Is San Jose, CA Tap Water Safe to Drink?

Where Does San Jose Get Its Water?

San Jose, CA draws its drinking water from a mix of local groundwater wells and imported surface water. The city is served by five water systems, with San Jose Water and the City of San Jose's own utility systems being the primary providers for most residents. Water imported from regional sources enters the system through interconnections with Valley Water (formerly Santa Clara Valley Water District) and the San Francisco Public Utilities Commission.

The Montevina Water Treatment Plant is the main recognizable surface water treatment facility serving part of the city. Groundwater comes from several wellfields, including the Edenvale Wellfield and the Evergreen Wellfield, along with individual wells distributed across the service area. These groundwater sources are treated at multiple chlorination stations before reaching taps.

Great Oaks Water Company serves some San Jose neighborhoods independently, drawing on its own local groundwater. A small number of customers are served by HGST Inc., which operates its own system. Across all providers, the underlying aquifer and imported Bay Area surface water are the backbone of the local supply.

How Is San Jose Tap Water Treated?

Water treatment in San Jose involves several steps depending on the source. Surface water goes through conventional treatment processes including coagulation and filtration before disinfection. The Montevina Water Treatment Plant applies more advanced treatment, and the system as a whole uses processes including biological treatment, powdered activated carbon, and other methods to reduce contaminants before water enters distribution.

Disinfection across San Jose's water systems uses free chlorine and chloramines, as well as ozone at certain points in the treatment train. Ozone is a powerful oxidant that helps break down organic compounds, while chloramines provide a longer-lasting disinfectant residual through the pipes to your tap. UV treatment is also used at some facilities as an additional safeguard against pathogens.

Groundwater wells are typically treated at individual chlorination stations before the water enters the distribution system. This decentralized approach means groundwater from different parts of the city goes through its own treatment step. The result is a layered system designed to meet federal and state drinking water standards.

What's in San Jose Tap Water?

The most notable finding from recent EPA testing is PFTrDA, a type of PFAS (per- and polyfluoroalkyl substance), detected at a peak of 0.007 µg/L. That peak value equals EPA's health reference level for this compound, and detections were found across a large number of ZIP codes in the city, with 16 ZIPs showing levels at or above the guideline. PFAS are a broad family of industrial chemicals that persist in the environment and in the body.

Lithium was detected in San Jose tap water at levels up to 15.4 µg/L. EPA has a non-regulatory health reference level of 10 µg/L for lithium in drinking water, and the peak here exceeds that threshold. Lithium is a naturally occurring element found in some groundwater and is not subject to an enforceable federal maximum contaminant level. Several other PFAS compounds, including 8:2 FTS, PFBA, and 6:2 FTS, were detected at low levels but did not exceed any applicable guidelines.

PFAS compounds in drinking water typically trace back to industrial uses, firefighting foams used at airports and military sites, and certain consumer products. Lithium in groundwater is generally a natural geologic occurrence, though concentrations can vary by aquifer. The presence of multiple PFAS compounds alongside lithium reflects both the regional industrial history and the local geology of the Santa Clara Valley.

Health Risk Profile for San Jose

For PFTrDA, EPA has set a health reference level of 0.007 µg/L. San Jose's peak detected value matched that threshold exactly. This is a non-regulatory benchmark, not an enforceable federal drinking water limit, meaning utilities are not in legal violation. For lithium, the EPA health reference level is 10 µg/L, and the peak value here was 15.4 µg/L, also above a non-regulatory screening benchmark with no enforceable federal maximum contaminant level.

Infants, pregnant individuals, and people who are immunocompromised may face greater risk from some of these contaminants at elevated levels. PFAS compounds have been linked in research to effects on immune function, thyroid health, and fetal development. Lithium at elevated levels is a concern especially for infants and during pregnancy. If you fall into one of these groups, consulting a healthcare provider about your tap water is a reasonable step.

For PFAS, a filter certified to NSF/ANSI 58 (reverse osmosis) or NSF/ANSI P473 (specifically tested for PFAS) is the most effective option. NSF/ANSI is an independent third-party certification program, so look for that label on the box or the manufacturer's product page. A certified pitcher, under-sink, or whole-house filter can substantially reduce PFAS levels at the point you use water for drinking and cooking.

The science on low-level PFAS and lithium exposure is still developing, and EPA's health reference levels are precautionary benchmarks rather than firm thresholds between safe and unsafe. For most healthy adults, short-term exposure at the levels found in San Jose is unlikely to cause acute harm. The concern is primarily with long-term, cumulative exposure, which is why filtering makes sense if you drink tap water daily.