Concord's surface supply is very soft at 9 to 10 mg/L, so glass trouble comes from the New England pollen wave and from snow and ice damage instead.
Concord's water averages 9.4 mg/L, some of the softest municipal supply in the country, so mineral spots barely register; the finish is lost to soap film and organic residue instead, which makes a thorough rinse matter more than a pure one. Spring pollen and winter snow and ice damage fill the rest of the calendar. August and September are the dependable months, the drive between clusters of homes figures in the price, and a single-story exterior runs $230 to $390.
The city's 2025 report puts hardness at 9.4 mg/L on average, between 9 and 10 — some of the softest municipal water in the country — meaning there is almost no mineral in Penacook Lake water to dry onto glass at all.
Figures by source, as reported.
| Hardness | 9–10 mg/L as CaCO₃ Averaging 9.4 mg/L; soft, as published by Concord General Services. |
|---|---|
| pH | 9.22 (range 8.62–9.6) |
| Alkalinity | 31 mg/L as CaCO₃ (range 28–33) |
| Manganese | 0.012 mg/L (range 0.005–0.026) |
| Sodium | 28.5 mg/L (range 26.2–30.3) |
| Chloride | 29 mg/L (range 27–30) |
| Disinfectant | chloramine |
| Source and treatment | Penacook Lake, a protected 362-acre surface source, with transfers from the Contoocook River when the watershed cannot meet demand and a backup well in Pembroke · Granular activated carbon, pre pH adjustment, rapid mix, flocculation, sedimentation and rapid sand filtration, chlorination with chloramines as the residual, fluoridation and post pH adjustment · No softening step. |
Not in the report: corrosion index, iron and total dissolved solids.
SOURCE · City of Concord 2026 Annual Water Quality Report (2025 data), Water Quality Parameters 2025 table (printed as an image) · How we source these numbers
With granite grit washing off sills every freeze-thaw, the wash that holds in Concord is the one timed after the last hard frost.
NEW HAMPSHIRE SEASON BY SEASON →Concord has some of the softest municipal water in the country, and that single fact reorganises the job here: mineral spotting is barely a factor, while soap film and organic residue are the things that actually ruin a finished pane. The city is also a granite town with a mill village attached to its north end, so the glass ranges from 1820s public architecture to 1980s subdivision sash.
Penacook Lake has supplied Concord since 1872 and the city owns the whole 2,500-acre watershed around it. Recreation has been banned on the lake since 1951 — it is the only lake in New Hampshire that bars public access outright to protect a drinking supply — and the raw water is rated Class A as a result.
The finished water leaving the Hutchins Street plant is reported at 9.4 mg/L hardness on average in 2025, between 9 and 10, with calcium at 3.8 mg/L. In practical terms there is almost no mineral left in it to dry onto a pane, which is why rinse water here sheets off clean on elevations that would spot badly in a hard-water city.
Softness moves the problem rather than removing it. With so little calcium to break surfactants, detergent rinses poorly and leaves a faint film that catches low sun, so the usual local failure is too much soap in the bucket rather than too little.
The plant finishes with chloramine rather than free chlorine and lifts distribution pH to around 9. Alkaline, low-mineral water is easy on glass but unforgiving of dwell time on painted and anodised frames, so runoff gets wiped off the sill rather than left to dry.
In dry spells the lake cannot keep up with demand and the city pumps in Contoocook River water, with the Sanders Station wells in Pembroke held as emergency backup. Late-summer supply therefore carries more river character than the spring supply does, and the water can run slightly dirtier without any change in hardness.
Downtown is a granite district in the literal sense: the State House and much of the civic core were built from stone quarried on the city's own ridges, and granite sills and surrounds shed grit onto the glass below them every freeze-thaw cycle.
Penacook, at the north end, is a separate 19th-century mill village on the Contoocook rather than a suburb, and its housing and storefront glazing are a generation older than the subdivisions along the city's southern approaches.
Central New Hampshire is colder than the Seacoast and exterior work effectively stops from December into February. The book here is compressed into spring and autumn, which makes route density and scheduling — not glass count — the thing that decides whether a residential job is worth the drive.
Concord pricing turns on the compressed spring-and-autumn season and the drive between clusters, not on pane count.
Soft water makes over-soaping the standard local mistake, and the State House district's heritage glazing is not a first-timer's job.
OPEN COST ESTIMATOR →Nearest EPA particle monitor: 33 km
Largest air release: Kalwall Corp Flat Shee T DIV, 168 River RD (plastics and rubber), 1.3 km outside the city limits, 2,450 lb in 2024.
Concord has no standing hose or watering schedule; instead its Director of Waterworks may declare an emergency and impose use restrictions the day they are published in the paper. Limits on commercial water use, a cleaning crew's included, apply only when the director finds reserves pose an immediate threat to health and safety.
Concord Code 9-2-3: the waterworks director's emergency declaration · checked September 2026
Concord's public-health chapter forbids placing or leaving wastewater, dirt, soot, rubbish or other refuse in or near any street, alley or public place, or in a pond or other still water, so a crew's spent bucket water can't be tipped at the kerb.
Concord Code 13-1-1: rubbish and refuse that are menaces to the public health · checked September 2026
Inside Concord's Historic (HI) overlay, any work that changes the exterior appearance of a building and can be seen from a street needs a Certificate of Approval from the Heritage Commission before it starts. Swapping visible windows falls under that rule; glass hidden from the street does not.
Concord Code 28-3-4: HI District and the Heritage Commission's Certificate of Approval · checked September 2026
Late-winter and early-spring ice-melt residue carries chloride-residue, mineral residue, and organic residue composite. Ice-dam meltwater residue from roof-edge ice damming produces a distinctive composite residue on upper-pane and sash-perimeter glass. Percarbonate-citric ladder protocol required on the worst-affected stock.
The city's 2025 report puts hardness at 9.4 mg/L on average, between 9 and 10 — some of the softest municipal water in the country — meaning there is almost no mineral in Penacook Lake water to dry onto glass at all.
Residential window cleaning in Concord typically runs $8–12 per pane or $230–390 for a standard single-story exterior. Concord pricing turns on the compressed spring-and-autumn season and the drive between clusters, not on pane count.
Concord's drier, frost-free months are August and September, by NOAA's 1991–2020 normals for the Concord Municipal Airport station, where June brings the most rain. The calendar on this page marks August (after the May 15 bloom and after smoke season). Frost nights usually run from October 3 to May 8.
Usually yes: Concord General Services publishes hardness of 9–10 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: sodium up to 28.5 mg/L). It draws on Penacook Lake, a protected 362-acre surface source.
In Concord the dominant residue patterns include new england pollen wave and snow and ice damage. With granite grit washing off sills every freeze-thaw, the wash that holds in Concord is the one timed after the last hard frost.
Soft water makes over-soaping the standard local mistake, and the State House district's heritage glazing is not a first-timer's job.
Government and commercial core around the State House: granite public buildings, tall 19th-century storefront glass, and upper-floor sash on brick blocks. Street-level access is good, but the granite detailing above the glass keeps depositing grit on it. East Concord and Penacook have their own housing stock and glazing as well.
Just over the New Hampshire line