Water Quality

Local Water Supply

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. 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 2015 Urban Water Management Plan.

Palo Alto Water Quality

The City of Palo Alto Utilities (CPAU) and our water supplier, the San Francisco Public Utilities Commission (SFPUC), 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.

Why drink bottled water when your Palo Alto tap water quality is so great?

Annual Water Quality Report

Your water has a variety of physical, chemical and biological elements that are described in more detail in our annual water quality report. The report is distributed to our utility customers each June for the prior calendar year. Past annual reports are provided below on this webpage.

Current Water Blend Change from SFPUC

SFPUC Blend Change Notice for October 4 and October 11

To conduct maintenance activities on the Hetch Hetchy supply, its flow rate will be reduced to 105 mgd on 10/4/16, and the Sunol Valley Water Treatment Plant (SVWTP) and the Harry Tracy Treatment Plant (HTWTP) rates will be increased to about 40 mgd and 65 mgd, respectively.

On 10/11/16, after completion of the maintenance activities, the Hetch Hetchy rate will be increased to 185 mgd and the HTWTP rate will be lowered to 35 mgd. SVWTP will be put on standby.

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 10-3-16

As of 10-4-16

As of 10-11-16

HH Flow (MGD)












Total Chlorine Residual (mg/L)




Free Ammonia-N (mg/L)








Turbidity (NTU)




Conductivity (uS/cm)




Hardness (mg/L)




Alkalinity (mg/L)




TOC (mg/L)




Water Distribution System Flushing

City staff need to periodically flush water mains and hydrants with fresh water to prevent the water quality from degrading. By doing this, we ensure water is clean and safe to drink, in accordance with State and local guidelines for water quality standards. We post signs at each site to let people know that this is being done. Right now, City staff are flushing water mains in areas of the City 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 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.

Highly Sensitive Customers

Since occasional minor fluctuations in water quality do occur, people with high-sensitivity to water quality issues (e.g. those with compromised immune systems) should consult with their health care provider to determine in general if they should be 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.


Get the facts
 about fluoride in drinking water. Read more from the Centers for Disease Control, American Dental Association, Environmental Protection Agency, and DrinkTap.org. You also read more at theSFPUC fluoridation page.

Chromium 6

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 water supplies we receive from the SFPUC fully comply with the new California Chromium 6 MCL standard finalized in July 2014. Click here for the latest SFPUC report on Chromium 6. Read more from the American Water Works Association on this topic. For detailed information about your water in Palo Alto, visit our water quality report. 


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. 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.

Recent Water Quality Events

March 3, 2015 - Water Quality Event:
  Due to an operational error in the San Francisco Regional Water System, the San Francisco Public Utilities Commission (SFPUC) failed to adequately filter some of its drinking water for a brief period of time on Tuesday, March 3, 2015. This is not, and was not, an emergency. The water mixed with disinfected and filtered water and was well within safety guidelines for drinking water standards according to Palo Alto’s monitoring system results. However, we are required to notify customers of the incident. If this had been an emergency, you would have been notified immediately.
  • All SFPUC affected customers received information after-the-fact in the interest of disclosure and transparency. We want our customers to know what happened and that SFPUC is conducting a thorough investigation to understand and prevent any activities that might lead to a future occurrence.
  • Read a copy of the letter that was mailed to affected customers in Palo Alto.
  • Translated in Spanish.
  • Translated in Chinese.
  • Visit the SFPUC website for more information about the March 4 water delivery incident.
  • Frequently Asked Questions about this incident.

If you have questions about this event, you may contact SFPUC at 
tjue@sfwater.org or 415-290-0163. Additionally, Palo Alto Water Quality staff are available at John.Reinert@CityofPaloAlto.org or (650) 496-6967.

Read more on Palo Alto's Water

SFPUC Hetch Hetchy System Operations

  • Watch a presentation about the SFPUC Water System Improvement Project.
  • View a reference map of the SFPUC Hetch Hetchy System.

Previous Palo Alto Annual Water Quality Reports

  • 2014 Annual Water Quality Report. Also available in Spanish and Mandarin.
  • 2013 Annual Water Quality Report. Also available in Spanish and Mandarin.
  • 2012 Annual Water Quality Report.
  • 2011 Annual Water Quality Report.
  • 2010 Annual Water Quality Report.
  • 2009 Annual Water Quality Report.
  • 2008 Annual Water Quality Report.

Last Updated: Oct 11, 2016