NYC Has Soft Water — Here's What That Changes for Washing Your Car
Skip the distilled water, worry less about spots, and expect rinseless products to work at full strength straight from the tap.
Most car-detailing advice about water spots and distilled water is written by people in hard-water places. If you're in New York City, a lot of it doesn't apply to you.
The numbers
NYC's supply comes mostly from the Catskill and Delaware reservoirs, which sit on hard bedrock that dissolves very little calcium or magnesium into the water. Hardness typically runs around 1 to 2 grains per gallon (roughly 20 to 35 mg/L). Anything under about 3.5 gpg is classified as soft; "hard" starts around 7. The small Croton portion of the supply is a bit harder, so parts of the Bronx and upper Manhattan can see slightly higher readings, but still nowhere near hard-water territory. Compare that with 10 to 20 gpg in Phoenix or much of Southern California.
What it means in practice
Rinseless and waterless products foam, lubricate, and encapsulate better in soft water, so you'll get the most out of them straight from the tap. There's no reason to buy distilled water for the bucket or the sprayer.
Water spotting is a much smaller concern. Spots are mostly the dissolved minerals left behind when a drop evaporates; NYC water has very little to leave. You'll still want to dry the car rather than let it bake in the sun — there's always some residue, plus whatever was already on the paint — but the "dry every drop instantly or regret it" urgency that hard-water people live with doesn't apply here.
Nozzle and filter clogging in pump sprayers comes from dried product residue, not mineral scale, at these hardness levels. Rinse the sprayer after use and you're fine.
The one caveat
If your water comes from a building's own tank or a source outside the city system, check it; and if you move to Long Island, much of New Jersey, or the Southwest, the calculus changes and distilled water starts making sense for the final rinse.
Have a hose? Same story: tap water is fine for the rinse. If your bay or hose offers a spot-free rinse it's cheap insurance, but it's not the necessity it is elsewhere.