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For more information about water quality, or for any questions relating to your drinking water, please contact (805) 781-7215

Water Quality

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Water Quality/Consumer Confidence Reports

We are once again proud to present our annual water quality report covering all testing performed between January 1, and December 31, 2023. Over the years we have dedicated ourselves to producing drinking water that meets all state and federal standards. We continually strive to adopt new methods for delivering the best quality drinking water to you. As new challenges to drinking water safety emerge, we remain vigilant in meeting the goals of source water protection, water conservation, and community education while continuing to serve the needs of all our water users.

Read our 2023 Annual Water Quality Report

Please remember that we are always available to assist you should you ever have any questions or concerns about your water.

Drinking Water Fluoridation

A blue icon of a glass of water with a droplet dropping from above The City adds fluoride to the treated water produced by the water treatment plant to help prevent dental caries in consumers. State regulations require the fluoride levels in the treated water be maintained within a range of 0.6 - 1.2 ppm with an optimum dose of 0.7 ppm. For more information on our monitoring, please see the City's current Consumer Confidence Report (CCR). Information about fluoridation, oral health, and current issues is available from the California State Water Resources Control Board .

Important Health Information

A blue icon of a heart with a plus sign to signify health Some people may be more vulnerable to contaminations in drinking water than the general population. Immunocompromised persons such as persons with cancer undergoing chemotherapy, persons who have undergone organ transplants, people with HIV/AIDS or other immune system disorders, some elderly, and infants may be particularly at risk from infections. These people should seek advice about drinking water from their health care providers. The U.S. EPA/CDC (Centers for Disease Control and Prevention) guidelines on appropriate means to lessen the risk of infection by Cryptosporidium and other microbial contaminants are available from the Safe Water Drinking Hotline at (800) 426-4791 or water.epa.gov/drink/hotline.

Source Water Assessment

A blue icon of a water reservoir Assessments of the drinking water sources for the City of San Luis Obispo have been conducted and include Salinas Reservoir, Whale Rock Reservoir, and Nacimiento Reservoir. These water sources are considered most vulnerable to the following activities not associated with any detected contaminants: grazing, managed forests, recreational areas, septic systems, sewer collection systems, gas stations and historic mining activities. A copy of the complete assessment is available from the SWRCB Division of Drinking Water (1180 Eugenia Place, Suite 200, Carpinteria, California, 93013) or the City of San Luis Obispo (879 Morro Street, San Luis Obispo, California, 93401). A summary of the assessment can also be requested by contacting (805) 781-7215.

Lead in Home Plumbing

A blue icon of a plumbing pipe If present, elevated levels of lead can cause serious health problems, especially for pregnant women and young children. Lead in drinking water is primarily from materials and components associated with service lines and home plumbing. The City is responsible for providing high-quality drinking water but cannot control the variety of materials used in home plumbing components.

If you are unsure if your home plumbing uses materials containing lead, you can reduce the risk for lead exposure by flushing your tap for one to two minutes before using water for drinking and cooking. Flushing your line is only needed if your water has been unused for several hours. If you are concerned about lead in your water, you may wish to have your water tested. Information on lead in drinking water, testing methods, and steps you can take to minimize exposure is available from the Safe Water Drinking Hotline or at www.epa.gov/safewater/lead.

Chemicals Not Found in SLO’s Drinking Water Supply

PFAS (per- and polyfluoroalkyl substances)

Quick Facts About PFAS in the City of SLO

The City’s drinking water is not currently impacted by PFAS, based on recent water quality sampling. This is largely due to the City’s use of surface water supplies that are in rural locations where PFAS is not commonly found.
The city will continue to monitor drinking water and wastewater for PFAS, as required by EPA and State of California regulations.
The City does not use groundwater as a drinking water supply, and all the surface water samples have been free of PFAS.
As the City reestablishes its use of groundwater, treatment systems will be designed to remove PFAS and staff will conduct ongoing PFAS sampling to ensure that PFAS is not delivered into the City’s drinking water system through the use of groundwater.
The City’s Fire Department does not use firefighting foam that contains PFAS.

Here's what you need to know about PFAS

PFAS are chemicals that have been used in various industries worldwide since the 1940s. In the US, they are still used in products, but there's a growing movement to regulate or stop their use. PFAS can be found in things like non-stick cookware, some waterproof clothes, household items, and certain firefighting foams. Even though the City's Fire Department hasn't been required to, they've chosen not to use foams with PFAS to avoid potential environmental harm.

PFAS have spread in water, soil, and air globally due to their widespread use. Recent studies suggest that exposure to certain levels of PFAS can be harmful to human health.

PFAS in Drinking Water

The Environmental Protection Agency (EPA) and State of California are working on setting regulations that restrict the concentrations of PFAS that can be in drinking water. Sampling of drinking water supplies at the City’s water treatment plant, concluded that there is no PFAS present in the City’s drinking water supplies.

As the city plans to reinitiate its use of groundwater, the Utilities Department will test and monitor groundwater for PFAS and will design appropriate treatment systems to remove PFAS from groundwater prior to delivery into the City’s drinking water system.

PFAS in Wastewater

In 2020 and 2021, the City’s Water Resource Recovery Facility (WRRF), where the City treats its wastewater, completed four rounds of testing for PFAS. This testing was part of a statewide study covering all large wastewater plants in California. Most of the test results showed no PFAS, except for one sample that had a trace amount that was too small to reliably measure with current methods.

Because PFAS are found in many everyday items, they can end up in wastewater when we shower, wash dishes, or do laundry. In our city, where PFAS is not in the drinking water, it's likely that any PFAS present in wastewater is coming from personal use of PFAS-containing products. As rules for PFAS in drinking water are formalized, similar rules for wastewater are expected to follow.

PCE (Tetrachloroethylene)

Quick Facts About PCE in the City of SLO

The City’s drinking water supply does not contain PCE.
As the City expands its groundwater program, any PCE found in groundwater supplies will be appropriately treated before the water is delivered as a drinking water source.
Right now, the City does not use groundwater as a drinking water supply, and all surface water supplies are free from PCE.
The City will continue to sample drinking water for PCE, as required by EPA and California regulations.

Here's what you need to know about PCE

The City’s drinking water currently comes from Whale Rock Reservoir, Salinas Reservoir, and Nacimiento Lake. However, the City has been interested in diversifying its water supply by adding groundwater as an additional water supply. Several years ago, a plume of PCE was detected in specific areas within the groundwater basin after groundwater sampling. PCE, or tetrachloroethylene, is a chemical that is believed to have been utilized in past dry cleaning and industrial activities that have since ceased operation within the City.

Despite the suspected source of the PCE contamination being eliminated, PCE still exists in specific areas of the City’s groundwater basin and needs to be cleaned up before groundwater can be used as a drinking water supply. The City recently received a $6.6 million grant to assist with identifying where PCE is concentrated in the groundwater basin and to aid in installing groundwater wells and treatment systems to pump and treat contaminated water. This project will result in PCE being treated and removed from the groundwater basin, helping eliminate the decades-old contaminant, and helping ensure that the City has safe groundwater to supplement its surface water supplies.