Boston has one of the best drinking water systems in the United States. Full stop.
The Massachusetts Water Resources Authority (MWRA) supplies water to 3.1 million people across 51 communities in the greater Boston area. The source: the Quabbin and Wachusett Reservoirs in central Massachusetts — protected watersheds with limited development, surrounded by forests, managed specifically to produce clean drinking water.
The water is so clean at the source that the MWRA is one of only a handful of large water systems — alongside Seattle and Portland — that holds a filtration avoidance waiver from EPA. That means the water doesn’t need to pass through a filtration plant — it’s disinfected with ozone and UV treatment, pH-adjusted, and fluoridated, but it skips the coagulation-sedimentation-filtration process that most cities require.
So what’s the problem?
Lead in a Very Old City
Boston is one of the oldest cities in America. The housing stock in neighborhoods like Beacon Hill, Back Bay, South End, Charlestown, Dorchester, Roxbury, and Jamaica Plain dates to the 1800s and early 1900s — decades when lead was the standard material for water service lines and plumbing solder.
The MWRA treats water with sodium carbonate and carbon dioxide to raise pH and alkalinity, creating a protective film inside lead pipes that reduces leaching. This corrosion control program has been effective — the MWRA system’s 90th percentile lead levels have been well below the EPA action level.
But lead service lines still connect an estimated tens of thousands of homes to water mains across the MWRA service area. And corrosion control is a mitigation strategy, not an elimination strategy. Any disruption to water chemistry, physical disturbance of pipes, or prolonged stagnation can release lead particles.
Individual communities within the MWRA system are responsible for their own distribution infrastructure, which creates a patchwork of lead service line inventory and replacement progress. Boston proper, Cambridge, Somerville, and other older cities are all grappling with the LCRI mandate to inventory and replace all lead lines within 10 years.
PFAS: Low Levels, High Vigilance
PFAS contamination isn’t Boston’s headline water issue the way it is in places like Michigan or North Carolina. The Quabbin and Wachusett watersheds are relatively remote and protected from the industrial and military sources that produce the worst PFAS hotspots.
However, PFAS is everywhere in the environment, and testing under UCMR 5 and Massachusetts’s own monitoring programs has detected trace levels of PFAS compounds in some community water supplies within the MWRA system.
Massachusetts has been proactive on PFAS regulation. The state established a drinking water standard of 20 parts per trillion for the sum of six PFAS compounds — ahead of the EPA’s 2024 federal MCLs. The Massachusetts Department of Environmental Protection (MassDEP) has also been identifying and remediating PFAS contamination sites, particularly around military bases and airports.
Communities in the MWRA system that supplement their supply with local groundwater wells face more direct PFAS risk than those relying entirely on the Quabbin/Wachusett supply.
The Infrastructure Behind the Quality
Boston’s excellent water quality isn’t an accident — it’s the result of deliberate policy decisions dating back over a century.
The Quabbin Reservoir was created in the 1930s by damming the Swift River and flooding four towns in western Massachusetts. The displaced residents sacrificed their communities so that Boston could have clean water. It remains one of the most dramatic examples of infrastructure investment for public health in American history.
The MWRA’s modern investment portfolio includes:
- Deer Island Treatment Plant — One of the largest wastewater treatment facilities in the country, rebuilt in the 1990s after Boston Harbor was one of the most polluted urban harbors in America
- MetroWest Water Supply Tunnel — A $700 million deep-rock tunnel completed in 2003 that provides redundancy to the main aqueduct system
- Ongoing pipe replacement — The MWRA spends over $300 million annually on capital improvements to the water and sewer system
These investments are funded through water and sewer rates that are among the highest in the country. Boston-area residents pay for quality — but they get it.
What Boston-Area Residents Should Know
- Your source water is excellent. If you’re in the MWRA system, your water starts with some of the cleanest surface water in the country. The risk is in your building’s plumbing, not in the supply.
- Check your home’s plumbing. If you live in a pre-1950 building (common throughout Boston), you may have lead solder, lead service lines, or both. Contact your local water department for a service line check.
- Run the tap before drinking. Especially first thing in the morning or after the water has been sitting for hours. This flushes out water that’s been in contact with lead plumbing.
- Use cold water for cooking. Hot water dissolves more lead from pipes and fixtures.
- Consider a filter. Even in a great water system, a point-of-use filter provides an extra layer of protection — especially in older buildings.
- Private well owners in suburban and exurban communities should test annually and check MassDEP’s PFAS contamination maps.
The Bottom Line
Boston’s water system is a model for what’s possible when a city invests in source water protection, advanced treatment, and ongoing infrastructure renewal. The Quabbin Reservoir system is a genuinely exceptional resource.
The challenge — like everywhere in America — is lead in the last mile. The pipes connecting water mains to homes were built in an era when we didn’t understand the health consequences. Replacing them is the final step in making a great water system fully safe for every household it serves.
If you’re in an older home and want to know exactly what’s in your tap water, a certified water treatment professional can test it and help you decide if additional treatment makes sense.