Yonkers Water Hardness & Quality Report (2026)

Yonkers Joint Water Works supplies drinking water to approximately 211,569 residents in Yonkers, New York, within Westchester County. Water is sourced primarily from New York City's Delaware Aqueduct and connections to Westchester County Water District #1's K-B South Pipeline, drawing from 19 reservoirs and three controlled lakes across a nearly 2,000-square-mile watershed. The supply enters 385 miles of distribution piping after upstream treatment at Kensico Reservoir by the NYC Department of Environmental Protection (DEP), serving 29,186 metered connections without local treatment plants named in reports.

The Croton-Delaware watershed spans the Catskill Mountains and Hudson Highlands, underlain by ancient Precambrian gneisses, schists, and granites with minor Paleozoic sedimentary overlays. This non-carbonate geology yields very soft water due to the low solubility of calcium and magnesium from these rock types. Protected forested lands limit sediment and ion leaching, maintaining the supply's characteristically soft profile as it flows through Kensico Reservoir before distribution.

As soft water, Yonkers' supply causes minimal scale buildup in pipes, heaters, and appliances, reducing maintenance needs for dishwashers, washing machines, and water heaters. Soap and detergents lather easily. No softener is recommended; instead, monitor for corrosion risks in hot water systems — use anode rods in tanks and periodic flushing to prevent pinhole leaks from low mineral buffering. Water quality testing shows compliance with federal limits, with 0 MCL violations; two contaminants exceed EPA health-based MCLGs but remain within legal MCLs, so certified filters are advised for vulnerable groups. The 2016 CCR notes total hardness ≈20 mg/L as CaCO3. Treatment includes upstream chlorination at Kensico and fluoride addition.