New York City Water Hardness & Quality Report (2026)

The New York City Department of Environmental Protection (DEP) manages the water supply for approximately 8.5 million residents across the five boroughs—Manhattan, Brooklyn, Queens, Bronx, and Staten Island—and additional upstate counties. Water is sourced from 19 reservoirs and 3 controlled lakes: primarily the Catskill/Delaware system (90%, including Ashokan, Schoharie, Rondout, Neversink, Pepacton, and Cannonsville reservoirs) and the Croton system (10%, including New Croton, Cross River, and Titicus). Disinfection occurs via UV light at the Delaware Aqueduct and chloramine addition in distribution; delivery is through 6,000 miles of mains via the Hillview and Kensico tunnels.

The 2,000-square-mile Catskill/Delaware Watershed spans the Catskill Mountains and Delaware Highlands, underlain by Devonian sedimentary rocks—shales, sandstones, and siltstones with minimal limestone—that yield very soft water naturally filtered through forested soils. The Croton Watershed in Westchester and Putnam Counties features Hudson Highlands bedrock of granitic gneiss and schist from the Grenville Province, producing moderately mineralised water. This siliceous, non-carbonate geology limits mineral dissolution, creating a characteristically soft supply prone to low alkalinity.

Soft water creates ample lather with minimal soap, reduces detergent use, and prevents scale buildup in pipes, kettles, and appliances—ideal for laundry and dishwashers with no water softener needed. However, very soft water may corrode older plumbing, accelerating lead and copper leaching in pre-1986 buildings; pipe inspections are advised. pH is typically 7.0–8.0. NYC meets EPA lead and copper rules via corrosion control and pipe replacement, though legacy lead service lines remain a risk—flush taps if concerned. The EWG notes trace trihalomethanes and chromium-6 below legal limits but above health guidelines; no PFAS exceedances reported.