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Updated: 06.27.23

Is Pleasanton's Water Safe?

The City of Pleasanton delivers safe, reliable drinking water to 22,000 customers by operating in compliance with all state and federal guidelines and regulatory requirements. 


About PFAS

What are PFAS?

Per- and polyfluoroalkyl substances (PFAS) are a large group of human-made chemicals that do not occur naturally in the environment. They have been used since the 1940’s in making commercial products such as carpets, clothing, food packaging, and cookware due to their waterproof, stain-resistant, and nonstick properties. They have also been used in fire-retarding foam and various industrial processes.

Perfluorooctane-sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are currently the most well-known and studied types of PFAS. PFOS and PFOA were mostly phased out of production between 2000 and 2006, but traces of both are still found in the blood of nearly all people tested in recent national monitoring surveys.

How are people exposed to PFAS?

PFAS can be introduced into the body through eating or drinking contaminated food or liquid (including water) and inhaling or touching products with packaging treated with them such as carpeting or clothing. The most common way of being exposed to PFAS is by eating contaminated food.

How does PFAS get into drinking water?

PFAS can contaminate drinking water supplies when products containing them are used or spilled on the ground and PFAS migrates into groundwater. Once in groundwater the substances can travel large distances and can contaminate drinking water wells. PFAS can similarly contaminate drinking water by entering lakes and rivers that are connected to drinking water supplies. The major sources of PFAS contamination in drinking water are believed to be from fire training/fire response sites, industrial sites, landfills, and wastewater treatment plants/biosolid facilities.

What are the health effects related to PFAS exposure?

The industry’s understanding and ability to detect PFAS in the environment has evolved and we are now able to measure extremely small amounts (parts per trillion in water) of a number of PFAS and newer studies suggest that long-term exposure to PFAS in this range might affect the most vulnerable members of the population.

Although more research is needed, scientific studies indicate that exposure to PFAS can lead to significant health effects, especially in pregnant women or women likely to become pregnant and in children. Studies also show that PFAS may affect growth, learning, and behavior of babies and older children, affect the immune system, increase cholesterol levels, and increase cancer risk.


PFAS regulation

How is PFAS in drinking water regulated?

Over the past several years, the science on PFAS and its impacts to the environment and public health have prompted regulatory consideration. In California, there are both state and federal regulations water suppliers must abide by.

Federal Guidelines

The U.S. Environmental Protection Agency (EPA) has issued health advisories for certain PFAS. These health advisories can be found at the following link: EPA Health Advisories. Additionally, the EPA is in the process of establishing federally enforceable drinking water standards for PFAS nationwide. View the EPA's proposed PFAS regulations here.

State Guidelines

The California State Water Resources Control Board (SWRCB) requires testing on a quarterly basis to identify the extent of contamination of drinking water sources in the state.

The California State Water Resources Control Board (SWRCB) has also issued drinking water advisory levels for certain PFAS as noted in the table below and is pursuing advisory levels for additional PFAS. Additionally, the SWRCB is in the process of establishing enforceable drinking water standards for PFAS.

PFAS in Pleasanton

Where does Pleasanton's drinking water come from?

The City owns and operates its own water distribution system that distributes approximated 4,500 million gallons of treated water a year to 22,000 customers. The City normally purchases approximately 80% of its potable water supply from the Zone 7 Water Agency, while the remaining 20% is supplied by city owned and operated groundwater wells.

Does Pleasanton treat water from its groundwater wells for PFAS?

Currently, the City does not have PFAS treatment facilities for the water that is supplied by our local groundwater wells.

Zone 7 has the ability to blend and dilute water with PFAS and is building a PFAS treatment facility at its Stoneridge Well that should be completed and in operation in late summer 2023.

Where can I find PFAS test results for Pleasanton's water?

A summary of all PFOA and PFOS test results for Pleasanton can be found at the following link: View the most recent PFAS Test Results.

How frequently does Pleasanton test water from groundwater wells?

The state requires water suppliers to test for PFAS quarterly. The Pleasanton City Council recently requested that water from Pleasanton’s groundwater wells be tested monthly to provide more frequent results.

What is the turnaround time to get PFAS test results?

Turnaround time for PFAS test results is about 3 - 4 weeks.

What is the status of Pleasanton's groundwater wells?

Pleasanton currently has three groundwater wells that it operates – wells 5, 6, and 8.

Wells 5 and 6 are still “In Service” with the SWRCB since currently below response levels, but have not been in operation since November 2022 after testing showed PFAS above the notification level, but below the response level. In summer 2023, wells 5 and 6 will be used as needed during peak demand.  

Well 8 was placed in “Standby Service” with the SWRCB in June 2019 due to PFOS concentrations being above the response level at that time. The well has not operated since June 2019.

Does Pleasanton test Zone 7's water when it comes into our system?

The City does not test Zone 7’s water when it gets to our distribution system. Zone 7 is required to do the same quarterly testing and reporting to the State and meet the same notification level and response level requirements.

Is Zone 7's water safe?

Zone 7's water is safe. No PFAS have been detected in treated surface water supplies which is typically the majority of the total water delivered to its customers.

There have been detections in some of the groundwater wells. In the instances where these contaminants have been sampled above response levels in Zone 7 wells, Zone 7 has taken steps to treat the contaminants to concentrations below the response level in all water delivered to customers.

What is the status of PFAS at Zone 7?

A summary of PFAS test results for Zone 7 can be found at the following link: PFAS Test Results.

Zone 7 has been blending groundwater wells and/or treating groundwater at its Mocho Groundwater Demineralization Facility so that all drinking water is below Response Levels before being delivered to Pleasanton’s water distribution system.

Does Zone 7 test and treat its water?

Wells that have tested above the response level and that do not have current treatment options have been temporarily taken out of service while treatment facilities are constructed. Zone 7 is currently constructing water treatment facilities that utilize ion resin exchange to address PFAS at the Chain-of-Lakes and Stoneridge Well sites.


How is Pleasanton addressing PFAS?

Pleasanton is engaged in several projects to address PFAS and our overall water supply and quality. Learn more about these projects here.


Treating for PFAS at home

Can I treat my water for PFAS at home?

Home water treatment can be installed to reduce levels of PFAS. Treatment can be at the point of use (kitchen sink, refrigerator, etc.) or at the point of entry (where treatment occurs for all the water entering your home). The two suggested effective home treatment systems for reducing PFAS are granular activated carbon (GAC) treatment systems and reverse osmosis (RO) treatment systems.

Granular activated carbon treatment system

  • Physical filter cartridge traps contaminant(s) which is then removed and disposed of at the end of its rated lifecycle.
  • A filter must be replaced on a regular schedule (identified by manufacturer).
  • Generally easier to install, lower initial cost, and provides more water flow than reverse osmosis systems.
  • May not effectively treat shorter-chain PFAS (if present) in addition to the longer-chain PFAS such as PFOA and PFOS.

Reverse osmosis treatment system

  • Systems force water through a membrane under pressure, leaving the contaminants at the membrane.
  • Typically requires pre-filtration to be installed to remove any sediment and small particles to maximize the life and effectiveness of the membrane.
  • Membranes and any pre-filtration cartridges must be replaced on a regular schedule (identified by manufacturer).
  • Large volumes of water are wasted in the treatment process.
  • Research has shown potential to effectively reduce shorter-chain PFAS in addition to the longer-chain PFAS such as PFOA and PFOS.

How do I know if my home water treatment is working?

The best way to know if your home treatment system is effective is to make sure that it is tested by an independent third party. The packaging for the filter will typically contain this information. This information can also usually be found on the manufacturer’s web page. Make sure that the filter has been tested using a NFS standardized methodology such as NSF/ANSI Standard 53 Drinking Water Treatment Units

What are the best filters for removing PFAS?

One way to reduce PFAS in your home is to use a water filter rather. But with so many filters on the market, and many marketing claims about eliminating PFAS, it can be hard to know which one is best for your home. The Environmental Working Group has issued a press release regarding tests they conducted on the effectiveness of ten different pitcher filters to remove PFAS from drinking water.


Other water information

Where can I find more information?

Additional information is available at:

For more information, contact the City of Pleasanton Public Works Department by calling 925-931-5500 or by emailing


Reference Documents

Notification to Utility Customers of PFAS/PFOS Webpage Email to Utility Customers November 2019