Window Washing in San Antonio
San Antonio's groundwater is extremely hard at 257 to 342 mg/L, so irrigation overspray etches glass, and mountain cedar pollen hits from December to February.
San Antonio's groundwater is extremely hard, strong enough that repeated sprinkler overspray etches glass rather than just spotting it, so keep irrigation off the windows and finish with a pure-water rinse. Mountain cedar pollen coats glass through the winter; the best washing months are February, April, July, August and November. Treated rinse water is a real line item here, part of why a single-story exterior runs $300 to $510.
What the water means for the glass
Fifteen to twenty grains is the top of the scale, and at that concentration water stops being something that spots glass and becomes something that damages it. The distinction matters commercially: spotting is a cleaning problem, etching is a replacement problem, and in San Antonio the second one is real on any pane that takes repeated irrigation overspray.
San Antonio tap water, by the numbers
| Hardness | 257–342 mg/L as CaCO₃ 15 to 20 grains per gallon in the utility's own words — very hard across the whole span, as published by San Antonio Water System. |
|---|---|
| Disinfectant | free chlorine |
| Source and treatment | Purchased and local supply, per the EPA SDWIS federal record · Coagulation, flocculation, sedimentation and rapid sand filtration, reverse osmosis for inorganics, pre and post chlorination and fluoridation · No softening step. |
Not in the report: pH, alkalinity, corrosion index, iron, manganese, sodium, chloride and total dissolved solids.
SOURCE · San Antonio Water System 2026 Water Quality Report · How we source these numbers
When a wash holds
What sets the cleaning clock
The supply is constant rather than seasonal, so the interval is set by exposure rather than by the calendar — irrigated elevations need attention on a far shorter cycle than sheltered ones on the same house. The one true seasonal event is the December-to-February cedar wave, which is the only time of year the air rather than the water dictates the schedule.
TEXAS SEASON BY SEASON →What's specific to San Antonio
SAWS states on its own site that typical hardness ranges from 15 to 20 grains per gallon — roughly 257 to 342 mg/L, very hard by any scale and among the hardest delivered water in any US major metro. Sprinkler overspray etches glass within months here, which makes aftercare and protective coatings a real subsegment rather than an upsell. Cedar pollen in midwinter and Hill Country limestone dust do the rest.
SAWS publishes the figure as a range in grains rather than a point in milligrams: typical hardness runs 15 to 20 grains per gallon, about 257 to 342 mg/L. The utility attributes it to naturally occurring calcium carbonate in the Edwards and Trinity aquifers, and it is candid that this is simply what the rock gives — there is no softening step and none is planned.
The Edwards is a karst limestone aquifer, which is why the water is this hard and why the figure is stable rather than seasonal. Unlike a river city, San Antonio does not get a spring dilution — the mineral load is a property of the formation, so a method that works in March works in September.
At this hardness, sprinkler overspray is not a spotting problem, it is an etching problem. Repeated wet-dry cycles of 300-plus mg/L water on the same lower panes leave permanent surface damage within months, not years. Identifying and redirecting irrigation heads is genuinely part of the job here, and a crew that only cleans is treating a symptom.
That permanence changes the commercial conversation. Restoration and protective coating work has real demand in this market because glass genuinely gets destroyed, and a customer who has already lost a patio door understands why prevention costs money. Very few markets on this site support that argument honestly.
Deionised or filtered final rinse is not a premium here, it is the baseline for anything that matters. Tap rinsing on a sunny elevation at these concentrations will spot before the pane finishes drying, and in summer heat the window between wash and dry is very short.
Cedar pollen — mountain juniper — runs December through February and coats every surface in the region. It is a winter event rather than a spring one, which catches out crews used to a March calendar, and sashes and frames need a dedicated brush pass before any glass contact.
Hill Country limestone dust drifts in on west winds and is chemically the same material as the scale. It is fine, alkaline and abrasive, and working it dry grinds it across the glass — the combination of airborne limestone and dissolved limestone is what makes this a two-step market.
The historic core is unusually deep for a Sun Belt city. King William is pre-1900 Victorian with original wavy glass, Olmos Park is 1920s Mediterranean revival under preservation oversight, and the River Walk frontage downtown is tourist-corridor storefront judged on appearance daily.
How old the glass is
- Before 1940 · 5%wood sash and older glass
- 1940–1959 · 14%steel casements, early aluminium
- 1960–1979 · 23%aluminium sliders, often single-pane
- 1980–1999 · 27%double-pane units become standard
- 2000–2009 · 15%vinyl frames, low-E spreading
- 2010 or later · 15%low-E common: gentle cleaners only
The city, by neighborhood
What window cleaning costs in San Antonio
Water treatment is a real line item here and almost nowhere else on this site — filtered or deionised rinse is a cost of doing the job rather than an option. Irrigation exposure drives frequency, heat compresses the working day into its cooler ends, and restoration work on etched glass prices entirely separately from cleaning. Heritage handling in King William and Olmos Park sits on top of all of it.
Doing it yourself
A homeowner can wash glass in San Antonio; what they cannot easily do is stop it from being ruined. The damage here is cumulative and silent — overspray drying on the same lower panes week after week — and by the time it is visible it is etched rather than dirty. The genuine professional value is diagnostic: spotting the irrigation pattern, catching etching early, and knowing when a pane needs restoration rather than another wash.
OPEN COST ESTIMATOR →2024 annual mean at the San Antonio Bulverde Parkway monitor, 3843 Bulverde Parkway, 21.8 km north-east of the city (EPA site 48-029-1087).
2025 annual mean at the Old Hwy 90 monitor, 911 Old Hwy 90 West, 6.9 km south-west of the city (EPA site 48-029-0677).
Largest air release: Toyota Motor Manufacturing Texas, 1 Lone Star Pass (transportation equipment), inside the city limits, 113,391 lb in 2024.
SAWS counts any water running into a gutter, ditch or drain as waste at all times. Outside drought stages, driveways and sidewalks may be washed only without runoff, and the Edwards Aquifer drought stages tighten the rules further, so rinse glass by hand and keep the water on your own lot.
San Antonio Water System, Year-round watering rules · checked September 2026
San Antonio's code bans draining listed wastes into its storm sewer system or any street, gutter or ditch that feeds it, paint rinse water and carpet-cleaning waste among them, and its commentary names washing and cleaning materials as the dumping it targets. The rules are not aimed at non-contaminated, non-polluting water, so a plain rinse is treated differently from soapy wash water.
San Antonio Code §34-702: prohibited discharges into the MS4 · checked September 2026
Replacing windows on a San Antonio landmark or in one of its historic districts takes a Certificate of Appropriateness from the city's historic review boards. In 2024 cases, staff recommended repairing original wood windows in kind and did not recommend vinyl or aluminum-clad replacements for windows that could be fixed.
City of San Antonio OHP, Compliance and Technical Advisory Board minutes, February 2024 · City of San Antonio OHP, Compliance and Technical Advisory Board minutes, June 2024 · checked September 2026
What actually shows up on San Antonio glass
The central Texas mountain juniper releases huge volumes of cedar pollen from December through February — locally called cedar fever season. Pollen settles on glass in visible yellow clouds on heavy-release days. Sticks tenaciously and needs a surfactant pass.
Limestone road dust and construction dust from quarry operations west of Austin and around the I-35 corridor produces a fine calcium-rich film on glass. Cumulative; not dramatic, but a contributing factor to the regional hardness staining.
San Antonio, answered
How hard is the water in San Antonio, Texas?＋
San Antonio runs on San Antonio Water System groundwater at a published 257–342 mg/L (CaCO₃) — 15 to 20 grains per gallon in the utility's own words — very hard across the whole span. Fifteen to twenty grains is the top of the scale, and at that concentration water stops being something that spots glass and becomes something that damages it.
How much does window cleaning cost in San Antonio?＋
Residential window cleaning in San Antonio typically runs $10–15 per pane or $300–510 for a standard single-story exterior. Water treatment is a real line item here and almost nowhere else on this site — filtered or deionised rinse is a cost of doing the job rather than an option.
When is the best time of year to clean windows in San Antonio?＋
San Antonio's drier, frost-free months are February, April, July and August and November, by NOAA's 1991–2020 normals for the San Antonio International Airport station, where May brings the most rain. The calendar on this page marks April (after the February 17 bloom) and November (after smoke season and before frost). Frost nights usually run from November 28 to February 26.
Can I rinse windows with San Antonio tap water?＋
Not as the final rinse: San Antonio Water System publishes hardness of 257–342 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 purchased and local supply.
Why do my windows look dirty so quickly in San Antonio?＋
In San Antonio the dominant residue patterns include irrigation overspray etching from very hard supply and cedar and mountain-juniper pollen (december–february). The supply is constant rather than seasonal, so the interval is set by exposure rather than by the calendar — irrigated elevations need attention on a far shorter cycle than sheltered ones on the same house.
Do I need a professional to clean my windows in San Antonio?＋
A homeowner can wash glass in San Antonio; what they cannot easily do is stop it from being ruined. The damage here is cumulative and silent — overspray drying on the same lower panes week after week — and by the time it is visible it is etched rather than dirty.
What sets Downtown and River Walk apart for window cleaning in San Antonio?＋
Pre-1920 commercial core with River Walk frontage and tourist-corridor storefront glass. Appearance standards set by visitor traffic and service windows set around it. Alamo Heights and Olmos Park have their own housing stock and glazing as well.
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