Palo Alto’s water comes from the San Francisco Public Utilities Commission (SFPUC). This high quality water supply consists almost entirely of Sierra Nevada snowmelt delivered through the Hetch Hetchy water distribution system.
Precipitation levels can vary greatly within any given year. Even though we may experience periods of wet weather, a warm dry spell can affect water supplies later in the year. These climate conditions, along with our limited long-term water supplies, mean it is in our best interest to use water as efficiently as possible, regardless of drought conditions. Read the City of Palo Alto's 2015 Urban Water Management Plan.
Current Water Blend Change from SFPUC
The San Francisco Public Utilities Commission (SFPUC) is completing infrastructure improvement work on the Mountain Tunnel pipeline facility that delivers water to its wholesale customers from the Hetch Hetchy Reservoir. In order to accommodate this work over the past few months, SFPUC had shut down the water supply from Hetch Hetchy and delivered water from local surface reservoirs to wholesale customers, including Palo Alto. SFPUC plans to bring the Hetch Hetchy water supply back online this weekend (March 11-12).
As with any water source blend change, there is a possibility that turbidity could stir up material in the pipes. While SFPUC does not anticipate any changes in water quality or aesthetics of taste, color or odor to our water, there is always the possibility that customers may notice a slight change in the water coming from their taps.
SFPUC and City staff test the water every day to ensure it meets safe standards for drinking water, and we will continue to work with SFPUC to deliver timely information about any changes in water quality aesthetics. Please contact our Water Transmission staff at (650) 496-6967 if you have any questions or concerns. You can also email us at UtilitiesCommunications@cityofpaloalto.org
Water Quality Parameters
The Hetch Hetchy (HH) supply is being restored to service after completion of the Mountain Tunnel inspection. The lower portions of the HH Aqueduct (specifically San Joaquin Pipeline #2 and the Coast Range Tunnel) will be flushed from March 10 to March 12. Deliveries of HH water are tentatively planned to resume on Sunday, March 12. The Sunol Valley Water Treatment Plant (SVWTP) and the Harry Tracy Water Treatment Plant (HTWTP) will each remain in service at reduced flow rates.
The following table compares water quality parameters at Irvington Portal. This data is based on the most recent sampling results and represents an estimate of how the blend parameters will change.
As of 3-11-17
As of 3-12-17
HH Flow (MGD)
HTWTP Flow (MGD)
SVWTP Flow (MGD)
Total Chlorine Residual (mg/L)
Free Ammonia-N (mg/L)
The Hetch Hetchy (HH) supply is being restored to service after completion of the Mountain Tunnel inspection. The lower portions of the HH Aqueduct (specifically San Joaquin Pipeline #2 and the Coast Range Tunnel) will be flushed from March 10 to March 12. Deliveries of HH water are tentatively planned to resume on Sunday, March 12. The Sunol Valley Water Treatment Plant (SVWTP) and the Harry Tracy Water Treatment Plant (HTWTP) will each remain in service at reduced flow rates. The following table compares water quality parameters at Irvington Portal. This data is based on the most recent sampling results and represents an estimate of how the blend parameters will change.
Palo Alto Water Quality
The City of Palo Alto Utilities and our water supplier are required by law to adhere to strict health and safety standards for potable drinking water. Every year we publish an annual water quality report, which informs customers about the City's water quality. General questions or concerns? Call us at (650) 329-2161 to report issues or request information.
Your water has a variety of physical, chemical and biological elements that are described in more detail in our annual water quality report. This report is updated every year and made available to our utility customers. Past annual reports are provided below on this webpage.
Since occasional minor fluctuations in water quality can occur, we encourage people who may be vulnerable to drinking water contaminants to seek advice from their health care provider, who may recommend taking precautionary measures such as adding filtration devices. Please contact our Water Transmission division at (650) 496-6967 with any questions about water quality or blend changes.
Water Distribution System Flushing
City staff need to periodically flush water mains and hydrants with fresh water to prevent the water quality from degrading. This is more frequently needed in areas where a cul-de-sac or end-of-the-line piping tend to accumulate vegetation, algae or sediment. Flushing is necessary to keep debris out of customers' service line. We post signs at each site to let people know that this is being done.
We monitor our water quality every day to ensure that it meets all State and Federal guidelines for drinking water quality standards. If a customer experiences discoloration or sediment in water coming from the tap, they should flush the cold (not hot) water for a minute or more until the water clears.
Chromium is an abundant element in the Earth’s crust, found naturally in rocks, plants, soil and volcanic dust, humans and animals. One form, hexavalent chromium, is widely found in waters, including source waters for drinking water, typically at VERY low concentration levels. Chromium 6 is not a concern in Palo Alto.
The City of Palo Alto takes its responsibility to protect customers from lead exposure very seriously. Palo Alto Utilities does not have lead services or other equipment in our system, though we still perform sampling to ensure clean, safe drinking water quality. Currently, we are working with Palo Alto Schools on plans to test lead levels in any requested K-12 school site. The City of Palo Alto’s lead sampling technique uses best practices for accurate water quality testing. If you have questions about the CPAU lead or other water quality testing procedures, please contact our Water Transmission Staff at (650) 496-6967.