Winthrop, Massachusetts
Winthrop Water Quality
MWRA reservoir water through the Town's own pipes. Winthrop's 2025 letter reports summer coliform results over the monthly limit — assessed and closed out with MassDEP — lead at 8.3 ppb at the 90th percentile, and 108 lead services relayed with copper.
Coliform over the limit Jul–Sep 2025 · lead 8.3 ppb · 108 lead services relayed.
The short answer
Winthrop drinks MWRA water, disinfected with chloramine. In 2025 the Town exceeded the 5% monthly coliform limit at multiple sites in July, August and September. MassDEP Level 2 Assessments were completed with no further action required; the suspected cause was warm water lowering disinfectant residuals.
Lead was 8.3 ppb at the 90th percentile — under the 15 ppb action level — and the Town relayed 108 lead or partial-lead services with copper during 2025. A tap test tells you what your own service line and plumbing contribute.
Get a free test
Tell us your Winthrop 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 Winthrop water comes from
The same reservoirs as Boston, through Winthrop's own pipes.
Quabbin and Wachusett Reservoirs
Winthrop purchases all of its water directly from the MWRA, whose sources are the Quabbin and Wachusett Reservoirs in central and western Massachusetts.
Treated at the Carroll plant
MWRA treats the water at the John J. Carroll Water Treatment Plant in Marlborough, including corrosion control and monochloramine disinfection.
Then Winthrop's own system
Two master meters feed the Town's pressure-reducing station, a 1-million-gallon standpipe and about 46 miles of main serving roughly 4,500 service connections.
What the 2025 Winthrop report actually says
Limits are fixed. Results are from MWRA's 2025 Drinking Water Test Results for Winthrop, including the Town letter — system-level figures, not a reading at your tap. A later report supersedes them.
Coliform — over the limit July to September
Winthrop tests 12 samples twice a month. In 2025 it exceeded the 5% monthly limit at multiple sites in July, August and September, which required MassDEP Level 2 Assessments.
Assessments done; cause suspected to be heat
The Town reports all assessments were completed and submitted, with no additional actions required. The suspected cause was warmer water lowering chlorine residuals; flushing and tank maintenance followed.
Lead — 8.3 ppb at the 90th percentile
The September 2025 round: 8.3 ppb at the 90th percentile (range 0.077–26.8 ppb), under the 15 ppb action level. One of twenty samples exceeded the action level.
Copper — 147 ppb
90th percentile across the same round (range 9.78–242 ppb) against a 1,300 ppb action level. No sample exceeded the copper action level.
108 lead services relayed in 2025
26 by Town crews and 82 under MWRA-funded Contract 12 (March–October 2025), each relayed with copper from the main to the meter.
Every remaining lead service identified
The letter says all remaining lead services are identified and that the Town removes at least 14% of the remainder each year. Its electronic inventory was accepted by MassDEP.
Winthrop next to Revere, Chelsea and Boston
Revere shares the MWRA supply but still listed hundreds of known lead services in 2025. Chelsea reported 2.41 ppb lead with an active dig-and-replace program, and Everett had replaced 411 lead services by the end of 2025. Boston is the regional MWRA hub. Winthrop's letter is the one on this site where the summer coliform line, not lead, is the headline.
Where these figures come from
Everything on this page traces to MWRA and the Town of Winthrop Department of Public Works.
- MWRA — 2025 Drinking Water Test Results, with the Town of Winthrop letter (PDF) — MWRA sources and treatment; Winthrop's coliform assessments, lead and copper results, lead-service relays, system size and maintenance programs.
Matching treatment to the finding
Winthrop's report supports checking your service line and good stale-water habits — not a default equipment sale.
Ask the DPW about your service line
Winthrop's inventory is available at the DPW office. Owners with lead services or questions can call 617-846-1341 ext. 2603. If your home is on the list, ask where it sits in the replacement schedule.
Run stale water after time away
The Town tied the summer coliform results to warm water and low disinfectant residuals and answered with flushing. At home, running water that has sat in the pipes for hours is a sensible habit — especially in summer.
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 disinfects with monochloramine. If taste or odour is the complaint, catalytic carbon or reverse osmosis is the right tool. Change cartridges on the maker's schedule.
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.
Winthrop water, answered plainly
Where does Winthrop's water come from?+
From the MWRA. Winthrop buys all of its treated water from the Quabbin and Wachusett Reservoirs and delivers it through two master meters, a pressure-reducing station and about 46 miles of Town main.
What happened with coliform in 2025?+
The Town's letter says Winthrop exceeded the 5% monthly total-coliform limit at multiple sample sites in July, August and September 2025. That triggered Level 2 Assessments, which were completed and submitted to MassDEP with no additional actions required. The suspected cause was warm water lowering chlorine residuals.
Is that the same as a boil-water order?+
No. Total coliform is an indicator that a pathway for contamination may exist; the letter describes assessments and corrective flushing, not a boil order. For current conditions, check with the Winthrop DPW.
Did Winthrop exceed the lead action level?+
No, in 2025. The September round showed 8.3 ppb at the 90th percentile against a 15 ppb action level, with one of twenty samples over. Copper also stayed under its action level.
How fast is Winthrop replacing lead services?+
108 full or partial lead services were relayed with copper in 2025 — 26 by Town crews and 82 under MWRA-funded Contract 12. The Town says it removes at least 14% of its remaining lead services each year.
Where do these figures come from?+
MWRA's 2025 Drinking Water Test Results for Winthrop, which includes the Town of Winthrop DPW Water Division letter (PWS 3346000). 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: hundreds of known lead services on the 2025 inventory.
Learn more →Chelsea water quality
MWRA neighbor: lead 2.41 ppb; 52 lead services removed in 2025.
Learn more →Everett water quality
MWRA city with 411 lead services replaced at no cost.
Learn more →Boston water quality
The regional MWRA hub Winthrop 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 a service line or older plumbing, chloramine taste or none of them. No charge, no obligation, and coverage confirmed at your address first.
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