Alexandria's Old Town still has irreplaceable period cylinder and crown glass, and its locally treated Potomac water runs 78 to 191 mg/L by season.
Alexandria's Potomac water, treated at its own plant, runs from moderately hard to very hard with the seasons, so glass that dries clean one month may spot the next. Old Town still has irreplaceable cylinder and crown glass that needs slow, careful work, and April and August to October are the best months. That careful time is the product in Old Town, while a typical single-story exterior runs $350 to $600.
Virginia American Water's 2025 report gives Alexandria's total hardness as 78 to 191 mg/L, from moderately hard to very hard. The city is served by its own investor-owned operator treating Potomac water at its own plant, which makes it a different finished supply from the federally treated water in the adjacent county — so the neighbour's number will not transfer here. The source is a large river, which is why the operator's own span is so wide.
| Hardness | 78–191 mg/L as CaCO₃ The published span crosses from moderately hard through hard into very hard, so no single band label describes the city. |
|---|---|
| pH | 7.1–7.6 |
| Alkalinity | 41–120 mg/L as CaCO₃ |
| Iron | not detected |
| Manganese | not detected |
| Sodium | 13–34.9 mg/L |
| Disinfectant | chloramine |
| Source and treatment | A consecutive system: the Alexandria District buys finished water from two Fairfax Water surface plants — Corbalis on the Potomac River and Griffith at the Occoquan Reservoir — about 17 million gallons a day across the city's twenty ZIP codes · Virginia American Water operates no treatment plant in Alexandria. Fairfax Water treats upstream and the district distributes, holding a chloramine residual through the system. · No softening step. |
Not in the report: corrosion index, chloride and total dissolved solids.
SOURCE · Virginia American Water, Alexandria District 2025 Annual Water Quality Report, PWS 6510010 (amwater.com/ccr/alexandria.pdf), read with the district's Typical Water Quality Information sheet (amwater.com/twq/alexandria_twq.pdf) · How we source these numbers
Organic and pedestrian rather than mineral. Pollen through spring and sap through the growing season in the canopied neighbourhoods; continuous footfall soiling on Old Town and Del Ray shopfronts that reloads within weeks; river damp on the lowest waterfront elevations. The most durable residential wash is late spring, once the canopy has finished dropping.
VIRGINIA SEASON BY SEASON →Alexandria holds glass older than the technology this trade assumes. Old Town retains period glazing in quantity, including early cylinder and crown glass — uneven in surface, variable in thickness across a single pane, and not replaceable like for like. It is softer than float glass, rarely flat, and traps detergent at the edges, so blades are out, pressure goes lighter than instinct suggests, and the perimeter detailing takes longer than the pane. The putty is usually the more fragile element: a century-old compound has lost its oils and cracks loose under force a modern sash ignores. On water, the city is served by an investor-owned operator treating Potomac water locally — distinct from the federally treated supply next door despite sitting on the same river — so a figure cannot be borrowed across that boundary, and the operator's own 2025 report gives Alexandria 78 to 191 mg/L.
Alexandria holds glass that predates the technology most of this trade is built around, and that is not a curiosity — it is a handling instruction. Old Town's eighteenth and nineteenth-century buildings retain period glazing in quantity, including early cylinder and crown glass whose surfaces are uneven, whose thickness varies across a single pane, and which cannot be replaced like for like if it is damaged.
Period glass behaves differently under a squeegee and it is worth saying how. It is softer than modern float glass, it is rarely flat, and its irregularities trap and hold detergent at the edges — so a blade is out of the question, pressure has to be lighter than feels natural, and the detailing at the perimeter takes longer than the pane itself.
The putty is usually more fragile than the glass. Glazing compound that has been in place for a century or more has lost its oils and become brittle, and the force that a modern sash shrugs off is enough to crack it loose — which turns a wash into a repair the client did not ask for.
The utility here is an investor-owned operator drawing from the Potomac and treating it locally, which makes Alexandria's supply distinct from the federally treated water serving the county to the north despite the two sitting side by side on the same river.
That distinction matters because it means a figure cannot be borrowed across the boundary. Two adjacent jurisdictions on the same river with different operators and different plants will not have identical finished water, and this operator's own 2025 report puts Alexandria's hardness at 78 to 191 mg/L.
A river supply varies with flow and season in any case, so a single point value from this system would describe a moment rather than a constant — which is the same caution that applies to every river city on this site and is worth repeating where the neighbour's water is close enough to be confused with it.
Old Town's commercial frontage is judged to a preservation-district standard by a client base that chose the district deliberately. Shopfront glass there is looked at closely and often, which raises the finishing requirement above what the pane count suggests and rewards crews who work slowly and visibly carefully.
Glazing age and irreplaceability drive Old Town, where the correct method is markedly slower and that time is the product rather than an overhead. Presentation standard drives the district's commercial frontage. Height and access drive the Carlyle corridor, which is a separate contracted trade from anything in the historic core.
West End and Rosemont stock is reasonable homeowner work. Old Town is the clearest case in this entire cohort for not attempting it yourself — the glass is irreplaceable, the putty fails without warning, and the damage is permanent and visible from the street in a district where that matters to neighbours as well as owners.
OPEN COST ESTIMATOR →2025 annual mean at the Lee District Park monitor, STA. 46-B9, LEE Park, Telegraph Road, 5.4 km south of the city (EPA site 51-059-0030).
2025 annual mean at the Aurora Hills Visitors Center monitor, S 18TH and Hayes ST, 4.8 km north-east of the city (EPA site 51-013-0020).
Largest air release: Allied Aviation Fueling Co Inc, Ronald Reagan National Airport (petroleum bulk terminals), 1.4 km outside the city limits, 1,266 lb in 2024.
Alexandria's city manager can declare a water shortage condition and must tell the public, setting out the voluntary restrictions that then apply. Commercial car wash installations must run a water recycling system the building official approves.
Alexandria City Code §5-6-6: declaration of water shortage condition · Alexandria City Code §8-1-18: water conservation · checked September 2026
Alexandria makes it unlawful to throw, drain or discharge anything but stormwater into the city's stormwater system, or to let people working under your control do it; a short list of exceptions covers things like water-line flushing and landscape irrigation. Detergent rinse from a storefront or window wash is not on that list, so it has to be caught or sent to a sanitary drain.
Alexandria City Code Sec. 11-13-2: illegal dumping prohibited · checked September 2026
Once Alexandria's board of architectural review approves an erection, reconstruction, alteration or restoration in a historic district, a dated certificate of appropriateness signed by the board's secretary is issued to the applicant.
Alexandria Zoning Ordinance §10-106: issuance and expiration of certificates of appropriateness · checked September 2026
Late-summer low-flow stretches concentrate dissolved solids in the Potomac supply. Citric prerinse with extended dwell (3-4 minutes) handles the calcium-carbonate-plus-organic composite.
Pine, oak, and grass pollen wave through the metro and the Piedmont. Standard wet-only handling.
Virginia American Water's 2025 report gives Alexandria's total hardness as 78 to 191 mg/L, from moderately hard to very hard. The city is served by its own investor-owned operator treating Potomac water at its own plant, which makes it a different finished supply from the federally treated water in the adjacent county — so the neighbour's number will not transfer here.
Residential window cleaning in Alexandria typically runs $12–18 per pane or $350–600 for a standard single-story exterior. Glazing age and irreplaceability drive Old Town, where the correct method is markedly slower and that time is the product rather than an overhead.
Alexandria's drier, frost-free months are April and August to October, by NOAA's 1991–2020 normals for the Washington Reagan Airport station, where May brings the most rain. The calendar on this page marks August (after the April 11 bloom), September (after smoke season) and October (before frost). Frost nights usually run from November 18 to March 24.
Not as the final rinse: Virginia American Water (Alexandria) publishes hardness of 78–191 mg/L, enough to spot as it dries, so finish with pure water. Water left to dry leaves mineral scale; fresh spots lift with a mild acid. It draws on a consecutive system: the Alexandria District buys finished water.
In Alexandria the dominant residue patterns include locally treated potomac river supply, seasonally variable and distinct from the neighbouring federal system — no figure read here and irreplaceable period cylinder and crown glass across the old town district. Organic and pedestrian rather than mineral.
West End and Rosemont stock is reasonable homeowner work. Old Town is the clearest case in this entire cohort for not attempting it yourself — the glass is irreplaceable, the putty fails without warning, and the damage is permanent and visible from the street in a district where that matters to neighbours as well as owners.
One of the largest and most complete eighteenth and nineteenth-century districts in the country. Genuine period glazing survives in quantity here, including early cylinder and crown glass in the oldest buildings — assume irreplaceable until proven otherwise. Del Ray and Rosemont have their own housing stock and glazing as well.
Just over the Virginia line