Pasadena Water and Power (PWP), the city-owned utility, is responsible for ensuring a safe and reliable water supply. Understanding the safety of the water involves looking at where the water originates, how it is treated, and the results of rigorous testing conducted throughout the year. This information provides a detailed overview of the water quality, regulatory standing, and available options for personal water treatment in Pasadena.
Current Safety Status and Regulatory Compliance
Pasadena tap water consistently meets or surpasses all mandated public health standards established by federal and state regulatory bodies. PWP operates under the oversight of the United States Environmental Protection Agency (EPA) and the California State Water Resources Control Board, Division of Drinking Water (SWRCB). These agencies set the Maximum Contaminant Levels (MCLs), which represent the highest concentration of a substance permitted in public drinking water systems.
The city’s laboratory staff conducts daily monitoring and analysis, processing over 200 water samples weekly to ensure continuous compliance. This extensive testing program covers more than 100 different constituents found in the water supply. The overall safety record is one of full compliance, meaning the water delivered to the customer is safe for consumption without additional treatment.
PWP makes the results of this monitoring publicly available through the annual Consumer Confidence Report (CCR) on Water Quality. This report details the sources of the water, the contaminants detected, and how those levels compare to the established regulatory limits. Residents can access the most recent CCR electronically on the PWP website.
Sources of Pasadena’s Water Supply
Pasadena’s water supply is drawn from two distinct sources, creating a dual system that enhances supply reliability. The local supply originates from groundwater pumped from the Raymond Basin, a natural aquifer underlying Pasadena and neighboring areas. This local resource typically accounts for approximately one-third of the city’s total water demand.
The remaining portion of the supply is imported surface water purchased from the Metropolitan Water District of Southern California (MWD). MWD draws this imported water from two major sources: the State Water Project (Northern California) and the Colorado River via the Colorado River Aqueduct.
The blend of groundwater and imported water means both sources are subject to different treatment requirements. Local groundwater is naturally filtered as rainwater percolates through the ground into the Raymond Basin. The imported surface water undergoes extensive treatment by MWD before being blended with the local supply.
Key Contaminants and Tested Levels
While Pasadena’s water is compliant with all legal standards, the testing reveals the presence of several substances that are routinely monitored. Disinfection byproducts, such as Total Trihalomethanes (TTHMs), are formed when chlorine-based disinfectants react with naturally occurring organic matter in the water. These compounds, which include chloroform and bromodichloromethane, are regulated by the EPA and the state, and PWP’s levels remain below the regulatory Maximum Contaminant Level (MCL).
Heavy metals are another category of concern, particularly lead and copper, which are often introduced by household plumbing rather than the municipal source. PWP has been consistently compliant with the Lead and Copper Rule, with the 90th percentile for lead testing at customer taps often reported as Non-Detect (ND). The utility maintains corrosion control measures to prevent these metals from leaching into the water from pipes.
A substance that often receives attention is Hexavalent Chromium, an unregulated contaminant that has a low Public Health Goal (PHG) set by the state. Recent testing data for the Pasadena system showed a typical range of 1.3 to 8.6 parts per billion (ppb). This is significantly lower than the federal MCL for total chromium, but higher than the state’s conservative PHG of 0.02 ppb.
Microbial contaminants, such as E. coli and total coliform, are monitored daily to ensure the disinfection process is working effectively. The municipal system reported zero positive samples for E. coli, confirming the integrity of the treatment and distribution process. Arsenic is another naturally occurring element detected at very low levels, averaging 0.460 ppb, which is far below the federal MCL of 10 ppb.
Home Filtration and Personal Water Safety Measures
For residents who desire an added level of assurance or a reduction in specific contaminants, home filtration is a viable option. Carbon-based filters, commonly found in pitcher filters or faucet-mounted units, are effective at removing many taste and odor-causing compounds, such as residual chlorine or chloramine. These filters work by adsorption, where the contaminants cling to the porous surface of the carbon.
More comprehensive systems, such as reverse osmosis (RO) units, can remove a broader range of dissolved solids and chemical contaminants, offering a high degree of purification. Whole-house filtration systems treat all water entering the home, providing consistent quality for both drinking and bathing. Any home filtration device requires regular maintenance, including timely filter replacement, to remain effective.
Mitigating the risk of lead exposure begins with managing home plumbing, as the city’s water mains are non-lead. If your home has older, lead-containing fixtures or solder, run the cold water tap for 15 to 30 seconds before using it for drinking or cooking. This action flushes out stagnant water that may have absorbed lead or copper from the internal plumbing. Always use only cold water for preparing food or baby formula, as hot water can increase the leaching of metals from pipes.