

Additional Information:

For additional information on fluoridation, click here.

For additional information on lead testing, click here.

To learn more about the water treatment process, click here

To learn more about the Twin Oaks Valley Water Treatment Plant, click here

Other Resources:

Metropolitan Water District: water quality

California State Water Resources Control Board - Division of Drinking Water