Water Quality

Ensuring safe, clean water

Every year, the district conducts more than 115,000 water quality and process control tests to ensure your water is safe to drink. This includes ongoing process control testing at our treatment plants as well as laboratory testing of our water samples. When it comes to health and safety, your drinking water is required to meet or exceed all state and federal drinking water standards.

For assistance with your water quality questions or concerns, please contact us at 415.945.1550 or WaterQuality@marinwater.org.

April 22, 2026 – Seasonal notice to customers regarding water taste and odor

Occasionally, during the warmer months, some customers experience a different taste or odor in their drinking water. Some describe the water as tasting and smelling earthy or musty. This temporary change is caused by naturally occurring compounds produced by algae growth which occurs in some areas of our reservoirs during sunnier times of the year.

These slight changes, which are common in lake/reservoir water, do not affect the safety of your water. Your water continues to be properly treated and meets or exceeds all state and federal requirements.

For those who are more sensitive to taste and odor changes, chilling the water during these periods will help reduce the temporary change in taste or smell of your water.

For questions or for more information, contact us by emailing waterquality@marinwater.org or by calling 415.945.1550.

Topics in the news

Marin Water addresses items of current interest, including recent guidance, external studies and/or timely issues circulating in the news.

Fluoridation of Drinking Water

Oct. 1, 2024

Marin Water serves more than 190,000 community members in central and southern Marin County and is committed to providing safe drinking water for our customers.

A recent federal district court ruling found that the US Environmental Protection Agency should reexamine the allowable levels of fluoride in drinking water. This may have raised questions or concerns around the safety of community water fluoridation. Fluoride, one of the most plentiful elements on earth, often occurs naturally in water supplies. Water fluoridation is the process of adding small amounts of fluoride to a water supply to achieve the fluoride level recommended by the California State Water Resources Control Board Division of Drinking Water (DDW) to prevent tooth decay.

Marin Water has been adding fluoride to its drinking water since a voter initiative in support of this practice was passed in 1973 and re-confirmed in 1978. Fluoride is added at our water treatment plants and is monitored continuously to ensure that the optimum level of fluoride is maintained in our drinking water.

California’s fluoridated drinking water act, Assembly Bill 733, became law in 1995, requiring water systems with 10,000 or more service connections, with some exceptions, to fluoridate their water supply. Additional information on fluoridation of drinking water can be found on the California State Water Resources Control Board website.

Marin Water monitors all drinking water standards and requirements closely and will provide updates as there is new information to share.

Chloronitramide in Drinking Water

Nov. 25, 2024

Researchers at the University of Arkansas recently reported that they had identified a compound called chloronitramide anion, a disinfection byproduct that is present in drinking water treated with chloramines. Marin Water uses chloramines in accordance with drinking water regulations, and while this discovery may be cause for concern, scientists are not certain that chloronitramide is harmful at the quantities present in drinking water. Neither the State of California nor the Federal Environmental Protection Agency have released a statement or any new directives concerning chloronitramide. Customers who are concerned and want to take action may consider using activated carbon filters typically found in modern refrigerators or a pitcher-style activated carbon filter, such as Brita. Marin Water will be following this topic closely and will provide updates as more information is developed.