Hillside Water Hardness & Quality Report (2026)

Hillside, New York, in Queens County on Long Island's western end, receives its municipal water from the New York City Department of Environmental Protection (DEP), which operates one of the largest unfiltered water supply systems in the United States. NYC DEP draws from three major watershed systems — the Catskill System (Esopus Creek watershed, Catskill Mountains), the Delaware System (Delaware River headwaters), and the Croton System (Westchester and Putnam counties) — delivering water to all five boroughs through an extensive underground aqueduct and tunnel network.

The hard 159 mg/L hardness in Hillside is noticeably higher than typical Catskill or Delaware watershed water (~50–80 mg/L), indicating significant contribution from the Croton watershed system. The Croton watershed in Westchester and Putnam counties crosses the Hudson Highlands where Paleozoic carbonate formations — including Inwood Marble and Fordham Gneiss carbonate lenses — contribute dissolved calcium and magnesium to reservoir water. The Croton system consistently delivers harder water (120–160 mg/L) than the Catskill-Delaware mountain supply, and Queens distribution zone blending with Croton water elevates the finished hardness in eastern Queens neighborhoods including Hillside.

At 159 mg/L, Hillside residents deal with hard water that produces noticeable mineral effects throughout the home. Kettles and coffee machines accumulate white scale over weeks, dishwashers leave mineral deposits on glassware, and bathroom fixtures develop calcium rings over time. Descaling appliances every two months is recommended. The PFAS level of 7.6 ppt — elevated for the NYC metro area — likely reflects industrial and landfill activity in the Queens-Nassau County corridor. A certified reverse osmosis or activated carbon block filter is a practical investment for daily drinking water protection.