Water Resources

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 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. Click here to view minor edits to the Urban Water Management Plan.

Water Quality & Annual Consumer Confidence Report

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 Consumer Confidence Report which informs customers about the City's water quality. This report is also available in Mandarin and Spanish. Past annual reports are provided below on this webpage.

If you would like a copy of the report mailed to you, please email us at UtilitiesCommunications@cityofpaloalto.org or call (650) 329-2479 to submit a request. Click here for the 2016 Public Health Goals Report. Read about tap water quality versus bottled water.

Current Water Blend Change from SFPUC

The San Francisco Public Utilities Commission (SFPUC) is currently blending water from the Hetch Hetchy reservoir with water from surface reservoirs along the Peninsula and in the East Bay. This blend change is necessary to accommodate operations and maintenance on the San Francisco Regional Water System.

Read more about the SFPUC water distribution system, including a map of Alameda and Peninsula water sources: https://sfwater.org/index.aspx?page=355

Operational changes of the Hetch Hetchy supply will begin on Wednesday, May 17. Palo Alto customers may notice a change in water quality aesthetics of taste or odor within 12 to 48 hours of this operational change.

Potential Change in Taste, Color or Odor

As with any water source blend change, there is a possibility that turbidity could stir up material in the pipes. SFPUC and City staff test the water every day to ensure it meets safe standards for drinking water. 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 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. You will be notified of further changes.

Parameter As of 11-9-17 As of 11-10-17
HH Flow (MGD) 0 130
HTWTP Flow (MGD) 97 80
SVWTP Flow (MGD) 113 0
Total Chlorine Residual (mg/L) 2.8 2.8
Free Ammonia-N (mg/L) 0.08 0.04
pH 8.9 9.6
Turbidity (NTU) 0.17 0.3
Conductivity (uS/cm) 303 44
Hardness (mg/L) 94 8
Alkalinity (mg/L) 91 11
TOC (mg/L) 2.5 1.2

Highly Sensitive Customers

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.


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 City's lead or other water quality testing procedures, please contact our Water Transmission Staff at (650) 496-6967.


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 the SFPUC 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.

Read more on Palo Alto's Water

Palo Alto’s long-term water supply forecast, water demand and conservation programs in the 2015 Urban Water Management Plan. Click here to view minor edits to the Urban Water Management Plan.

  • Stay Informed! Get updates on breaking news about any water disruptions or quality issues by following us on Twitter @PAUtilities
  • Report a substantial leak, break or other emergency by calling (650) 329-2579
  • Report over-watering or other water waste by emailing drought@cityofpaloalto.org or by calling (650) 496-6968.
  • Read more about water rates & supplies.
  • Backflow prevention surveys--get the full scoop about what is going on and why here.
  • Palo Alto's Recycled Water Plan

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

Last Updated: Nov 7, 2017