Belmont, Massachusetts
Belmont, MA Water Quality
MWRA reservoir water through 90.1 miles of Town main. Belmont found only four lead service lines and is replacing them, so the local story is the age of its mains.
Lead 90th 1.5 ppb (0 of 20 over) · 4 lead lines, being replaced free · 22 main breaks in 2025.
The short answer
Belmont buys MWRA water from the Quabbin and Wachusett Reservoirs, disinfected with monochloramine. Byproducts are low, PFAS is well below the state standard, and lead was 1.5 ppb at the 90th percentile with no home over the action level.
Lead service lines are nearly settled: the inventory found four, and the Town is replacing all of them at no cost. The bigger local factor is the pipes in the street. Crews repaired 22 main breaks in 2025, and that year's contract replaced unlined cast iron main laid between 1889 and 1924.
Get a free test
Tell us your Belmont 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
Sediment, carbon, catalytic carbon and reverse osmosis solve different problems. Belmont's letter points at old mains and chloramine taste more than at lead.
Where Belmont water comes from
MWRA reservoirs, Town pipes.
Quabbin and Wachusett Reservoirs
Belmont buys all of its water from the MWRA. It starts in the Quabbin Reservoir, passes through the Wachusett Reservoir and is treated before it reaches town.
Four master meters
MWRA meters the water into Belmont at four master meters. MWRA disinfects it with monochloramine, which averaged 1.99 ppm in 2025.
90.1 miles of Town main
The DPW Water Division (PWS 3026000) maintains 90.1 miles of main, 879 hydrants and 2,886 gate valves, serving 7,395 service connections.
What the 2025 Belmont report actually says
Limits are fixed. Results are from the MWRA 2025 water quality report and the Town of Belmont's letter. They are system-level figures, not a reading at your tap.
Four lead service lines, being replaced
Belmont's service-line inventory found no unknown and no galvanized lines, and four homes with a lead line. The Town is replacing all four with copper at no cost to the owners. Three were done when the report was written.
Lead 1.5 ppb at the 90th percentile
Samples ranged from 0.1 to 2.3 ppb, with 0 of 20 homes over the 15 ppb action level. Copper was 67.7 ppb at the 90th percentile, none over.
22 main breaks in 2025
Town crews repaired 22 water main breaks and 12 service line breaks in 2025. Breaks and repairs can stir up sediment, which shows up as discolored water at the tap.
Mains from 1889 to 1924
The 2025 replacement contract covered five streets of 6-inch unlined cast iron main dating from 1889 to 1924. They were replaced with 8-inch ductile iron.
Monochloramine, not free chlorine
MWRA's disinfectant averaged 1.99 ppm. It lasts longer in pipes than chlorine and is harder for basic pitcher filters to remove.
Low byproducts, PFAS below standard
MWRA reported TTHMs at 16.1 ppb and HAA5 at 15.8 ppb against limits of 80 and 60, and PFAS well below the Massachusetts PFAS6 standard of 20 ppt. Belmont had no positive coliform samples in 2025.
Belmont next to Watertown, Arlington and Lexington
All four buy the same MWRA water. The difference is in the town pipes. Lexington is partway through a larger lead service line replacement, while Watertown and Arlington each report their own local results. Belmont's lead list is down to four homes, so for most Belmont houses the questions are the age of the main on the street and the plumbing inside.
Where these figures come from
Everything on this page traces to the MWRA and the Town of Belmont.
- MWRA — Annual Water Quality Report for 2025, with the Town of Belmont letter (published June 2026, PDF) — source, lead and copper results, the service-line inventory, main breaks and replacement work, and MWRA-wide results.
- MWRA — Annual Water Quality Test Results — the index of community reports.
Matching treatment to the finding
Belmont's letter supports a test and, on some streets, sediment filtration. It does not support a default equipment sale.
Settle the service line first
Belmont's inventory is online at belmont-ma.gov. If yours was one of the four lead lines, the Town is handling the replacement. Everyone else can rule lead service lines out.
Sediment filtration for an old-main street
If your street still has older cast iron main, a whole-house sediment stage catches the rust and grit that main breaks and hydrant work can send through.
Catalytic carbon for chloramine taste
Monochloramine is the taste most Belmont homeowners notice. Catalytic carbon, sized for chloramine, handles it better than standard carbon.
Test at the tap first
The Town's figures are system-wide. A test at your kitchen tap shows whether your own plumbing, solder or fixtures add anything.
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.
Belmont water, answered plainly
Where does Belmont's water come from?+
Belmont buys all of its water from the MWRA. It comes from the Quabbin Reservoir through the Wachusett Reservoir and enters town at four MWRA master meters. The Town's DPW Water Division distributes it through 90.1 miles of main.
Does Belmont have lead service lines?+
Very few. The Town's inventory found no unknown and no galvanized lines, and four homes with a lead service line. The Town is replacing all four with copper at no cost to the owners, and three had been replaced when the 2025 report was written.
What were Belmont's lead and copper results?+
Lead ranged from 0.1 to 2.3 ppb, with a 90th percentile of 1.5 ppb. Copper ranged from 6.49 to 89.9 ppb, with a 90th percentile of 67.7 ppb. None of the 20 homes sampled was over either action level.
Why does my Belmont water sometimes look discolored?+
Main breaks, hydrant work and old unlined cast iron main can all stir up sediment. Belmont repaired 22 main breaks in 2025 and is replacing old main street by street under a program that began in 1995. If discoloration is frequent, a test and a sediment stage are reasonable next steps.
Is there PFAS in Belmont's water?+
MWRA reports trace amounts, well below the Massachusetts PFAS6 standard of 20 parts per trillion.
Where do these figures come from?+
From the MWRA Annual Water Quality Report for 2025 results with the Town of Belmont's letter (PWS 3026000), published June 2026. Third-party aggregators are not used.
Related resources
Home water purification and treatment
The national service page behind this one.
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MWRA water, mid-project on lead service lines.
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MWRA water with Watertown's own local results.
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MWRA water with Arlington's own local results.
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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 — sediment from older mains, chloramine taste or your own plumbing. No charge, no obligation, and coverage confirmed at your address first.
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