Contaminant Regulations
The EPA and SWRCB prescribe regulations that limit the amounts of certain contaminants in water provided by public water systems to ensure its safety. U.S. Food and Drug Administration regulations and California law also establish contaminant limits in bottled water to provide protection for public health, though it’s tested less frequently than tap water.
Drinking water, including bottled water, may be expected to contain small amounts of contaminants; their presence doesn’t necessarily indicate that the water poses a health risk.
Naturally Occurring Drinking Water Contaminants
Tap and bottled drinking water sources include rivers, lakes, streams, ponds, reservoirs, springs and wells. Travelling water dissolves naturally occurring minerals and, in some cases radioactive material, potentially picking up substances resulting from animal or human activity.
Naturally occurring source water contaminants may include:
- Microbials (viruses, bacteria): sewage treatment plants, septic systems, agricultural livestock operations or wildlife
- Inorganics (salts, metals): from stormwater runoff, wastewater discharges, oil and gas production, mining, farming or naturally occurring
- Pesticides/herbicides: agriculture, stormwater runoff or landscaping
- Organic chemicals: byproducts of synthetic and volatile organic chemical industrial processes and petroleum production or gas stations, stormwater runoff, agricultural and septic systems
- Radioactive contaminants: naturally occurring or resulting from oil/gas production or mining activities
PFAS and Lithium Monitoring
The purpose of the Unregulated Contaminant Monitoring Rule (UCMR), set by the EPA, is to understand the prevalence and quantity of unregulated contaminants in drinking water systems.
From 2023 to 2025, two turnouts and eighteen groundwater wells were tested for Lithium and 29 Per- and Polyfluorylalkyl Substances (PFAS) for the Fifth Unregulated Contaminant Monitoring Rule (UCMR5). No PFAS compounds or Lithium have been detected at all locations sampled for UCMR5.
Lead
No Santa Clara water sources have exceeded the ACTION LEVEL for lead. Lead levels in your home may be higher than others due to plumbing in your home’s original construction. Elevated lead levels can cause serious health problems, especially for pregnant women and young children.
Lead in drinking water comes from service line and home plumbing components. The City provides high quality drinking water, but cannot control materials used in your home’s plumbing. When water hasn’t been used for several hours, you can minimize potential lead exposure by:
- Flushing your tap for 30 seconds to 2 minutes before using water for drinking or cooking. (Use collected flushing water for cleaning, watering plants or running your garbage disposal.)
- Using only cold water for drinking and cooking.
Concerned about lead in your water? Visit the EPA lead webpage
An initial lead service line inventory was completed in 2024 where more than 2,000 service lines were inspected. No lead services were found during inspections. A summary of the inventory can be found at SantaClaraCA.gov/WaterServiceLineInventory
Nitrates in Groundwater Resources
Nitrate levels above 10 ppm in drinking water can interfere with the capacity of blood to carry oxygen in infants under six months old, pregnant women or those with specific enzyme deficiencies, resulting in serious illness. If you are pregnant or caring for an infant, consult your health care provider.
Tier 3 Notice from SFPUC
The SFPUC notified the City of a monitoring violation, as is required within one year of discovery. Because of equipment failure, the San Francisco Regional Water System (SFRWS) operated by the SFPUC, did not monitor for recycled filter backwash water turbidity at its Sunol Valley Water Treatment Plant (SVWTP) from June 23 to July 2, 2025. It was corrected July 3, 2025, once it became apparent to plant staff. There was no emergency or impact to SFPUC's water quality.
At the SVWTP, treated or “backwash” water washes filters after a completed run cycle. Instead of wasting backwash water, it's treated, recycled and blended with source or lake water; it then goes through the whole treatment process again. Downstream monitoring indicated that SVWTP's effluent (final product) was consistently of very high quality and exceeded all drinking water standards.
The turbidimeter, which monitors turbidity for recycled water, was not operating during the failure period. Since its repair and resumed operation on July 3, 2025, the daily monitoring of recycled filter backwash water turbidity has been uninterrupted. Additional operational and maintenance activities, including staff retraining, were implemented to prevent a recurrence. For more information, please contact the resources listed on the last page of this report.
Hexavalent Chromium
Hexavalent Chromium, also known as Chromium-6, occurs naturally throughout California from the erosion of chromium deposits. It’s used in various applications: paints, dyes, anticorrosion coatings and other industrial uses. As of October 1, 2024, the regulatory standard for Hexavalent Chromium is 10 ppb. Our 20 groundwater wells were tested for Hexavalent Chromium and were all found to be below 10 ppb.
SFPUC Water: Tested for Cryptosporidium & Giardia
Monthly (or more frequent) tests of SFPUC source and treated waters occasionally show very low levels of Cryptosporidium and Giardia in water serving the East Bay, South Bay and San Francisco Peninsula.
Cryptosporidiosis, an intestinal tract disease brought on by a parasitic microbe called Cryptosporidium, transmits through contaminated water, food or direct contact with human or animal waste. Giardia is caused by a different parasitic organism, but also causes symptoms similar to flu. Symptoms usually last about two weeks for those with normal immune systems. Immuno-compromised people, infants, small children and the elderly are at greater risk of developing life-threatening illness.
Guidance from the California Department of Public Health and County health agencies recommend that people with serious immune problems consult their health care providers about preventing Cryptosporidium and Giardia infection. They may choose to bring drinking water to a rolling boil for at least one minute as an extra precaution.
Cryptosporidiosis and Giardiasis information and guidance:
- Santa Clara County Department of Environmental Health:
408-918-3400
Some Santa Clara Water is Fluoridated
Fluoridation adjusts naturally occurring fluoride in drinking water to the ideal level for protecting your teeth. Water purchased by the City from the SFPUC is fluoridated, while water from Valley Water is not.
If you’re in zip code 95054, you receive fluoridated water from the SFPUC that may be blended with unfluoridated well water. The area receiving a blend of water from both SFPUC and City wells are shown on the source water map included in this report. The majority of Santa Clara will continue to receive water without added fluoride. Contact your health care provider with any dental fluorosis concerns.
For more information, visit cdc.gov/fluoridation.
