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Ensuring safe, reliable water
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How we clean your water

Rinconada Water Treatment Plant, Penitencia Water Treatment Plant, Silicon Valley Advanced Water Purification Center, and Santa Teresa Water Treatment Plant (Left to Right)

Before we can drink water brought into the county through canals and pipelines from the Sacramento-San Joaquin Delta or collected in local reservoirs, the water must undergo an extensive treatment process. Valley Water operates three water treatment plants that clean and disinfect imported water and/or water captured in four of our local reservoirs. 

The three water treatment plants, Rinconada, Santa Teresa and Penitencia, are located in the foothills around the Santa Clara Valley and rely on gravity to deliver the treated water to retailers (such as San Jose Water Company). These three plants can produce as much as 220 million gallons of drinking water daily.

Following upgrades at the Santa Teresa and Penitencia plants in 2006, ozone is used as the primary disinfectant at these two water treatment plants. Ozone disinfection is more effective than chlorine at inactivating microbial contaminants like Giardia and Cryptosporidium. Also, using ozone in place of chlorine can significantly reduce the formation of trihalomethanes (THMs), a byproduct of chlorine disinfection that may be harmful at high levels. While Valley Water has not detected high levels of THMs in our drinking water, ozone significantly lowers the potential forming of THMs.

Another significant benefit of ozone is that it removes unpleasant tastes and odors often caused by seasonal algal blooms in our source waters. Ozone has enhanced our ability to address this and generally improves the taste of our drinking water.

Major upgrades are currently underway at Rinconada, our oldest water treatment plant. These upgrades, anticipated to be completed in 2029, will replace or upgrade all major plant components, including the addition of ozone, and increase Rinconada’s treatment capacity from 80 to 100 million gallons of water daily.

While surface water, whether from local reservoirs or imported through pipelines, must be treated before it is drinkable, water pumped from wells is naturally filtered through soils and rock formations; particles and pathogens are removed as the water percolates down to underground aquifers. Water retailers in the Santa Clara Valley that use wells to augment their drinking water supplies (received from our treatment plants) may provide disinfection to the well water for additional health protection.

The San José-Santa Clara Regional Wastewater Facility treats most of the wastewater in the county. Some water from the plant receives advanced treatment from the Silicon Valley Advanced Water Purification Center and is recycled by South Bay Water Recycling.