The most varied water profile of any state — a patchwork of six major districts, each with its own source, treatment, and hardness profile, plus a meaningful population of Central Valley wells.
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The Park Fire burned three hundred and seventy thousand acres in Butte and Tehama counties in the summer of 2024. It was, at the time, the fourth-largest wildfire in modern California history. The smoke from the fire reached the Bay Area on a Sunday evening in late July, settled into the inland valleys overnight, and produced an air-quality index reading of one hundred and eighty-seven in Oakland by Monday morning. The smoke remained for six days. When it cleared, every horizontal glass surface in the inner East Bay was wearing a fine carbonaceous film, and every cleaner with a residential book in the area had a Tuesday-morning voicemail queue that ran into the dozens.
I have a customer in Rockridge, four blocks from the College Avenue commercial strip, whose house I have cleaned quarterly since 2018. She called me at six in the morning on the Tuesday after the air cleared and asked, with the politeness that defines our long working relationship, whether I might be able to come earlier than my scheduled visit, which was three weeks away. I told her I would come Wednesday. She told me she would put the coffee on. I drove out at seven the next morning, parked behind a 2014 Subaru with a Sierra Club bumper sticker, and saw, before I had even reached the front porch, that the entire south face of the house — three large picture windows, two sets of French doors onto the patio, and a clerestory band above the kitchen — was wearing a uniform pale-brown film that had not been there six weeks before.
This is the story of California window cleaning over the last decade, and it is the story that I think the trade press has not yet fully understood. The water is the water. The water has been the water for thirty years. The new working problem in this state is wildfire smoke, and the new cleaning protocol is one that the working cleaners here have been developing in the field for the last ten years because the published trade literature has not caught up.
I am writing this piece because I came to the trade in 2016 from five years in environmental consulting, where I worked on California water-quality regulation, and because I have spent the ten years since trying to apply the systems thinking from my previous career to the question of what cleaning a window in California actually requires. The state is the most varied I have worked in. The water alone is six districts and a Central Valley well-water question, and that is before you get to the smoke.
California is not a single water market. It is, for the working cleaner, at least six water markets, each with its own source, treatment, and behavior on glass. Cleaners who learn the trade in one district and move to another can be surprised by how different the next district's water is, and customers who move within the state often complain to me, in their first months at a new house, that their windows do not stay clean the way they used to. They are not wrong. The water has changed.
SFPUC (Hetch Hetchy) serves the city of San Francisco and most of the Peninsula. The supply is gravity-fed by aqueduct from the Hetch Hetchy reservoir in the Sierra Nevada and arrives at the tap at 70-90 mg/L of total hardness. This is soft-to-moderate water by national standards and is, of the major California districts, the easiest water to clean with. The SF customers I have do not require a distilled rinse on routine work. The cleaning challenges in San Francisco are atmospheric — fog, salt aerosol from the Pacific, and a meaningful population of pre-war wood-sash glass in the older neighborhoods — but the water itself is not a deposit problem.
EBMUD (Mokelumne) serves Oakland, Berkeley, and most of the East Bay flatlands and inner hills. The supply comes from the Mokelumne River in the Sierra and is similar in character to Hetch Hetchy — soft to moderate, 70-100 mg/L on most of the service area. The East Bay drinks Sierra snowmelt the way San Francisco does, and the cleaning implication is the same: water is not the dominant working problem. The atmospheric particulate, the salt aerosol off the Bay, the marine-layer condensation, and the wildfire smoke are the considerations that matter.
Santa Clara Valley Water serves San Jose, Cupertino, Mountain View, and the South Bay. The supply blends State Water Project deliveries (the same Sacramento Delta water that supplies most of Southern California) with local reservoir water and groundwater. Hardness runs 200-280 mg/L, which is firmly hard. The cleaning implication is that the South Bay and the East Bay are on different water profiles despite being a thirty-minute drive apart. A cleaner who learns the trade in Oakland and picks up a customer in Mountain View is going to be surprised. I was surprised, on the first South Bay account I picked up in 2018, and I have not forgotten the lesson.
Metropolitan Water District (MWD) is the wholesale supplier to most of the greater Los Angeles metro and a meaningful portion of San Diego County. The MWD blend is Colorado River water (via the Colorado River Aqueduct) and State Water Project water (via the California Aqueduct) in proportions that vary year to year depending on drought conditions and contract obligations. The retail districts that MWD serves run hard, in the 250-350 range, and the blend shifts seasonally. In drought years, the Colorado fraction increases and the water runs harder. In wet years, the SWP fraction increases and the water runs slightly softer.
LADWP serves the city of Los Angeles proper on a separate system. LADWP blends MWD imports with Owens Valley aqueduct water — the famous aqueduct that William Mulholland built in 1913 and that has been the political fault line of Southern California water ever since — and produces a slightly softer blend than the greater MWD service area. LADWP runs 180-260 on the year. The Owens Valley fraction is what keeps the city tap softer than the suburban one.
San Diego County Water Authority serves greater San Diego with a blend that is heavily MWD-dependent but has, in the last fifteen years, added a meaningful and growing fraction from the Carlsbad desalination plant. The Carlsbad water arrives at the blend point at a different mineral profile from the imported water, and the resulting tap water in the parts of San Diego that receive a high desalination fraction runs slightly differently on glass — slightly less calcium scaling, slightly more residual chloride film if not rinsed properly. The desalination fraction is going to grow. I have visited Carlsbad. I have visited Huntington Beach. I have a long argument with myself that I keep not finishing about what the desalination shift is going to do to the SoCal cleaning trade over the next twenty years, and I will spare you the long version here. The short version is: pay attention.
The summary, for the cleaner working a regional California route: ask which water district the customer is on before you quote. The same protocol that works in Pacific Heights does not work in Pasadena, and the same protocol that works in Pasadena does not work in San Jose. The water is not one thing in this state.
The other water consideration in California, separate from the municipal districts, is the well-water population of the Central Valley.
The Central Valley — the Sacramento-San Joaquin watershed that runs from Redding in the north to Bakersfield in the south — is the agricultural engine of the state and the most heavily groundwater-dependent region in the country. The aquifers beneath the Central Valley have been pumped for more than a hundred years to support irrigated agriculture, and the cumulative drawdown has, in many sub-basins, concentrated dissolved minerals in the remaining groundwater to a degree that produces some of the hardest residential water in the state. Well-water households on the Valley floor — not the cities, which are on blended municipal supplies, but the agricultural-adjacent residences outside the city limits — can pump water that runs anywhere from three hundred to over four hundred and fifty milligrams per liter of total hardness, with nitrate, arsenic, and in some sub-basins boron at levels that produce public-health concerns separately from the cleaning concerns.
I do not work the Central Valley on a regular basis. The cleaning operators based in Fresno, Bakersfield, Modesto, and Stockton are the people who handle the well-water households directly, and a few of them have hired me as a consultant on particular protocol questions over the years. The pattern that has emerged from those consulting jobs is, I think, worth documenting:
The right protocol for a Central Valley well-water household is, as Jerry Davenport has written about hill-country wells in Texas, a whole-house water softener plus a separate distilled-rinse protocol on the windows. Without the softener, the distilled rinse alone is fighting a losing battle against the irrigation system, which is depositing fresh deposits on the glass on every cycle. With the softener, the distilled rinse is a maintenance protocol that works. About half of the well-water households I have consulted on have installed a softener. The other half have not, and the cleaning operators who service those houses come back every six to eight weeks instead of every quarter, and the customer eventually decides that the windows just are not cleanable, and they are not wrong.
A second consideration: the iron content in some Central Valley wells. Iron in the well water produces an orange tint on the calcium deposit that the standard citric-acid protocol does not fully clear. The right move for iron-stained deposits is the oxalic-acid pre-treatment that Jerry has documented in his Texas piece — the protocol is identical and the chemistry is identical. The Central Valley iron-rich wells are concentrated in particular geological sub-basins that the local cleaning operators can usually identify by address.
There is a coastal-to-inland gradient in California water that the cleaner working a route across that gradient should understand. The Bay Area coast runs soft. The Central Valley inland runs hard. The Sierra foothills, somewhere between, run on a mix of municipal supplies and private wells with their own profiles. A cleaner whose route crosses the Coast Range from Oakland into Livermore or from San Francisco onto the Peninsula and then over to the South Bay is crossing two or three water profiles in a single workday, and the protocol changes with each crossing.
The cleaning consideration that has reshaped the California trade in the last ten years is wildfire smoke.
The California fire season, historically a June-through-October phenomenon concentrated in the foothill and mountain zones, has expanded in duration, intensity, and geographic reach to a degree that the working trade has had to adapt to. The 2017 Tubbs Fire, the 2018 Camp Fire, the 2020 August Complex, the 2024 Park Fire, and dozens of smaller events have each, in their event window, produced statewide or near-statewide smoke deposition that has reached every major metro and, in some events, every glass surface in the state.
The deposition pattern is consistent across events. A heavy smoke event deposits a fine carbonaceous film on horizontal glass within twelve hours, on the upper third of vertical glass within twenty-four to thirty-six hours, and on the rest of vertical glass within seventy-two to ninety-six hours. The film is composed of fine particulate matter — primarily black carbon and organic aerosols — with embedded mineral content from any structures that burned in the fire. The film is more cohesive than ordinary atmospheric particulate; it bonds to glass with a faint resinous quality that ordinary cleaning solution does not always lift on the first pass.
The protocol that has emerged from the field — not from the published trade literature, which has not, in my reading, caught up to this question — is approximately:
First, a generous surfactant pre-rinse. The smoke film responds better to a high-surfactant solution than to the standard House Standard at three drops of Dawn. I use five to six drops per gallon during the immediate post-smoke window. Mara Whitfield does not love this. The argument is documented in our Slack.
Second, a longer dwell time. Where the standard residential pre-wash is in the thirty-second range before the squeegee comes through, the smoke-event protocol benefits from sixty to ninety seconds of dwell. The surfactant needs time to break the resinous bond, and the squeegee that comes through too early leaves a streak that no detailing pass will fully fix.
Third, two passes on the worst-affected exposures. The single-pass standard residential protocol does not always clear a heavy smoke film on the first application. The right move on the worst exposures is a standard wash, a five-minute pause, and a second standard wash. Two passes clears what one pass cannot.
Fourth, and most importantly, communication with the customer. The post-smoke cleaning cycle does not get a window back to the baseline that the customer remembers from before the smoke. There is, on most glass, a residual haze that takes two or three full quarterly cycles to fully clear, because the smoke has worked into the micro-pitting of the glass surface and is being released gradually by subsequent water exposure. Telling the customer this in advance — gently, without alarm, with a plan — is the difference between a customer who understands the work and a customer who decides their cleaner is not delivering what they remember from 2019.
Mara has written about why your windows look worse after you clean them in a different context. The post-smoke equivalent of that piece has not yet been written for the site. I owe it. I am working on it.
The seasonal cleaning calendar in California is structured around the rain cycle, the wildfire cycle, the pollen wave, and the regional climate patterns that affect each metro differently.
December through March is the wet season in northern California and the Bay Area, and the dry season in southern California. The Bay Area sees its annual rainfall — typically twenty to thirty inches — almost entirely in this window. Residential exterior work in the Bay Area is reduced during this period; many Bay Area operators run a winter LA route, the way snowbird operators in the Midwest run a Florida route, and I am one of them. The LA winter season is, in my experience, the best working window of the year in southern California. The air is clear, the rain is intermittent, the temperatures are workable, and the southern-California customer base is at peak demand for pre-holiday and post-rain cleanings.
Late March through May is the spring peak in the Bay Area and northern California. The post-rain cleanup drives volume; the pollen wave layers in. Eucalyptus and oak pollen produce a yellow film on east-facing exposures from February through May. Cottonwood appears in pockets in May. The Sierra-foothill markets — Auburn, Placerville, Sonora — see their own pollen pattern slightly later than the coast.
June through August is the Bay Area summer fog season. The marine layer produces sustained morning condensation on east-facing glass that redeposits atmospheric particulate as a thin film. The right move on Bay Area summer mornings is to start east-facing work after the fog has lifted, typically around ten in the morning. The Central Valley and the Inland Empire run their hottest months in this window. South-facing glass in Fresno in July can hit a hundred and twenty-five degrees at noon and requires the morning-only shift that Jerry Davenport documents for Texas in August — the heat-load problem is the same physics in either state.
August through October is the wildfire season. The cleaning calendar in this window is event-driven rather than calendar-driven; in low-fire years the work proceeds at normal cadence, and in high-fire years the schedule is restructured around the smoke events. The 2020 season, the 2024 season, and to a lesser extent the 2018 season produced statewide smoke events that reorganized everyone's books. Planning for this is operationally difficult and I have, in the last three years, started keeping a small reserve of unbooked Tuesdays specifically for post-smoke unscheduled work.
October through December is the second peak. Pre-holiday cleaning drives October and November. The atmospheric rivers that produce the heaviest winter rain in northern California typically begin in late October. The LA market runs at steady volume through this season; the Bay Area book starts to thin in mid-December.
Greater Los Angeles is the largest single metropolitan window-cleaning market in the country, by volume of glass, and the most complex by water-district patchwork. Within the metro, LADWP serves the city proper, MWD member agencies serve most of the suburbs, and the smaller specialty districts (Beverly Hills Public Works, Pasadena Water and Power) serve their own micro-areas with their own profiles. A regional route that crosses two or three districts in a day will see two or three water profiles on the glass.
San Diego County is a smaller, simpler market than LA — most of the metro is on the SDCWA blend — but with the growing Carlsbad desalination fraction and the coastal salt aerosol consideration as the dominant working concerns. The clientele runs upper-income on the coastal exposures and tracks the high-end Long Island or coastal Florida market for service expectations.
The Bay Area is six counties and at least four water districts and is the most operationally complex region in the state for a regional cleaner. SF on Hetch Hetchy, the East Bay on EBMUD, the South Bay on Santa Clara Valley, Marin on Marin Municipal, and several smaller districts in Solano and Sonoma counties. The cleaning protocols vary by district. The customer expectations vary by neighborhood. The drive times vary by traffic in a way that affects route economics significantly.
The Central Valley metros — Sacramento, Stockton, Modesto, Fresno, Bakersfield — are smaller markets with the standard Valley considerations: mostly hard municipal water, hot dry summers, well-water households on the periphery, and a meaningful population of agricultural-adjacent commercial accounts. The trade in these cities is, in my experience, less competitive than in the coastal metros and the opportunity for a focused operator is real.
The North Coast and the Sierra foothills are small markets with high seasonal variability. The wildfire reconstruction work has produced, in some of these communities, a temporary boom in new-construction cleaning that has substantially changed the local economics. The Paradise area in particular has seen a meaningful build-back of new housing over the last five years, almost all of which has been cleaned, at some point in the construction process, by an operator I know.
The California trade in 2026 is shaped by three things: the maturation of the wildfire-cleaning protocol I described above, the slow shift of the LA basin water profile as desalination scales up, and the continuing aging-out of the first-generation immigrant operators who built most of the long-running family-route businesses in the state.
The opportunity for a new operator in California is, in my view, significant but specific. The market is not undersupplied in the absolute sense; the major metros have plenty of cleaners. The market is undersupplied in the specific sense — there are not enough operators who understand the water-district patchwork, the post-smoke protocol, and the substrate considerations of the pre-war stock in the older Bay Area, LA, and Pasadena neighborhoods. The operator who can demonstrate, on the first job, that they know which water district the customer is on and what that district's water does on glass, will, in my experience, hold the customer.
A note on certification and licensing: California requires a contractor's license for work above a certain dollar threshold (currently five hundred dollars per job, including labor and materials). The residential window-cleaning trade falls below this threshold on most individual jobs but can cross it on larger commercial work, and the operator who plans to do commercial work should hold the license or work under one. The licensing exam is administered by the Contractors State License Board and is, by the standards of contractor licensing in other states, not unusually onerous. The trade press undersells the importance of this license. Get it before you need it.
A second note: California's air-quality regulations, particularly in the South Coast Air Quality Management District (the LA basin), affect which cleaning chemicals can be used in commercial volumes. The volatile organic compound limits on solvents are tighter in California than in most other states, and the operator who is moving here from a less-regulated state should review their solvent inventory. Jan Davenport's solvent ladder piece covers the chemistry; the California-specific adjustment is to favor the lower-VOC alternatives within each tier of the ladder.
If you are a homeowner in California trying to figure out the cleaning protocol for your house, the short version is this: identify your water district, identify your wildfire exposure, identify the age and substrate type of your housing stock, and find a cleaner who can describe all three to you on the first phone call. The Bay Area homeowner whose cleaner does not know the difference between EBMUD and Santa Clara Valley is missing context that affects their work. The LA homeowner whose cleaner has not adapted to the post-smoke protocol is paying for service that does not match the conditions.
If you are a cleaner moving to California or starting in the trade here, the longer version is: spend the first three months learning the water districts. Read the consumer confidence reports for every district whose customers you intend to serve. They are public, they are mandatory, and they tell you exactly what the water is doing at the tap. Read the canonical pieces on this site — the four-stage wash, the glass types overview, the streaks diagnostic piece — and then go work for somebody for a season before you take on customers of your own. The state is too varied to learn from books, and the working knowledge of the post-smoke protocol, the pre-war Pasadena and Hancock Park substrate considerations, and the Central Valley well-water question is held by the practicing operators and not in any published manual.
I have been doing this for ten years. I am still learning. The state is, in my experience, the most interesting place in the country to do this work, in part because the trade in California is still in active development — the protocols are still being written, the substrate considerations are still being documented, and the operators who are doing serious work are still figuring out, in real time, how the wildfire era is going to change the practice over the next twenty years. The desalination shift is coming. The water profile of the LA basin is going to change. The fire calendar is, by every available indication, going to expand further. The cleaner who is paying attention is going to be ahead of the cleaner who is not.
I think it is the best job in the country and I do not intend to do it anywhere else.
LADWP blends MWD imports (Colorado River, State Water Project) with Owens Valley aqueduct water. Hardness varies seasonally with the blend ratio; expect 180-260 mg/L on the year. The Owens Valley fraction is what keeps LADWP softer than greater MWD service.
San Diego draws heavily from imported MWD water plus a growing fraction from the Carlsbad desalination plant. Hardness runs hard at 260-320 mg/L. Coastal salt aerosol is the secondary cleaning consideration.
Santa Clara Valley blends State Water Project imports with local reservoir water and groundwater. Hardness runs moderate-to-hard at around 240 mg/L. South Bay is harder than the EBMUD-served East Bay.
SF drinks Hetch Hetchy reservoir water from the Sierra Nevada, gravity-fed by aqueduct. Hardness runs 70-90 mg/L — among the softest municipal water in any major California city. The fog and the salt aerosol are bigger working considerations here than the water.
Fresno blends groundwater with surface water from the Kings and San Joaquin rivers. Hardness runs around 280 mg/L on municipal supply. The cleaning-relevant consideration in this region is the well-water households outside the city limits, which can run 350-450+.
EBMUD draws from the Mokelumne River in the Sierra. Hardness runs soft-to-moderate at 70-100 mg/L. Berkeley, the East Bay flatlands, and the inner-ring hills all share the same supply. Marine layer fog and salt aerosol are the dominant atmospheric considerations.
Each city page carries its own water profile, neighborhood breakdown, cost range, and city-specific operating notes.
| CONTAMINANT | SEASON | SEVERITY |
|---|---|---|
| Wildfire smoke ash | Aug-Oct (event-driven) | severe |
| The defining cleaning consideration of California in the last decade. Wildfire smoke deposits a fine carbonaceous film with embedded fine particulate that bonds to glass and requires a surfactant pass to remove. The film can deposit overnight in event-heavy years and recurs faster than normal cleaning cadences anticipate. | ||
| Coastal salt aerosol | year-round (peaks Nov-Mar) | high |
| The Pacific coast from San Diego to Eureka sees salt aerosol year-round, heaviest during winter storm season. The Marin headlands, the San Francisco Sunset, the Big Sur coast, and the Malibu beach properties are the heaviest-deposition areas. Salt corrodes aluminum sash hardware over time. | ||
| Marine layer fog and condensation | May-Aug (Bay Area, coastal) | moderate |
| The Bay Area summer fog produces sustained morning condensation on east-facing exposures that redeposits atmospheric particulate as a thin film. Standard cleaning protocols work; the consideration is the cleaning cadence — coastal SF and the Marin shoreline want more frequent service than inland equivalents. | ||
| Central Valley well water | year-round | severe |
| Private wells in the Central Valley pump from aquifers that have been concentrating dissolved minerals through decades of irrigation drawdown. Hardness can exceed 450 mg/L. Nitrate and arsenic are public-health concerns in specific sub-basins; the same water that produces the public-health flag also produces the heaviest hard-water deposits. Soft on the city side, brutal on the well side, often within the same county. | ||
| Eucalyptus and oak pollen | Feb-May | moderate |
| California live oak and the introduced eucalyptus release pollen on overlapping schedules from February through May. Eucalyptus pollen is the harder to clear — it carries a faint resinous component that does not respond fully to plain water and requires a surfactant pass. | ||
| Sprinkler overspray (greater LA, San Diego) | year-round (peaks Apr-Oct) | high |
| Greater LA and San Diego are heavy irrigation markets and the municipal hardness exceeds 250 mg/L. Sprinkler overspray onto patio doors and ground-floor glass produces the same mineral-cement deposit pattern documented in San Antonio and Phoenix. Pre-WWII glass in Hancock Park and similar neighborhoods is at particular risk for cumulative etching. | ||
March through May is the coastal peak. The post-winter-rain pass drives the call volume in the Bay Area and northern California. LA runs steady through this season — the dry winters do not produce the same seasonal demand spike.
June through August is steady residential. The marine-layer cities run cool enough that flash-evaporation is not a working problem; the inland and Central Valley markets run morning-only shifts during the hottest weeks.
September through November is the wildfire-driven season. Post-smoke-event cleanings drive significant unscheduled volume in event years. Pre-holiday work begins in October.
December through February is the Bay Area rainy season and the LA dry season. Bay Area residential exterior work is reduced; LA residential exterior work is at peak. Many Bay Area operators run a winter LA route the way snowbird operators run a Florida route.
Land-adjacent states each get their own water-and-window profile. If you're working a regional route or moving across the border, these are the natural next reads.
Municipal water in California typically runs 60–450 mg/L (CaCO₃), which is in the moderate range typical for most US markets. Hardness varies by city and source; check the city-by-city breakdown below or use our ZIP-code hard-water tool for a closer reading.
In California, the working operator's calendar typically favors fall — september through november is the wildfire-driven season. post-smoke-event cleanings drive significant unscheduled volume in event years. pre-holiday work begins in october. For a full seasonal breakdown, see the cleaning calendar section on this page.
Residential window cleaning in California typically runs $8–18 per pane or $200–500 for a standard single-family house exterior, depending on metro pricing, story height, screen condition, and frame type. Use our cost estimator for a calibrated quote for your home.
The dominant residue problem in California is wildfire smoke ash (Aug-Oct (event-driven)). The defining cleaning consideration of California in the last decade. Wildfire smoke deposits a fine carbonaceous film with embedded fine particulate that bonds to glass and requires a surfactant pass to remove. The film can deposit overnight in event-heavy years and recurs faster than no
Single-story homes with accessible glazing can be cleaned by homeowners using basic squeegee technique and the right solution. Multi-story houses, post-2010 coated glass, hard-water markets, and screens-plus-tracks work usually pay for themselves with a professional. See our hiring checklist below.
Wildfire smoke deposition is the single biggest cleaning-relevant change to California in the last decade. Smoke from the August-October fire season can deposit a fine carbonaceous film across the entire state in a way that requires its own protocol. Atmospheric river events in winter produce sudden heavy rain on previously dust-coated glass. Drought cycles affect water-quality
Los Angeles is the largest market in California and has the deepest concentration of professional window-cleaning services. Use our "Find a Cleaner" page to be matched with vetted local pros, or read the Los Angeles section of this page for the city-specific water and cleaning context.
Easton Giordano is part of the Giordano Inc. editorial team and covers the Pacific Northwest and West Coast editorial beat for Window Washing Guide. Editorial content is researched and reviewed in collaboration with the Giordano Inc. editorial team and informed by interviews with practicing window-washing operators in the region, plus published trade and materials-science references.
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