Yonkers buys New York City water at 31 to 120 mg/L hard, and north-facing glass near the Metro-North line collects diesel particulate year-round.
Yonkers buys New York City's water, almost all of it the soft Catskill and Delaware supply, so tap water dries nearly clean. North-facing glass near the Metro-North line collects diesel film year-round, which is easy to mistake for ordinary grime, and August to October is the best stretch to wash. Steep streets add setup time in parts of the city, and a single-story exterior runs $320 to $540.
Yonkers drinks New York City's water, and about 97% of it is Catskill and Delaware supply — the soft end of DEP's published range rather than the Croton-blended upper end. In practice that means one of the least mineralised supplies on the eastern seaboard: tap water rinses dry clean here, and spotting complaints almost always turn out to be road salt or failing putty rather than hardness.
| Hardness | 31–120 mg/L as CaCO₃ Soft to slightly hard on the Catskill/Delaware water that supplies about 97% of the city, rising toward moderately hard only in the small Croton-blended share, as published by City of Yonkers Water Bureau (purchased NYC DEP supply, with Westchester County Water District #1). |
|---|---|
| pH | 7.3 (range 6.9–8.1) |
| Alkalinity | 25 mg/L as CaCO₃ (range 16–72) |
| Corrosion index | Langelier index -2.13 (range -2.75 to -1.08) — undersaturated: this water dissolves scale rather than depositing it |
| Iron | 0.027 mg/L (range 0–0.095) |
| Manganese | 0.021 mg/L (range 0–0.14) |
| Sodium | 16 mg/L (range 9–49) |
| Chloride | 19 mg/L (range 12–72) |
| Total dissolved solids | 73 mg/L (range 45–240) |
| Disinfectant | uv + chlorine |
| Source and treatment | Three systems: the Croton, Catskill and Delaware. In non-drought periods Croton provides about 10 percent of daily supply and the Catskill/Delaware supply the rest. The Catskill/Delaware water is unfiltered, operating under a federal Filtration Avoidance Determination. · Catskill/Delaware: chlorine, then ultraviolet disinfection, then food-grade phosphoric acid to form a protective pipe coating, sodium hydroxide to raise pH against corrosion, and fluoride at 0.7 mg/L. Croton: treated at the Croton Water Filtration Plant, an underground facility in the Bronx rated 290 million gallons a day, by coagulation, dissolved air flotation, filtration and disinfection. · No softening step. |
SOURCE · New York City Department of Environmental Protection, 2025 Drinking Water Supply and Quality Report, 'Detected Conventional Physical and Chemical Parameters' table and the treatment sections (nyc.gov/assets/dep). Yonkers' own annual water quality report states the city obtains its drinking water from the New York City Water Supply System, and publishes no independent figures. · How we source these numbers
Two mechanical clocks dominate and neither is seasonal in the ordinary sense. Metro-North diesel particulate settles on north-facing glass within about half a mile of the line and reloads on the timetable rather than the weather. Road salt then runs on the treatment cycle from November through March. Both reload independently of how clean the glass was left, which is why intervals here should be set by exposure rather than by calendar.
NEW YORK SEASON BY SEASON →Yonkers buys New York City water — about 97% Catskill/Delaware, unfiltered, treated at Kensico with chlorine and ultraviolet light — so it sits at the soft end of the range DEP publishes for the whole system, and the Croton upper bound describes almost none of the city. The retail operator is the City of Yonkers Water Bureau, taking purchased NYC DEP supply alongside water from Westchester County Water District #1. With hardness effectively off the table, the local problems are mechanical: Metro-North diesel film near the line, winter road salt, failing pre-war putty lines and steep hillside access.
Yonkers does not have its own source. The city buys New York City water — Catskill and Delaware aqueduct supply blended at Kensico Reservoir — and takes a smaller share through Westchester County Water District #1. NYC's own Hillview Reservoir sits inside the city, which is why water enters the Yonkers system at several points before it reaches the boroughs.
About 97% of what Yonkers receives is Catskill/Delaware water, with roughly 3% Croton. That matters because the city sits at the soft end of the range New York City publishes for its whole system — the harder Croton-blend figure describes almost none of Yonkers.
This is unfiltered surface water, one of only a handful of large supplies in the country permitted to operate without filtration. It is treated at Kensico with chlorine and ultraviolet light rather than filtered, which keeps the mineral content low and means the supply's quality depends on watershed protection rather than on a treatment train.
Metro-North diesel particulate is the signature local loading. Within about half a mile of the line, north-facing glass picks up an oily film on the timetable rather than the weather, and a detergent chosen for spotting will spread it rather than lift it.
Park Hill and Lawrence Park West carry substantial pre-war housing with original glazing, and a century of Hudson Valley freeze-thaw has worked those putty lines hard. Gentle pressure and pure-water systems are competitive standards there, not because of the water but because of the joints.
The city drops steeply from the ridges to the Hudson, and hillside streets make ladder footing and equipment placement a real time cost. A quote built from pane count without seeing the approach will be short on a large share of the residential book.
Proximity to the Metro-North corridor is the clearest driver of frequency and the least understood by customers, who tend to read diesel film as general grime. Beyond that, the city's steep topography down to the Hudson means access and ladder footing consume time on a large share of residential jobs, and quoting from a floor plan rather than a site visit under-prices the hillside streets.
Soft water and accessible housing make most of the work genuinely approachable. The exception is the pre-war stock in Park Hill and Lawrence Park West, where original glazing sits in putty lines that have been through a century of Hudson Valley freeze-thaw. Once those joints are soft, pressure of any kind drives water behind the glass, and the repair costs more than years of cleaning.
OPEN COST ESTIMATOR →2025 annual mean at the IS 52 monitor, IS 52 681 Kelly ST, 14.7 km south of the city (EPA site 36-005-0110).
2025 annual mean at the Pfizer LAB Site monitor, 200TH Street and Southern Bouldvard Pfizer Lab, 8.7 km south of the city (EPA site 36-005-0133).
Largest air release: Electronic Devices Inc., 21 Gray Oaks AVE (computers and electronic products), inside the city limits, 510 lb in 2024.
Yonkers's mayor and public works commissioner can declare a public emergency to preserve the city's water supply when they judge the city's health, safety and welfare call for it.
Yonkers Code §95-3: water emergencies · checked September 2026
Yonkers prohibits discharging anything other than stormwater into its municipal storm sewer system, and starting or continuing an illegal discharge there, apart from listed exempt flows the city has not found to be substantial polluters.
Yonkers Code §96-44: discharge prohibitions; exemptions; illicit connections · checked September 2026
No alteration or repair that materially changes the appearance of a feature of a Yonkers landmark or historic district property may begin without a certificate of appropriateness, whatever other permits it holds.
Yonkers Code §45-8: certificate of appropriateness · checked September 2026
Heavy road salting from December through March produces an aerosolized salt mist that bonds to ground-floor glass and corrodes aluminum and steel sash hardware over time. The salt film cleans off but the underlying frame damage is cumulative. Worst in NYC, Long Island, and the snow belt.
The pre-1945 wood-sash housing stock in NYC, Westchester, and the older upstate cities is reaching the end of its original glazing putty service life. The putty crumbles around the perimeter of the pane and produces a chalky residue on the lower edge of the glass that cleaning does not solve. Documentation and a glazier referral are the right move.
Yonkers runs on City of Yonkers Water Bureau (purchased NYC DEP supply, with Westchester County Water District #1) lake or reservoir surface water at a published 31–120 mg/L (CaCO₃) — soft to slightly hard on the Catskill/Delaware water that supplies about 97% of the city, rising toward moderately hard only in the small Croton-blended share.
Residential window cleaning in Yonkers typically runs $11–16 per pane or $320–540 for a standard single-story exterior. Proximity to the Metro-North corridor is the clearest driver of frequency and the least understood by customers, who tend to read diesel film as general grime.
Yonkers's drier, frost-free months are August to October, by NOAA's 1991–2020 normals for the Dobbs Ferry-Ardsley station, where April brings the most rain. The calendar on this page marks August (after the April 26 bloom) and October (after smoke season and before frost). Frost nights usually run from October 26 to April 20.
Usually yes: City of Yonkers Water Bureau (purchased NYC DEP supply, with Westchester County Water District #1) publishes dissolved solids of 73 mg/L, low enough that tap-rinsed glass tends to dry clean. Iron, manganese, sodium and chloride all sit under this site's flags (highest: manganese up to 0.021 mg/L). It draws on three systems: the Croton, Catskill and Delaware.
In Yonkers the dominant residue patterns include metro-north diesel particulate on north-facing glass near the line and winter road-salt aerosol on lower panes, november to march. Two mechanical clocks dominate and neither is seasonal in the ordinary sense.
Soft water and accessible housing make most of the work genuinely approachable. The exception is the pre-war stock in Park Hill and Lawrence Park West, where original glazing sits in putty lines that have been through a century of Hudson Valley freeze-thaw.
Mid-rise commercial core; revitalized waterfront with substantial fixed glazing. Park Hill and Bryn Mawr Park have their own housing stock and glazing as well.
Just over the New York line