Posted: August 28, 2026
The Science and Commitment Behind Water Quality
By Sophie James, Vice President, Water Quality
Water is the most essential resource we have. It is the glass of water your child drinks before school. It is the daily shower you take to stay clean.
At California Water Service, we’ve been dedicated to providing our customers and communities safe, clean, reliable water for 100 years. As we celebrate National Water Quality Month, we reflect on our everyday work behind the scenes to treat, test, and monitor our water sources to confirm they meet all applicable water quality standards to help protect the communities we serve.
How does Cal Water maintain the safety and quality standards of water?
At our state-of-the-art laboratory in San Jose, Calif., our team of chemists and microbiologists conducts more than 600,000 individual water quality tests every year. These tests detect organic and inorganic compounds as small as one part per trillion in water. To put that into perspective, that’s equivalent to looking for a single penny hidden somewhere among three football stadiums filled to the brim with other coins.
That scientific rigor extends beyond the walls of our laboratory. We work diligently to evaluate each water source on its own, identifying effective and cost-efficient treatment solutions for that specific supply. In some areas, that means operating facilities equipped with microfiltration, advanced oxidation, and ultraviolet treatment technologies. In others, a more straightforward approach, such as granular-activated carbon filtration, is the right answer.
What remains consistent across every source is our commitment to safety through disinfection. All of Cal Water’s water supply, whether it comes from surface water or groundwater sources, is treated to help protect it from waterborne diseases. Disinfection of drinking water has made many once-common diseases, like typhoid and cholera, a thing of the past in the United States and other developed countries.
Meeting applicable federal and state treatment and testing standards is something we take seriously; delivering on them with excellence and transparency is our commitment.
What are cross-connections, and what is Cal Water doing about them?
In public water distribution management, safeguarding water quality requires protection against cross-connections: points where non-potable water sources on a property can enter the clean public drinking water supply. Non-potable water often exists in everyday applications such as landscape irrigation systems, swimming pools, and business processes. When pressure shifts happen, backflow can also occur, drawing these liquids, chemicals, or gases backward into the public water supply. Without reliable prevention measures, these cross-connections pose a direct, unsafe contamination risk to the broader water system.
To help mitigate these risks, Cal Water maintains a robust cross-connection control program that identifies and isolates external hazards at the service boundary. Led by certified cross-connection control specialists, our teams systematically evaluate the risk profiles of commercial and residential connections. This risk evaluation allows us to identify potential hazards and confirm identified customers have the necessary backflow prevention assemblies installed.
We also oversee the mandatory annual testing of these backflow devices to confirm they maintain compliance with state and local plumbing regulations.
What causes changes in water taste, smell, and hardness?
Seasonal shifts in water supply or water that does not circulate at the dead-ends of mains can change the way water tastes or smells. These aesthetic (i.e., taste and odor) impacts are typically the result of natural source changes, warmer weather, or routine chlorination, which is one of the best ways to sanitize water from harmful pathogens. Similarly, hard water—defined by its mineral concentration—may impact soap lathering, household plumbing, or industrial processes.
Although changes in water taste, smell, and hardness may be unpleasant, they are nearly always aesthetic issues only and do not pose a health risk. Choosing to treat hard water, for example, is purely an aesthetic preference, and users should be mindful that some softening systems can increase sodium levels and pose challenges to wastewater treatment.
By focusing on the facts behind everyday water characteristics, we can foster a more accurate understanding of and confidence in our most essential resource.
What are PFAS and how is Cal Water addressing this issue?
As the regulatory landscape surrounding emerging contaminants shifts, certain per- and polyfluoroalkyl substances (PFAS) have become a central focus for water utility management, governance, and public health policy. PFAS refers to a broad class of synthetic compounds historically manufactured for use in water-, grease-, and stain-resistant applications. Due to their persistent chemical structure, these “forever chemicals” have migrated into groundwater sources, posing long-term operational and public health challenges.
While we didn’t cause PFAS to get into drinking water, we are committed to implementing treatment to reduce or remove them consistent with federal and state regulations. To tackle PFAS contamination, we take a proactive approach that blends early detection, operational safety, and aggressive policy advocacy. Well ahead of federal deadlines, we voluntarily tested every active water source in our systems and removed from service the small number of sources that exceeded public health guidelines until proper treatment could be installed. To help protect customers from the high costs of PFAS treatment, we are also actively pursuing state and federal grants and have pursued litigation against PFAS manufacturers to hold them financially accountable. Additionally, we are advocating for strict laws that would ban PFAS in commercial products.
Cal Water’s annual water quality reports dive deeper into our commitment to provide safe, clean, and reliable water – not only for the past century but also into the next 100 years. To learn more about how we help protect the water we provide to the communities we serve, visit calwater.com/waterquality.
