The water supply in the Los Angeles metropolitan area is safe to drink due to rigorous treatment and testing. The water delivered to homes generally meets or exceeds all mandated state and federal health standards. Los Angeles drinking water is sourced from complex, distant systems and local groundwater, subject to continuous quality monitoring.
The Journey of Los Angeles Water
The immense water needs of the Los Angeles area are met through a sophisticated system described as a “three straws and a bathtub” model. The vast majority of the water is imported from distant sources, traveling hundreds of miles through a massive network of aqueducts. These three primary “straws” include the Los Angeles Aqueduct (Owens Valley and Mono Basin) and the two major components of the Metropolitan Water District of Southern California (MWD) supply.
The MWD sources are the State Water Project (Northern California) and the Colorado River Aqueduct. This imported surface water blend accounts for the majority of the city’s supply. The “bathtub” represents the local groundwater basins, primarily in the San Fernando Valley, which provide a smaller but resilient portion of the total water portfolio.
The water travels through approximately 7,300 miles of mainlines and trunk lines maintained by the Los Angeles Department of Water and Power (LADWP). This vast infrastructure, parts of which date back over a century, is responsible for delivering the treated water to service connections throughout the city. Before distribution, the raw water undergoes extensive treatment processes, including filtration and disinfection, to ensure microbial safety.
Regulatory Framework and Quality Assurance
The safety of Los Angeles drinking water is governed by a multilayered regulatory system that establishes mandatory standards. At the federal level, the Environmental Protection Agency (EPA) enforces the Safe Drinking Water Act (SDWA), which sets Maximum Contaminant Levels (MCLs) for hundreds of substances. These federal rules represent the minimum required safety threshold for all public water systems.
California maintains rigorous oversight through the State Water Resources Control Board. The Board enforces both federal and California-specific drinking water laws. The state often establishes Public Health Goals (PHGs) that are more stringent than the federal MCLs, reflecting an ongoing effort to minimize public exposure to potential contaminants. This state-level authority ensures local water agencies are held to a high standard of water quality.
The local operational responsibility falls to the Los Angeles Department of Water and Power (LADWP), which manages the treatment and distribution. LADWP is required to conduct extensive testing, performing hundreds of thousands of tests on water samples annually. These tests confirm compliance with all mandated standards. The public can review the results in the annual Consumer Confidence Report (CCR), detailing the sources, testing results, and compliance status.
Current Safety Profile and Health Indicators
The proactive management of Los Angeles water involves continuously monitoring for specific substances, including those used for treatment and others that may occur naturally or as a result of human activity. To prevent the growth of microorganisms, LADWP uses chloramine, a disinfectant formed by combining chlorine and ammonia. This choice minimizes the formation of disinfection byproducts, such as trihalomethanes, which can be a concern when using traditional chlorine alone.
Despite meeting federal MCLs, certain naturally occurring or trace contaminants are detected at levels that may exceed more conservative health-based guidelines established by non-regulatory groups. For example, testing has detected trace amounts of arsenic (naturally occurring in groundwater) and hexavalent chromium (resulting from industrial processes). While the measured levels are below the EPA’s enforceable limits, the long-term health implications of these substances are subject to ongoing scientific review.
Emerging contaminants like Per- and Polyfluoroalkyl Substances (PFAS), often called “forever chemicals,” are also being actively monitored. The California State Water Resources Control Board has established response levels and new Maximum Contaminant Levels for several PFAS compounds, prompting water systems to increase their monitoring and treatment efforts. LADWP reports that it has not detected the regulated PFAS compounds in the water it serves. The presence of microplastics is another area of emerging concern, though standardized testing methods and specific health-based guidelines are still under development by the state.
Understanding and Mitigating Home Water Quality Issues
While the water leaving the municipal treatment plants is verified as safe, quality issues can arise after the water enters a home’s internal plumbing. Aesthetic problems, such as a noticeable taste or odor, are often attributed to the chloramine disinfectant, which remains in the water to maintain safety. Water hardness, caused by high levels of dissolved minerals like calcium and magnesium, is also common and can lead to scale buildup on fixtures and appliances.
A more serious, though localized, concern is the potential for lead contamination, which does not originate from the city’s main water lines. LADWP has confirmed that it does not have lead service lines in its distribution system, but lead exposure can occur in older homes built before 1985. The source is typically the lead solder used to join copper pipes or brass fixtures and faucets within the private plumbing.
Consumers concerned about water quality can take steps to mitigate potential issues. Flushing the tap by running the cold water for 30 seconds to two minutes, especially after the water has been sitting unused for several hours, helps to clear water that may have picked up metals from internal plumbing. For an extra layer of treatment, various home filtration systems are available. Reverse osmosis systems are effective at removing a wide range of contaminants, including trace lead and PFAS, while standard carbon filters can significantly reduce chloramine and other compounds that affect taste and odor.