If you live in Philly and want to know information about your tap water quality, start with the latest consumer confidence report , which is required to be produced annually by every community water system in the country. Most people never read them, but the reports provide essential information about drinking water quality.
Author
- Christine Kirchhoff
Associate Professor of Civil and Environmental Engineering and Law, Policy, and Engineering, Penn State
Like other large water systems, the Philadelphia Water Department publishes this information online, including the most recent 2025 drinking water quality report . The report provides an overview of Philly's drinking water from source to tap. It reports that levels of approximately 100 regulated contaminants all meet federal standards .
As an interdisciplinary scientist and engineer, I study drinking water infrastructure and how science gets translated into policy and decision-making.
While the Philadelphia Water Department report is a good place to start, knowing what it tells you and where there may be gaps requires some background on how drinking water is regulated.
How drinking water gets regulated
In the U.S., drinking water is regulated under the Safe Drinking Water Act , which set limits for just over 20 contaminants when it became law in 1974.
Subsequent amendments and regulatory processes have brought the total to about 100 . That's still a small number compared to the approximately 700 disinfection byproducts , the tens of thousands of chemicals in commercial use in the U.S. today, or other contaminants of emerging concern .
While not all of these compounds end up in drinking water in amounts that can harm public health, the U.S. Environmental Protection Agency's regulatory process is designed to be reactive, not proactive.
Before setting a limit, the EPA must demonstrate that a contaminant may cause adverse health effects, that it occurs at levels that are a public health concern, and that regulation would meaningfully reduce risk.
This process is repeated contaminant by contaminant, though a single glass of tap water may contain dozens of trace contaminants at once. The EPA has recently moved partly toward regulating mixtures of contaminants. The 2024 federal PFAS rule set individual limits for six PFAS compounds and also regulated four of them as a mixture. However, proposed changes to the 2024 federal PFAS rule include rescinding the mixture provision.
Goals versus limits
Federal drinking water standards involve two numbers for each contaminant. The maximum contaminant level goal, or MCLG, is the concentration at which the contaminant is believed to pose no significant risk to health in people who drink that water every day for 70 years.
For chemicals classified as possible human carcinogens, MCLGs are typically set at a level where drinking the water daily for 70 years would cause one additional cancer case per 1 million people above the background rate.
However, MCLGs are nonenforceable. Enforceable drinking water limits, also called maximum contaminant levels, or MCLs, are often higher than MCLGs because they take cost and feasibility into account.
Levels of forever chemicals
Two forever chemicals, PFOA and PFOS , deserve attention first. Both are types of perfluoroalkyl and polyfluoroalkyl substances, commonly called PFAS . PFAS are a family of synthetic chemicals widely used in consumer products. They persist in the environment and accumulate in the body.
The 2025 report from the Philadelphia Water Department shows Philly's highest reported levels of PFOA at 6.1 parts per trillion, or ppt, and PFOS at 4.6 ppt. Both are above the new federal limit of 4 ppt .
But Philly remains in compliance. Meeting the federal limit is not required until 2029, and the EPA has proposed extending that deadline to 2031 .
The levels are well below Pennsylvania's limits of 14 ppt for PFOA and 18 ppt for PFOS .
Encouragingly, the Philadelphia Water Department is expanding its capacity to remove PFAS systemwide using powdered activated carbon. Small-scale tests have shown that powdered activated carbon can be effective for removing PFOA and PFOS, though effectiveness in real treatment conditions depends on dosing, contact time and other factors.
Lead, disinfectants and sodium
Lead in drinking water comes from lead leaching into the water from service lines leading from the water main to your house or from plumbing inside your home. Lead can cause serious health problems, and it accumulates in the body.
As required by the Lead and Copper Rule , the Philadelphia Water Department's treatment includes corrosion control that forms a protective coating on the inside of pipes. This reduces the amount of lead that leaches into drinking water from lead service lines. Homes built before a 1986 federal ban on lead pipes and solder carry the most risk, as do homes with lead service lines. More recent brass fixtures could legally contain small amounts of lead until 2014.
The Philadelphia Water Department is required to collect samples from homes in Philly with lead service lines every three years. Testing in 2025 showed 90% of sampled homes were at or below 2 parts per billion, or ppb. That's well under the 15 ppb EPA action level. But testing results ranged from 0 to 21 ppb, meaning some homes with lead service lines had measurable lead in their water.
The maximum contaminant level goal for lead is zero because no safe level of childhood lead exposure has been determined.
Chemical disinfection keeps water safe across Philly's 3,000 miles of pipe but produces byproducts linked to increased cancer risk . These byproducts form when the disinfectant, in this case sodium hypochlorite, reacts with organic matter remaining in the water after treatment. Levels rise the longer water sits in the pipes.
The Philadelphia Water Department's 2025 annual averages were 51 ppb total trihalomethanes and 41 ppb haloacetic acids - both well under federal limits of 80 and 60 ppb, respectively. However, individual samples exceeded those limits. This suggests some homes further out in the distribution system may experience elevated levels.
Finally, sodium levels are a concern for people with sodium-restricted diets, including those with hypertension, heart failure or kidney disease. The American Heart Association recommends that people in these groups limit sodium intake to 1,500 milligrams per day. Depending on which plant serves you, Philly tap water carries 4 to 44 milligrams of sodium per 8-ounce glass. Over eight glasses a day, that's roughly 30 to 350 milligrams, or up to nearly 25% of the recommended daily limit.
What you can do
Reducing your household exposure to drinking water contaminants isn't difficult.
A carbon filter certified to NSF/ANSI Standard 53 will measurably reduce disinfection byproducts, PFOA and PFOS, and lead. A certified carbon filter for a pitcher, faucet or refrigerator works well to reduce levels in drinking water; reverse osmosis does more, but it costs more and wastes water.
In addition, if your home has a lead service line or older plumbing, the Philadelphia Water Department recommends running cold water from the tap for 3-5 minutes when it has been unused for more than six hours before drinking or cooking with it. This flushes out water that has been in contact with plumbing.
The Philadelphia Water Department offers free lead testing of tap water on request . The Centers for Disease Control and Prevention and EPA recommend that children at risk for lead exposure should have their blood lead levels assessed.
Sodium is a different case: Standard carbon filters don't remove it, but an ion-exchange pitcher, such as ZeroWater, or a reverse osmosis system will.
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Christine Kirchhoff does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
