Dover glass under the air base approach paths collects aircraft exhaust particulate, farms add seasonal field dust, and water runs 23 to 127 mg/L hard.
Dover's wells vary so much that its own report puts hardness anywhere from 23 to 127 mg/L, soft at one well and hard at another, so find out which serves the house before choosing a rinse. Homes under the air base approach paths collect exhaust particulate from heavy transport aircraft, and farms add seasonal field dust. July to October is the best stretch; state government, the university and the base keep contract crews busy, and a single-story exterior runs $220 to $380.
The city's 2024 report prints total hardness from 23.0 to 126.6 mg/L across the year — soft at the bottom of that range and hard at the top — so two Dover addresses can be on noticeably different water depending on which wells feed them. The report's average column repeats the 23.0 minimum, which cannot be the true centre of that spread, so no single city figure is used here. Alkalinity in the same table runs from 69 to 333 mg/L. In practice mineral spotting is a real problem on some streets and barely one on others, and a test pane on any large recurring account settles which.
| Hardness | 23–127 mg/L as CaCO₃ Soft at the low end, hard at the high, as published by City of Dover. |
|---|---|
| pH | 7.8 (range 6.8–8.2) |
| Alkalinity | 202.3 mg/L as CaCO₃ (range 69.4–332.9) |
| Manganese | 0.0314 mg/L (range 0–0.1088) |
| Sodium | 65 mg/L (range 12–162.5) |
| Chloride | 10.3 mg/L (range 4.7–43.4) |
| Total dissolved solids | 275.1 mg/L (range 174–406) |
| Disinfectant | free chlorine |
| Source and treatment | Groundwater, per the EPA SDWIS federal record · Greensand filtration for iron and manganese, granular activated carbon for taste and odour, pre and post chlorination, fluoridation, with pre and post pH adjustment for corrosion control · No softening step. |
Not in the report: corrosion index and iron.
SOURCE · City of Dover 2024 Drinking Water Quality Report, Delaware Secondary Standards test results (replaces the state Office of Drinking Water 2023 supplement used earlier, since the city's own newer report carries the fuller mineral table) · How we source these numbers
Two unrelated cycles overlap. Agricultural dust arrives in short heavy bursts at land preparation and harvest, and servicing a fringe property in the middle of one is wasted effort. Aircraft film accumulates steadily and independently of season on the properties under the flight paths, which want a shorter regular interval. Coastal humidity keeps mildew active on shaded elevations from late spring through autumn, and the winter is mild enough that the working year is longer here than anywhere north of it.
DELAWARE SEASON BY SEASON →Dover is a groundwater city in a state whose northern cities are not, and its own 2024 report shows what that means: hardness anywhere from 23 to 127 mg/L depending on the well, where Wilmington's two river plants average 136 and 154. The distinctive airborne factor is the air base: heavy transport aircraft on repeated circuits leave an oily exhaust film on properties under the approach paths that a plain-water method will not shift. Beyond that it is farmland dust, coastal humidity and a small but genuinely early colonial core.
Dover draws groundwater rather than surface water, which puts it in a different category from the northern Delaware cities and is the likely reason it reads differently in every comparison available.
The city's own 2024 report puts total hardness anywhere between 23 and 127 mg/L, so the single figure of 64 often quoted for Dover hides a spread running from soft to hard.
That spread is the practical point: test a pane on each large account rather than trusting a city average. And against Wilmington's river plants, which average 136 and 154, the common assumption that a whole state shares one water character is clearly wrong over a distance of less than fifty miles.
Aircraft operations from the air base are a genuine and unusual airborne factor. Heavy transport aircraft on repeated circuits put exhaust particulate into the air over the surrounding area in a way ordinary civil aviation does not.
That particulate is oily rather than mineral, and it forms a film that resists a plain-water method. Properties on the approach and departure paths need a detergent step that the rest of the town does not.
Kent County farmland begins almost immediately outside the built-up area, so agricultural dust arrives in concentrated bursts at land preparation and harvest rather than accumulating steadily.
The colonial core is small but genuinely old, and the buildings around the green carry early glazing that has survived because the town stayed small for a long time. Era identification matters before any scraper comes out.
Coastal plain humidity keeps shaded elevations damp through a long summer, which makes mildew in frames and glazing channels a routine complaint rather than an occasional one.
The state government and the university together give this small city an unusually institutional client base, which means procurement processes and scheduled contracts rather than the ad-hoc residential work a town this size would otherwise support.
The institutional client base is the defining commercial feature of this market — state government, the university and the base economy together support scheduled contract work that a city of this size would not otherwise generate, and that work prices on reliability and process compliance. Residential pricing splits between efficient west-side routes and long drives to the agricultural fringe. Properties under the flight paths justify a shorter interval, and pricing them annually underestimates the condition they reach.
Modern residential glass in west Dover is easy work and the supply, whatever the exact figure, is not the difficulty. The two things that reward professional handling are the oily aircraft film, which needs a detergent and dwell time rather than more scrubbing, and the early glazing around the green, which is genuinely old and will not survive a confident scraper. Institutional work at the capital complex and the university involves access processes rather than technical difficulty.
OPEN COST ESTIMATOR →2025 annual mean at the Platform in Field Behind Delaware FED. Credit Union Bldg monitor, Water ST. Dover, 0.6 km south-east of the city (EPA site 10-001-0003).
Largest air release: Garrison Energy Center, 450 Garrison OAK DR (electric utilities), inside the city limits, 2,892 lb in 2024.
When Dover's water supply faces an emergency, the city manager orders public water users to limit or stop sprinkling streets, grass and other vegetation.
Dover Code §110-64: sprinkling limitation · checked September 2026
It is unlawful in Dover to throw, place or deposit any article, object or substance into a storm sewer or its inlets, to attempt it, or to have it done.
Dover Code §98-164: prohibited discharges into system · checked September 2026
Dover's historic district commission helps the planning commission and city planner review applications for architectural review certification of work in its historic district.
Dover Zoning Ordinance, Article 10 §3: historic district commission and architectural review · checked September 2026
Wet-only handling. Peak mid-April. Pollen lifts cleanly with water plus light alkaline soap; do not scrape.
Crop dust and residual spray deposit on east-facing residential glass east of Dover toward Bombay Hook. Wet-rinse-first then standard wash.
The city's 2024 report prints total hardness from 23.0 to 126.6 mg/L across the year — soft at the bottom of that range and hard at the top — so two Dover addresses can be on noticeably different water depending on which wells feed them. The report's average column repeats the 23.0 minimum, which cannot be the true centre of that spread, so no single city figure is used here.
Residential window cleaning in Dover typically runs $7–12 per pane or $220–380 for a standard single-story exterior; Kent County had 47 janitorial and window-cleaning businesses in the Census Bureau's 2023 County Business Patterns.
Dover's drier, frost-free months are July to October, by NOAA's 1991–2020 normals for the Dover station, where April brings the most rain. The calendar on this page marks July (after the April 18 bloom) and October (after smoke season and before frost). Frost nights usually run from November 4 to April 4.
Yes, if the rinse is squeegeed off before it dries: City of Dover publishes dissolved solids of 275.1 mg/L, between this site's two dissolved-solids flags. Its sodium, up to 65 mg/L, leaves a salt film that pulls moisture back, so rinse it off rather than let it dry. Treatment starts with greensand filtration for iron, manganese, granular activated carbon for taste and odour.
In Dover the dominant residue patterns include aircraft exhaust particulate on the base approach paths and agricultural field dust in seasonal bursts. Two unrelated cycles overlap. Agricultural dust arrives in short heavy bursts at land preparation and harvest, and servicing a fringe property in the middle of one is wasted effort.
Modern residential glass in west Dover is easy work and the supply, whatever the exact figure, is not the difficulty. The two things that reward professional handling are the oily aircraft film, which needs a detergent and dwell time rather than more scrubbing, and the early glazing around the green, which is genuinely old and will not survive a confident scraper.
The colonial civic core, with early public buildings around a historic green and the state's legislative complex beside it. Institutional scheduling, security arrangements and conservation-grade handling on the oldest fabric. Loockerman Street and Dover Air Force Base surrounds have their own housing stock and glazing as well.
Just over the Delaware line