Chelsea, Massachusetts
Chelsea Water Quality
MWRA reservoir water through Chelsea's own pipes. The City's 2025 letter shows lead at 2.41 ppb at the 90th percentile — and 165 test pits plus 52 lead services removed that year under a free replacement program.
Lead 2.41 ppb at the 90th percentile · 165 test pits · 52 lead services removed in 2025.
The short answer
Chelsea drinks MWRA water from the Quabbin and Wachusett Reservoirs, disinfected with chloramine. Its 2025 lead result was 2.41 ppb at the 90th percentile — under the 15 ppb action level — with zero of 21 samples over the limit.
The bigger local story is the field program: 165 test pits and 52 lead services removed in 2025, under a free replacement program that has run since 2018. Check your service line on the City dashboard first; a tap test then tells you what in-house plumbing still contributes.
Get a free test
Tell us your Chelsea address. We confirm coverage first, then schedule a licensed technician to test at your tap — no charge, no obligation.
What filtration does — and does not
Softening, carbon and reverse osmosis solve different problems. A filter is not a substitute for replacing a lead service line.
Where Chelsea water comes from
The same reservoirs as Boston, through Chelsea's own pipes.
Quabbin and Wachusett Reservoirs
Chelsea purchases all of its drinking water from the MWRA, whose sources are the Quabbin and Wachusett Reservoirs in central and western Massachusetts.
Treated at the Carroll plant
MWRA's John J. Carroll Water Treatment Plant in Marlborough disinfects with ozone and UV, adds fluoride, adjusts pH and alkalinity to reduce lead corrosion, and finishes with monochloramine.
Then Chelsea's own distribution
Five MWRA master meters feed about 56 miles of City mains (6–20 inches), roughly 575 hydrants and more than 5,100 curb stops into each service.
What the 2025 Chelsea report actually says
Limits are fixed. Results are from MWRA's 2025 Drinking Water Test Results for Chelsea, including the City letter — system-level figures, not a reading at your tap. A later report supersedes them.
Lead — 2.41 ppb at the 90th percentile
Chelsea's 2025 round (20 residences plus two schools): 2.41 ppb at the 90th percentile (range ND–13.7 ppb), under the 15 ppb action level. Zero of twenty-one samples exceeded the action level.
Copper — 70.9 ppb
90th percentile across the same sites (range 3.56–86.1 ppb) against a 1,300 ppb action level. No sample exceeded the copper action level.
165 test pits and 52 lead services removed in 2025
The City letter counts 165 investigatory test pits and 52 lead service lines removed in 2025 as part of compiling the Lead Service Line Inventory.
Free lead replacement since 2018
Chelsea began replacing the private side during main projects in 2017 and, in September 2018, launched a multi-year program to replace remaining lead services at no cost to owners or tenants.
Aging unlined cast-iron mains
About 70% of Chelsea's mains are over 50 years old and an estimated 47% are unlined cast iron. Tuberculation is not a health violation, but it can restrict fire flow and give water a rusty or yellow/red look.
Coliform — met every month
Chelsea monitors 11 distribution sites every week. It stayed under the 5% monthly positive limit every month in 2025.
Chelsea next to Revere, Malden and Boston
Where these figures come from
Everything on this page traces to MWRA and the City of Chelsea Department of Public Works.
- MWRA — 2025 Drinking Water Test Results, with the City of Chelsea letter (PDF) — MWRA sources, treatment and detected contaminants; Chelsea's lead and copper results, test-pit and lead-removal totals, main-age context and coliform compliance.
- City of Chelsea — Lead / service-line dashboard — public inventory view and verification scheduling.
Matching treatment to the finding
Chelsea's report supports checking your service line and a chloramine-aware filter choice — not a default equipment sale.
Check the City service-line dashboard first
Chelsea posts a public dashboard of service-line materials at chelseama.gov under Community / Lead. If yours shows lead, GRR or unknown, schedule a DPW verification before buying a filter.
City-funded lead replacement
The 2025 letter describes free replacement of remaining lead services. Contact Chelsea 311 or Public Works (617-466-4200) before paying a private plumber to dig the public-side line.
Certified lead filter as a stopgap
Until a lead service is replaced, a filter certified to reduce lead at the kitchen tap is the practical stopgap — not a substitute for the pipe.
Chloramine taste: catalytic carbon or RO
MWRA finishes with monochloramine. Ordinary carbon handles free chlorine better than chloramine. If taste or odour is the complaint, catalytic carbon or reverse osmosis is the right tool.
How the free test works
A licensed technician tests at your kitchen tap, walks the plumbing, and tells you which of the findings above applies to your house and which does not. There is no charge and no obligation.
Seamless Home is the licensed contractor of record on the work that follows. Installation is performed by vetted installing partners engaged as our subcontractors, and the workmanship obligation stays with us. Coverage is confirmed per service area rather than promised as blanket availability.
What a water treatment job with us covers
Installation and replacement of whole-home and point-of-use treatment, specified against what your water actually contains.
Sediment filtration
Installation of the first stage that protects everything downstream of it, sized to the service line and the household draw.
Softening
Installation of ion-exchange softening where hardness is the problem, including the drain connection the plumbing code treats as indirect waste.
Carbon filtration
Installation of carbon stages for taste, odour and disinfection by-products, specified from your utility's own water quality report.
Reverse osmosis
Point-of-use installation at the kitchen sink where the target is dissolved solids rather than whole-home flow.
Disinfection
Installation of UV or equivalent treatment where the supply is a private well or is otherwise not continuously disinfected.
System replacement
Replacing equipment that has reached the end of its service life, including the discharge and air gap details an inspector looks at.
This is installation and replacement work, specified from a published water quality report or a test of your supply — not from a sales chart. Coverage is confirmed per service area rather than promised as blanket availability.
What the work actually looks like
Treatment equipment is plumbing. Most of the job is the connection, the drain and the code detail behind it.
Chelsea water, answered plainly
Where does Chelsea's water come from?+
From the MWRA. Chelsea buys all of its treated water from the Quabbin and Wachusett Reservoirs, treated at the John J. Carroll plant in Marlborough, and delivers it through the City's own distribution system.
Did Chelsea exceed the lead action level?+
No, in the 2025 round. The City letter shows 2.41 ppb at the 90th percentile against a 15 ppb action level, with zero of twenty-one samples over the limit. Copper also stayed under its action level.
How aggressive is Chelsea's lead program?+
In 2025 the City dug 165 test pits and removed 52 lead services, and it has offered free lead-service replacement since September 2018. It was also an EPA Get the Lead Out partner community through summer 2025.
Why does my water look rusty?+
The letter notes that about 47% of Chelsea's mains are old unlined cast iron. Tuberculation (rust growth inside the pipe) can give water a rusty or yellow/red appearance without making it a health violation — and it can restrict fire flow.
Does Chelsea use chlorine or chloramine?+
Chloramine. MWRA disinfects with monochloramine before the water reaches Chelsea's meters.
Where do these figures come from?+
MWRA's 2025 Drinking Water Test Results for Chelsea, which includes the City of Chelsea Department of Public Works letter (PWS 3057000). Third-party aggregators are not used. A later report supersedes these figures.
Related resources
Home water purification and treatment
The national service page behind this one.
Learn more →Revere water quality
Next door: 362 known lead services still on the 2025 inventory.
Learn more →Malden water quality
MWRA water with a fall 2025 lead action-level exceedance.
Learn more →Boston water quality
The regional MWRA hub Chelsea buys from.
Learn more →All home services
Water, battery, HVAC and solar under one licensed contractor of record.
Learn more →Get a free test at your tap
A licensed technician tests at your kitchen tap and tells you which findings apply to your house — lead from older plumbing, chloramine taste or none of them. No charge, no obligation, and coverage confirmed at your address first.
Get a free test