Window Washing in Boston
Boston's supply is extremely soft at 10 mg/L, under one grain per gallon and soft enough to be aggressive, so it is corrected with sodium carbonate.
Boston's water is extremely soft, so a drop that dries on glass leaves essentially nothing behind; streaks here come from technique, not the tap. July to October is the reliable window, before snow and road salt return. Access sets the price in old Boston, where bow fronts and narrow lanes add time before any glass is touched; a single-story exterior runs $380 to $620.
What the water means for the glass
Ten milligrams per litre is close to the practical floor for a municipal supply, and the consequence is liberating: a droplet of Boston tap water that dries on glass leaves essentially nothing behind. Every visible flaw in a finish here is therefore technique, timing or something the air deposited, and diagnosing it as water is a dead end. The one thing soft water does change is detergent behaviour — it lathers far more readily than most people expect, so the commonest cause of film on a Boston window is a heavy hand with the soap.
Boston tap water, by the numbers
| Hardness | 10 mg/L as CaCO₃ Soft — less than one grain per gallon, in the supplier's own words, as published by Boston Water and Sewer Commission, supplied by the Massachusetts Water Resources Authority. |
|---|---|
| pH | 9.7 |
| Alkalinity | 41.9 mg/L as CaCO₃ |
| Iron | 0.0225 mg/L |
| Manganese | 0.005 mg/L |
| Sodium | 35.6 mg/L |
| Chloride | 30.1 mg/L |
| Total dissolved solids | 114 mg/L |
| Disinfectant | chloramine |
| Source and treatment | The Quabbin Reservoir, holding 412 billion gallons, and the Wachusett Reservoir, holding 65 billion, supplying about 200 million gallons a day to 53 communities and more than 2.5 million people, with the Ware River as a supplemental source. The 400-square-mile watersheds are more than 86 percent forest and wetland. · At the John J. Carroll Water Treatment Plant in Marlborough, operating since 2005: ozone made from pure oxygen as the primary disinfectant, then ultraviolet light, fluoride, pH and alkalinity adjustment with sodium carbonate and carbon dioxide for corrosion control, and monochloramine for the distribution residual. The plant runs two separate parallel flow paths for redundancy. · No softening step. |
Not in the report: corrosion index.
SOURCE · MWRA Monthly Water Quality Analysis, July 2026, Carroll Water Treatment Plant finished water tap, read with the 2025 Annual Water Quality Test Results (mwra.com) · How we source these numbers
When a wash holds
What sets the cleaning clock
Winter dominates and it does so twice over. Road salt and grit coat low glazing and basement-level windows from the first treatment through the final thaw, and the freeze itself closes outdoor work for stretches rather than merely slowing it. Spring is consequently the heaviest single clean of the year across the whole city. Harbour salt is a constant on the waterfront regardless of season. Summer is the productive window and the only period when a wash reliably holds.
MASSACHUSETTS SEASON BY SEASON →What's specific to Boston
Boston sits on one of the softest municipal supplies on this site and the authority behind it says so without hedging: hardness of 10 mg/L, less than one grain per gallon, against its own stated threshold of 75 mg/L for water that would count as hard. Nothing in that supply marks a pane. Tap is the final rinse and treated rinse equipment answers a question this city does not ask. The water is wholesale — Quabbin sixty-five miles west, Wachusett thirty-five, serving fifty-one communities at roughly two hundred million gallons a day — and soft enough to be corrosive, which is why sodium carbonate and carbon dioxide are dosed for corrosion control before chloramine goes in for the distribution residual. What governs the work instead is the building stock. Beacon Hill, Back Bay and the South End carry original glass in protected districts, Back Bay's projecting bays put difficult glazing at height with nowhere to stand, and the winter closes part of the year.
Boston's water is among the softest on this site and the supplier states it in plain language. The Massachusetts Water Resources Authority answers the hardness question directly: its water has a hardness of 10 mg/L, which it notes is less than one grain per gallon by older measures, and it offers 75 mg/L as the point above which water would be considered hard.
At 10 mg/L there is effectively nothing in the supply to leave on a pane. Tap water is the final rinse anywhere on this system, and deionised equipment has no function here whatsoever — this is the clearest case on this site for spending the money on technique instead.
The city does not treat its own water. It comes from the Quabbin Reservoir about sixty-five miles west of Boston and the Wachusett Reservoir about thirty-five miles west, with the Ware River adding to the supply at times, and it is distributed locally by the Boston Water and Sewer Commission.
That supply is wholesale to a whole region rather than to one city. The two reservoirs serve fifty-one communities and delivered around two hundred million gallons a day, so the same figure describes a large part of eastern Massachusetts rather than Boston alone.
Water that soft is chemically aggressive, and the treatment reflects it. After disinfection the authority adjusts pH and alkalinity for corrosion control by adding sodium carbonate and carbon dioxide, specifically to hold down lead and copper leaching from home plumbing, then doses chloramine downstream to hold a residual through some six thousand miles of local mains.
Sodium is tested monthly and the highest level found has been in the mid-to-high thirties of milligrams per litre, which the supplier notes the Food and Drug Administration would classify as very low sodium. There is very little dissolved anything in this water.
With the mineral question closed, the Boston job is defined entirely by fabric and weather. The building stock is among the oldest in the country and much of it is in protected historic districts, which constrains method far more tightly than any water chemistry would.
How old the glass is
- Before 1940 · 47%wood sash and older glass
- 1940–1959 · 12%steel casements, early aluminium
- 1960–1979 · 14%aluminium sliders, often single-pane
- 1980–1999 · 10%double-pane units become standard
- 2000–2009 · 7%vinyl frames, low-E spreading
- 2010 or later · 11%low-E common: gentle cleaners only
The city, by neighborhood
What window cleaning costs in Boston
Access dominates: bow fronts, narrow lanes that exclude equipment, and protected frontage that restricts what can be set up on the public way all add time before any glass is touched. Historic-district work carries a genuine skill premium. A short season concentrates demand into spring and summer and firms pricing in exactly those months. No part of a Boston quote should be paying for treated rinse water.
Doing it yourself
The limiting factor here is almost never the water and almost always the building. Back Bay and South End bow fronts put glazing several storeys up over pavement with no safe ladder position, which is a professional job on access grounds alone. Original wavy glass in the historic districts is thin, irregular and irreplaceable, and it does not tolerate a scraper. Ground-floor and garden-level work in the outer neighbourhoods is perfectly reasonable for a homeowner in the warm months.
OPEN COST ESTIMATOR →2025 annual mean at the Dudley Square Roxbury monitor, Harrison AVE, 5.4 km west of the city (EPA site 25-025-0042).
2025 annual mean at the VON Hillern ST monitor, 19 VON Hillern ST, 3.4 km south-west of the city (EPA site 25-025-0044).
Largest air release: Duncan Galvanizing Corp., 69 Norman ST (fabricated metals), 1.2 km outside the city limits, 13,213 lb in 2024.
The Boston Water and Sewer Commission's water regulations set no limits on hose use, outdoor washing or watering days; they deal with service connections, meters, cross-connections and backflow protection.
Boston Water and Sewer Commission, water distribution system regulations · checked September 2026
Boston Water and Sewer Commission rules bar anyone from discharging, directly or indirectly, any water that is not entirely stormwater into a building storm drain or a Commission storm drain, except where the rules allow it, and a non-stormwater discharge needs a Drainage Discharge Permit first. Soapy wash water from cleaning glass should be kept out of the catch basins.
Boston Water and Sewer Commission, regulations governing sewers and storm drains · checked September 2026
Any change to a Boston landmark or to a building in one of the city's historic districts is reviewed and approved by the Boston Landmarks Commission or that district's commission, each supported by Landmarks staff. Applications are filed online, and a planner decides whether the work qualifies for expedited approval.
City of Boston, Landmarks Commission common questions · checked September 2026
What actually shows up on Boston glass
MassDOT and the municipal road commissions apply heavy salt loads to keep the state's narrow secondary roads passable through the winter. Salt aerosol on ground-floor glass within a quarter-mile of any plowed road is the dominant winter contamination pattern, and slush splatter from passing traffic coats the lower third of ground-floor glass on road-facing exposures. The post-winter call drives the entire residential spring schedule from the first week of April through the second week of May.
Boston, answered
How hard is the water in Boston, Massachusetts?＋
Boston runs on Boston Water and Sewer Commission, supplied by the Massachusetts Water Resources Authority lake or reservoir surface water at a published 10 mg/L (CaCO₃) — soft — less than one grain per gallon, in the supplier's own words.
How much does window cleaning cost in Boston?＋
Residential window cleaning in Boston typically runs $13–19 per pane or $380–620 for a standard single-story exterior. Access dominates: bow fronts, narrow lanes that exclude equipment, and protected frontage that restricts what can be set up on the public way all add time before any glass is touched.
When is the best time of year to clean windows in Boston?＋
Boston's drier, frost-free months are July to October, by NOAA's 1991–2020 normals for the Boston Logan International Airport station, where December brings the most rain. The calendar on this page marks July (after the May 4 bloom) and October (after smoke season and before frost). Frost nights usually run from November 9 to April 4.
Can I rinse windows with Boston tap water?＋
Yes, if the rinse is squeegeed off before it dries: Boston Water and Sewer Commission, supplied by the Massachusetts Water Resources Authority publishes dissolved solids of 114 mg/L, between this site's two dissolved-solids flags. Treatment starts with at the John J.
Why do my windows look dirty so quickly in Boston?＋
In Boston the dominant residue patterns include extremely soft supply at 10 mg/l, under one grain per gallon in the supplier's own terms and water soft enough to be aggressive, corrected with sodium carbonate and carbon dioxide for corrosion control. Winter dominates and it does so twice over.
Do I need a professional to clean my windows in Boston?＋
The limiting factor here is almost never the water and almost always the building. Back Bay and South End bow fronts put glazing several storeys up over pavement with no safe ladder position, which is a professional job on access grounds alone. Original wavy glass in the historic districts is thin, irregular and irreplaceable, and it does not tolerate a scraper.
What sets Beacon Hill apart for window cleaning in Boston?＋
Federal and Greek Revival townhouses on gaslit brick streets, with original wavy glass surviving in many sash and strict historic-district control over anything visible from the public way. Back Bay and The South End have their own housing stock and glazing as well.
Other cities we cover in Massachusetts
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Just over the Massachusetts line