Window Washing in San Jose

San Jose Water publishes a table of hardness by source water type rather than one city figure: groundwater at 183 to 440 mg/L (11 to 26 grains per gallon), imported surface water at 77 to 153 (4 to 9 grains), and a third source at 84 to 198 (5 to 12). That is a nearly six-fold span inside one service area, and the utility states its own threshold — water is hard above 120 ppm or 7 grains.

Most of the valley floor is on groundwater, which is the very hard end. Imported surface water has had far less contact with mineral-rich geology and carries a fraction of the load. A crew that establishes a rinse policy on one side of the service area and carries it to the other will get a different result for reasons that have nothing to do with technique.

At the groundwater end this is among the hardest supplies on this site — 26 grains is comparable to the worst of Arizona and Texas. Deionised or filtered final rinse is not a premium on that side of the city; it is the only way to finish a dark pane cleanly, and irrigation overspray at that concentration etches rather than spots.

Because the split follows the source rather than the neighbourhood boundary, the practical approach here is to establish hardness per route empirically — watch how the glass dries on the first job in an area and set the method from that, rather than from a citywide number that describes nobody.

Decades of tech manufacturing have left a documented groundwater contamination legacy in the Santa Clara Valley. It does not change cleaning method, but it is why the local water conversation is unusually well informed and why customers here ask more specific questions than in most markets.

Eucalyptus and oak pollen overlap in March and April and both stick aggressively. Eucalyptus in particular sheds an oily resinous residue that a pure-water rinse passes straight over — a presoak and surfactant pass is faster than any amount of scraping.

The tech-corridor commercial book concentrates around campus refresh cycles and pulls quarterly contracts at scale. It is modern low- and mid-rise curtain wall rather than high-rise, which keeps access straightforward but puts the work on formal procurement.

Cambrian Park and the mid-century ranch stock carry original aluminium-frame single-pane glazing in quantity. Aluminium frames pit and stain where very hard water sits in the channel, so frame condition is part of the assessment here in a way it is not on newer stock.

Private wells in the Central Valley pump from aquifers that have been concentrating dissolved minerals through decades of irrigation drawdown. 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. Mild on the city side, brutal on the well side, often within the same county.

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.