Water quality in Santa Clara: What you need to know

Water touches just about every part of daily life in Santa Clara — from cooking and cleaning to keeping your family hydrated. But not all water is created equal. Because our city relies on a blend of local groundwater and imported sources, what comes out of your tap may have its own unique makeup. If you’ve ever noticed spots on dishes, a chlorine smell or just wondered what’s really in your glass, you’re not alone. Here’s what to know about Santa Clara’s water quality and what it means for your home.

Is it safe to drink tap water in Santa Clara?

Per federal requirements, the City of Santa Clara provides an annual Water Quality Consumer Confidence Report with information about where your water comes from, how it’s treated and water quality testing results. Santa Clara’s water supply is monitored, and 34 locations are tested every week in state-certified laboratories. The report confirms that all Santa Clara water sources meet or exceed federal and state standards, and discusses a few things to be aware of:

• Lead: Older household plumbing can still cause higher levels in some homes. Lead typically comes from pipes and fixtures, not the city’s supply, and can pose health risks.
• Bacteria, viruses and parasites: The San Francisco Public Utilities Commission (SFPUC) regularly tests its water for parasites like Cryptosporidium and Giardia. While trace amounts are sometimes detected, these levels are very low. Both organisms can cause short-term intestinal illness, with higher risks for children, older adults, and people with weakened immune systems.
• PFAS: PFAS, or per- and polyfluoroalkyl substances, are manmade chemicals used for their water- and stain-resistant properties in products like cookware, fabrics and food packaging. Because they break down very slowly, PFAS can persist in the environment for a long time and have potential health concerns. In Santa Clara, testing since 2019 has found no detectable PFAS in the city’s water supply.

Beyond the city’s own water quality report, further information on Santa Clara’s water quality is available through the Environmental Working Group (EWG), an independent nonprofit research organization that reviews water testing data from utilities across the country and compares results to its own health-based guidelines. These guidelines are often stricter than federal and state limits, which are based not only on health studies but also on treatment feasibility and cost.

According to EWG’s Tap Water Database for the City of Santa Clara, 13 contaminants were detected in recent testing, and eight of them exceeded EWG’s health guidelines. All levels remain within legal safety limits set by the EPA and California, but EWG’s thresholds reflect a more conservative view of long-term health protection.

The main contaminants exceeding EWG’s benchmarks were disinfection byproducts. These are substances formed when chlorine and other disinfectants react with natural organic matter in the water, and are common in treated municipal supplies nationwide. Some of the most notable include:

• Total Trihalomethanes (TTHMs): A group of chemicals including chloroform and bromodichloromethane, formed during water disinfection. Long-term exposure above health guidelines may increase certain cancer risks.
• Haloacetic Acids (HAA5 and HAA9): Another group of disinfection byproducts linked to potential liver and reproductive effects with high, prolonged exposure.
• Dichloroacetic and Trichloroacetic Acids: Specific haloacetic acids identified by EWG at levels above their health-based limits; both are regulated but often appear in trace amounts as a byproduct of chlorine treatment.

EWG’s findings don’t indicate regulatory violations or unsafe water, but they highlight how in-home filtration—especially carbon or reverse osmosis systems—can further reduce disinfection byproducts and other trace contaminants for those who want an added level of protection.

Sources of Santa Clara’s drinking water

Santa Clara’s drinking water comes from three primary sources. The city draws from protected groundwater wells within its boundaries. Water also comes from local reservoirs and rivers connected to the Sacramento–San Joaquin Delta through the water wholesaler Valley Water. In addition, snowmelt from the Sierra Nevada Mountains is delivered by SFPUC’s Hetch Hetchy System. These sources are blended and used interchangeably to supply an average of 15 million gallons of water per day to the community.

Valley Water mainly serves the southwest area of Santa Clara. According to the City of Santa Clara’s 2024 Water Quality Consumer Confidence Report, treatment for this supply includes dual-media filtration using coal and sand, followed by disinfection using chlorine and chloramine.

SFPUC water is typically delivered to neighborhoods north of Highway 101 and uses multiple levels of treatment to ensure that your drinking water is protected. These include:

• Fluoridation, which supports dental health
• Ultraviolet (UV) light and chlorine treatment to kill harmful microorganisms
• Chloramination to maintain long-lasting disinfection
• pH adjustment which helps to prevent pipe corrosion

Most of the community is served by groundwater wells that draw from deep underground aquifers that are naturally replenished by rainwater and filtered through layers of sand, gravel and silt. This supply is then monitored and disinfected to meet drinking water standards.

Should you filter tap water in Santa Clara?

Across North America, municipal tap water is treated to meet government safety standards. Government bodies in the U.S. and Canada establish frameworks like the National Primary Drinking Water Regulations and Guidelines for Canadian Drinking Water Quality to guide how water is monitored and maintained. But as detailed above, that doesn’t always mean it’s completely free of concerns once it reaches your tap.

Additionally, emerging concerns like microplastics, pharmaceuticals and PFAS (known as “forever chemicals”) are still being researched and, in many cases, aren’t yet regulated—though new rules may be on the horizon. Because of this, many public systems aren’t currently equipped to filter them out. Additionally, even treated water can pick up contaminants such as lead or iron as it travels through aging infrastructure or household plumbing.*

Although Santa Clara consistently provides high-quality water that meets federal safety standards, Culligan filtration and softening systems help enhance your tap water by addressing not only potential contaminants but issues related to taste, odor and hardness as well. These aesthetic issues aren’t covered by federal regulations, so municipalities aren’t required to treat them. They could include a bleach-like taste or smell from chlorine, a rotten-egg smell or rust stains from sulfur or iron, or bitter or salty taste from TDS (dissolved salts, metals and minerals).

If you’ve noticed these or just want to feel more confident about your water quality in general, it may be time to look into water filtration solutions. Depending on the nature of the problem, you can choose:

• Whole house filtration: Installed where your main source of water enters your home, these systems treat individual issues that affect water throughout your home, like sediment, iron, nitrate, arsenic, PFAS and more.
• Reverse osmosis drinking water filtration: These systems focus on comprehensive drinking water filtration to address a wide range of potential water issues—most of which you can’t see, taste or smell, but wouldn’t want in your glass. Culligan’s most advanced RO systems are certified to reduce more than 90 contaminants, including lead, bacteria, PFAS and more.

To determine which water filtration system is right for your home, it’s a good idea to start with a professional water test. Results from the water test will help you determine if contaminants are present, what symptoms they cause and how to address them.

What about water hardness in Santa Clara?

Although it doesn’t negatively impact drinking water, hard water causes mineral buildup in pipes and appliances; makes soap, shampoos and detergents less effective; and leaves spots or residue on dishes and fixtures. Over time, buildup from hard water can reduce water pressure and lower the efficiency or lifespan of household appliances like dishwashers and water heaters.

According to the Santa Clara Valley Water District, water in Santa Clara County is considered very hard. Per their website, the hardness in groundwater in Santa Clara County averages over 250 mg/L and the average hardness of the District’s treated surface water is less than 120 mg/L. Based on standard water hardness measurements, this would be considered noticeably hard water.

Water softeners can address issues from hard water, and your local Culligan expert can recommend the right system for your home based on results from your free water test.

Take the next steps to improve your water

While Santa Clara’s water meets federal safety guidelines, you may still want to take steps to improve taste, reduce potential contaminants and protect your home from hard water buildup. A free, in-home water test from the local water experts at Culligan of Santa Clara can identify your home’s specific needs and offer recommendations for the best solutions to improve water quality throughout your home.

Ready to get started? Schedule your free, in-home water test and consultation.

*Contaminants may not be present in your water.