Great Kills Water Hardness & Quality Report (2026)

Great Kills, located in Staten Island, receives its water from the New York City Department of Environmental Protection (DEP), the municipal utility serving over 8 million residents across the five boroughs. The supply is drawn from 19 reservoirs and three controlled lakes in the Catskill/Delaware and Croton systems upstate New York, with primary sources including the Ashokan Reservoir, Schoharie Reservoir, Rondout Reservoir, and Croton Watershed. Water is conveyed via a 100+ mile aqueduct system to treatment facilities, then distributed through local plants on Staten Island for final disinfection before reaching Great Kills homes.

The NYC watershed spans over 2,000 square miles in the Catskill Mountains and Hudson Valley, protected by 2,000 miles of fenced pipeline and forest buffers. Underlying geology consists of ancient metamorphic rocks including Fordham Gneiss and the Hartland Formation (Ordovician age) and sedimentary layers from the Devonian period, with minimal limestone or dolomite. This geology imparts a very soft character to the water, as rainwater percolates through mineral-poor soils and bedrock, dissolving few divalent cations and yielding low overall mineralization.

As soft water, NYC's supply produces minimal scale on fixtures or in pipes, reducing wear on water heaters, dishwashers, and washing machines compared to harder regions. Soap lathers easily and spotting on glassware is rare. No water softener is recommended or needed; however, the low mineral content can be mildly aggressive on metal plumbing, so occasional corrosion checks are advisable. NYC DEP water meets or exceeds EPA standards with pH typically 6.8–7.2 for stability. The system complies with the Lead and Copper Rule via corrosion control programs; PFAS levels are below advisory limits with granular activated carbon used if detected. UV disinfection has been employed since 2013 to address cryptosporidium risk alongside primary chlorination.