Boston’s tap water system is frequently recognized for its exceptional quality, benefiting from a unique geographical advantage and a highly protected source water system. This sets its supply apart from many other large metropolitan areas. Understanding the journey the water takes, from its remote source to the kitchen faucet, helps consumers ensure their safety.
The Official Safety Status of Boston Tap Water
Boston’s tap water is consistently considered safe to drink, meeting or exceeding federal public health standards. The Massachusetts Water Resources Authority (MWRA) maintains this quality through comprehensive monitoring, conducting hundreds of thousands of tests annually. The water supply complies with regulations set forth by the U.S. Environmental Protection Agency (EPA) under the Safe Drinking Water Act. Boston’s system is frequently cited as one of the best large municipal supplies in the United States.
The Source: Understanding the MWRA System
The journey of Boston’s water begins in a vast, protected watershed located far outside the city limits. The primary sources are the Quabbin and Wachusett Reservoirs, situated approximately 65 and 35 miles west of Boston, respectively. This remote location and protected environment mean that the water is naturally high-quality from the start, with over 85% of the surrounding watershed covered by forest and wetlands.
The high-quality source reduces the level of treatment required. Water is channeled to the John J. Carroll Water Treatment Plant in Marlborough for processing. Treatment involves initial disinfection using ozone, followed by ultraviolet (UV) light treatment, which inactivates pathogens like Cryptosporidium. The MWRA also adds orthophosphate, which coats the inner surface of pipes to minimize corrosion and prevent lead from leaching into the water.
Addressing the Risk of Household Contamination
While the MWRA delivers lead-free water from its main system, the primary risk to consumers occurs within the localized, private plumbing infrastructure. Older homes built before the 1950s may have a private lead service line (LSL) connecting the water main to the building. Lead can enter the drinking water through the corrosion of these LSLs, lead solder, or brass fixtures, especially if the water has been standing in the pipes for several hours.
Residents can take several simple, actionable steps to mitigate this risk, such as always using cold water for drinking, cooking, and preparing baby formula. Before use, consumers should flush their water system by running the tap until the water feels noticeably cold to the touch, which clears out water that has been sitting in the private service line. The Boston Water and Sewer Commission (BWSC) offers a No Cost Private Lead Replacement Incentive Program to eligible property owners. This program fully funds the removal and replacement of the private portion of the lead service line, which is the most definitive way to address the localized risk.
Regulatory Compliance and Water Quality Reporting
The safety of Boston’s water is ensured by a comprehensive regulatory framework overseen by the EPA and the Massachusetts Department of Environmental Protection (MassDEP). These agencies prescribe the testing protocols and contaminant limits that the MWRA must follow. Compliance is maintained through continuous monitoring across the system.
Transparency is mandated through the federal Safe Drinking Water Act, which requires the annual publication of a Consumer Confidence Report (CCR). This report details the results of water quality testing from the previous calendar year, comparing contaminant levels to established safety standards. The MWRA and the BWSC make these annual CCRs publicly available, allowing residents to review the data and confirm the continued safety and compliance of their drinking water supply.