Boston Water Quality Report

Boston's drinking water, supplied by the MWRA from the Quabbin and Wachusett Reservoirs, faces quality challenges primarily from aging infrastructure, lead service lines in older neighborhoods, and disinfection byproducts despite its pristine source water.

Water Source

Quabbin Reservoir, Wachusett Reservoir

Lead Service Lines

Approximately 21,000 estimated

Last Updated

March 22, 2025

Utility Provider

Massachusetts Water Resources Authority (MWRA)

What Boston Residents Should Know

Boston's drinking water, supplied by the Massachusetts Water Resources Authority (MWRA), originates from the protected Quabbin and Wachusett Reservoirs located in central Massachusetts. These pristine water sources provide high-quality source water that requires minimal treatment compared to many other major U.S. cities.

Despite these advantages, Boston faces water quality challenges primarily related to its aging infrastructure. The city's water distribution system includes pipes dating back to the late 1800s, with approximately 21,000 lead service lines still in use. These lead pipes, particularly prevalent in neighborhoods with pre-1940s housing like Beacon Hill, the South End, and Dorchester, can contribute to elevated lead levels in tap water.

Additionally, the disinfection process necessary to maintain water safety can create byproducts such as trihalomethanes (THMs) and haloacetic acids (HAAs) that may pose health concerns. While the MWRA has implemented advanced treatment techniques to minimize these byproducts, residents should be aware of these potential issues when considering their drinking water options.

21,000+

Lead Service Lines Estimated Citywide

5.7 ppb

Average Lead Levels (90th Percentile)

56 ppb

Highest THM Levels Detected

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Key Contaminants Found

These substances have been detected in Boston's water supply at levels that may be concerning for some residents.

Lead

Near Limit in Some Areas

Source: Lead service lines, lead solder in plumbing, and older fixtures in pre-1986 buildings

Health Effects: Developmental delays in children, learning disabilities, reduced IQ, kidney problems, high blood pressure

Boston Levels: Average 5.7 ppb (90th percentile), with approximately 7% of samples exceeding the EPA action level

EPA Limit: Action level 15 ppb, but no safe level exists

Total Trihalomethanes (TTHMs)

Below Limit, But Present

Source: Byproducts formed when chlorine used to disinfect water reacts with organic matter

Health Effects: Potential increased risk of cancer with long-term exposure, liver and kidney problems

Boston Levels: 42-56 ppb, varying by location and season

EPA Limit: 80 ppb

Haloacetic Acids (HAAs)

Below Limit, But Present

Source: Byproducts formed when chlorine used to disinfect water reacts with organic matter

Health Effects: Potential increased risk of cancer with long-term exposure, reproductive effects

Boston Levels: 18-32 ppb in most areas, higher during summer months

EPA Limit: 60 ppb

Copper

Below Limit

Source: Corrosion of household plumbing systems, erosion of natural deposits

Health Effects: Short-term exposure: gastrointestinal distress. Long-term exposure: liver or kidney damage

Boston Levels: 0.11 ppm (90th percentile)

EPA Limit: Action level 1.3 ppm

Neighborhood Variations

Water quality can vary significantly across Boston's diverse neighborhoods, primarily due to differences in infrastructure age, pipe materials, and building construction era.

Water Quality by Area

Neighborhood	Risk Level	Buildings Pre-1986	Notable Concerns
Beacon Hill	High	92%	Lead, Aging Infrastructure
South End	High	88%	Lead, Copper
Dorchester	Medium	76%	Lead, THMs
Roxbury	Medium	72%	Lead, HAAs
Jamaica Plain	Medium	65%	Lead, THMs
Back Bay	Medium	82%	Lead, Copper
Allston/Brighton	Low	58%	THMs (Low Levels)
Seaport District	Low	12%	HAAs (Low Levels)

Data based on MWRA sampling and Massachusetts housing statistics.

Recommended Action Steps

Based on Boston's water quality data, we recommend these actions to protect yourself and your family.

Check Your Service Line Material

Boston's Lead Service Line Replacement Initiative offers free inspections to determine if your home has lead pipes. Homes built before 1940 in neighborhoods like Beacon Hill, South End, and Dorchester are at highest risk.

Lead Service Line Information

Flush Your Pipes After Periods of Non-Use

If water hasn't been used for several hours (like first thing in the morning or when returning from work), run cold water for 2-3 minutes before using it for drinking or cooking. This helps flush out water that may have been sitting in lead pipes or fixtures.

Use Cold Water for Consumption

Always use cold water for drinking, cooking, and preparing baby formula. Hot water dissolves lead and other contaminants more readily from pipes. If you need hot water for food or drinks, heat cold water rather than using hot water directly from the tap.

Consider a Certified Filter

For homes with lead service lines or in high-risk neighborhoods, use an NSF/ANSI Standard 53 certified filter designed specifically for lead removal. Look for filters that also reduce disinfection byproducts like TTHMs for additional protection.

Filter Information

Participate in the Lead Replacement Program

Boston offers financial assistance programs to replace lead service lines. The city covers a portion of the replacement cost, and eligible homeowners may qualify for additional assistance or interest-free loans.

Financial Assistance Programs

Get Your Water Tested

Boston residents can request low-cost water testing through the MWRA or the Boston Water and Sewer Commission. If you live in a high-risk neighborhood or have children under six in your home, water testing is particularly important.

Water Testing Resources