The tap water supplied by the Philadelphia Water Department (PWD) is considered safe to drink and consistently meets or exceeds all water quality standards set by the Environmental Protection Agency (EPA). The department operates under strict federal and state guidelines, conducting daily testing across its system to monitor for numerous contaminants. While the water is safe when it leaves the treatment plants, localized issues can occur at the point of use due to household plumbing.
Where Philadelphia Water Comes From and How It Is Treated
Philadelphia’s drinking water originates from two major surface water sources: the Schuylkill River and the Delaware River. These rivers supply three major treatment plants—Baxter, Queen Lane, and Belmont—which process hundreds of millions of gallons of water daily. The city draws approximately 58% of its water from the Delaware River at the Baxter plant, with the remainder sourced from the Schuylkill River. This dual-source system provides resiliency, allowing the PWD to adjust intake based on conditions in either river.
The raw river water undergoes a process to make it potable. Treatment begins with coagulation, where chemicals are added to clump tiny particles together, followed by sedimentation, which allows these heavier clumps to settle out. The water then passes through filters composed of layers of sand, gravel, and carbon to remove finer particles. Finally, the water is disinfected, primarily using chloramine (a combination of chlorine and ammonia), to kill any remaining microorganisms and maintain water quality. Zinc orthophosphate is also added to coat pipes and control corrosion before the water travels through the main lines.
Regulatory Compliance and Testing Standards
The safety of Philadelphia’s water is regulated by the federal Safe Drinking Water Act, enforced locally by the Pennsylvania Department of Environmental Protection (DEP). PWD scientists conduct constant monitoring, testing for compliance with over 90 regulated contaminants. The city submits test results monthly or annually to the state to demonstrate adherence to all legal requirements.
Public transparency is maintained through the annual Consumer Confidence Report (CCR), which details the previous year’s testing results and compliance status. The department also monitors for emerging threats, such as per- and polyfluoroalkyl substances (PFAS). While PWD meets current state regulations for two common PFAS compounds (PFOA and PFOS), it is proactively testing and planning for major treatment plant upgrades. This action is necessary to meet the much stricter federal Maximum Contaminant Levels (MCLs) for PFAS that the EPA has finalized and which will become enforceable soon.
The Impact of Aging Infrastructure and Lead Pipes
The risk to tap water quality in older cities like Philadelphia occurs after the water leaves the main distribution system. Water that is lead-free from the treatment plant can pick up lead as it passes through the final plumbing into the home. This contamination happens primarily due to the presence of lead service lines (LSLs), which connect the street water main to a property. Lead solder used in older household plumbing, especially in buildings constructed before 1986, is another common source.
The PWD uses corrosion control by adding zinc orthophosphate to the treated water, which forms a protective layer on the interior of metallic pipes. This coating significantly reduces the amount of lead that can leach into the water, and testing shows the treatment is generally effective. However, corrosion control is less effective when water sits stagnant in the pipes or when hot water is used. Since there is no safe level of lead exposure, the presence of LSLs remains a significant public health concern.
The Philadelphia Water Department is working toward eliminating this risk, with a long-term goal of replacing all known lead service lines by 2038. The city provides a zero-interest loan program, called HELP, to assist homeowners with the cost of replacing the portion of the LSL that they own. Residents are encouraged to use the PWD’s online map tool to check the probable material of their service line.
Actionable Advice for Residents
Residents can take simple, low-cost steps to mitigate potential lead exposure, especially in older homes.
- Flush the pipes by running the cold water tap for three to five minutes before using it for drinking or cooking. This step is particularly important in the morning or anytime the water has been sitting unused for more than six hours.
- Never use hot water from the tap for consumption, including for making baby formula or cooking, because heat causes lead to dissolve more quickly from plumbing.
- If you are concerned about your home’s specific risk, the PWD offers free testing kits to residential customers.
- For an added layer of protection, consider using a water filter certified by an organization like NSF International to remove lead, such as a carafe, faucet-mount, or under-sink unit.