Water Quality

Sonoma Water provides quality drinking water to nine cities and water districts in portions of Sonoma and Marin counties. Sonoma Water ensures its drinking water meets all state and federal water quality requirements by performing daily, weekly and monthly tests. 

The U.S. Environmental Protection Agency requires every community water supplier to provide a Consumer Confidence Report to its customers. Sonoma Water provides this report, also known as an Annual Drinking Water Quality Report to our water contractors. Information in this report includes:

  • A summary of the risks of contamination of the local drinking water source.
  • The regulated contaminants found in local drinking water.
  • The potential health effects of any contaminant detected in violation of an EPA health standard. 
  • An accounting of the water system’s actions to restore safe drinking water.
  • An educational statement for vulnerable populations about avoiding Cryptosporidium.
  • Educational information on lead, nitrates, and/or arsenic, in areas where these contaminants may be a concern.

In addition to Sonoma Water’s extensive water quality tests, the cities and water districts that contract to receive this water supply also perform individual water quality sampling and tests. Below are the links to each of the cities’ and water districts’ water quality web pages to learn more about individual testing and results:

As of March 2023, Maximum Contaminant Levels (MCLs) for PFAS in California have not yet been established. The current Consumer Confidence Report Detection Levels for PFAS compounds is 0.040 ug/L (ppb) or 40 ng/L (ppt). Currently, the five individual PFAS compounds that are required to be monitored have the following State Notification and Response Levels:

Chemical Name

Units

Notification 

Response

 

Level

Level

Perfluorooctanoic Acid (PFOA)

µg/L

0.0051

0.010

Perfluorooctane sulfonic (PFOS)

µg/L

0.0065

0.040

Perfluorohexane sulfonic Acid  (PFHxS)

µg/L

0.003 

0.020  

Perfluorobutane sulfonic Acid (PFBS)

µg/L

0.5 

Hexafluoropropylene oxide dimer acid (HFPO-DA)  

µg/L

(1)

(1)

(1) Proposed limits being established.

Result Summary: All water sources that Sonoma Water has tested have been below the Consumer Confidence Report Detection Levels.

On March 14, 2023, the EPA announced the proposed National Primary Drinking Water Regulation (NPDWR) for six PFAS to establish legally enforceable Maximum Contaminant Levels (MCLs) in drinking water. PFOA and PFOS as individual contaminants, and PFHxS, PFNA, PFBS, and HFPO-DA (commonly referred to as GenX Chemicals) as a PFAS mixture. EPA is also proposing health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs) for these six PFAS. 

Frequently Asked Questions:

Where does Sonoma Water get its water from?

Sonoma Water produces water from the Russian River that is pumped from wells about 100 feet below the river bed. This system of pumping is called river bank filtration. Six groundwater wells, also known as collectors, pump the water through natural sands and gravels that act as a filtering system. Sonoma Water does not provide surface water taken directly from a river or lake to its customers.

How does Sonoma Water keep its water clean?

Sonoma Water adds chlorine to its water supply to provide residual disinfection throughout its water transmission system. Sonoma Water also adjusts the pH of its water with sodium hydroxide to address the inherent characteristics of Russian River water that tend to corrode copper plumbing. The quality of drinking water is generally considered in two ways: the presence of contaminants that might cause adverse health effects, and properties of water that affect aesthetics. Contaminants that may cause adverse health effects include inorganic and organic chemicals, and microbiological contaminants. The aesthetic qualities of drinking water include characteristics that make the water unpalatable or bothersome to customers. Examples are hardness, taste, odor, color, temperature and the tendency to discolor plumbing fixtures.

Does Sonoma Water’s transmission system include lead pipes?

No. Sonoma Water's wholesale water transmission system is constructed with underground pipes that are made of concrete lined steel. Contact your local water supplier to learn more about their retail distribution system (see above links).

Why does Sonoma Water adjust the water’s pH?

Excessively high and low pHs can be detrimental for the use of water. High pH causes a bitter taste, water pipes and water-using appliances become corroded or encrusted with deposits, and it depresses the effectiveness of the disinfection of chlorine thereby causing the need for additional chlorine when pH is high. Low pH water can corrode or dissolve metals and other substances. Sonoma Water monitors the level of pH in its water system on a daily basis. The pH level within the water system must achieve an average daily range of 8.2 to 8.6 for 95 percent of all daily average values. To adjust the level of pH Sonoma Water uses Sodium Hydroxide (NaOH), also known simply as caustic soda. Sodium Hydroxide is the most widely used alkaline neutralizing chemical in use in industry today as it is easy to handle and very effective for the neutralization of strong or weak acids. More information on pH is available here.

How old is the water transmission system?

Sonoma Water’s water transmission system varies in age, but elements of it are up to 50 years old. Constant monitoring and water quality testing ensures the pipes are in functional order and ongoing maintenance work is conducted to evaluate and repair leaks or damage before they occur. This type of proactive maintenance work not only reduces health risks associated with leaks but also reduces costs by fixing an issue before it becomes an emergency.

Who monitors Sonoma Water’s water quality reports?

Sonoma Water operates under a water supply permit issued by the State Water Resources Control Board's Division of Drinking Water. This permit requires Sonoma Water to operate and maintain its water supply system in compliance with state water law. This permit includes water quality monitoring requirements and various other conditions and criteria. Sonoma Water consistently meets state and national standards for drinking water quality.

Does Sonoma Water add fluoride to its water?

No. Sonoma Water does not add fluoride. 



Water Quality for Private Wells

The County of Sonoma offers water testing for private wells. Call 707-565-4711 or visit the following websites:

Water Quality Resources: