Massapequa Water Hardness & Quality Report (2026)

Massapequa, New York, in Nassau County — a large south shore Long Island community in the Town of Oyster Bay, bordering the Massapequa Preserve (a state-protected freshwater estuary), known as an archetypal postwar Long Island suburb and home of the original Tommy Hilfiger store — receives its municipal water from the Nassau County Water Authority (NCWA), which draws from the Long Island Glacial Aquifer system — primarily the Upper Glacial Aquifer and the deeper Magothy Aquifer — through production wells distributed across Nassau County. Long Island's entire water supply depends on this glacial aquifer system.

The moderately hard 168 mg/L hardness and elevated TDS of 433.9 mg/L are characteristic of the Long Island Glacial Aquifer in Nassau County. The Long Island Glacial Aquifer taps Pleistocene glacial outwash sand and gravel deposits — material deposited by the Wisconsin ice sheet as it retreated — overlying the Cretaceous Raritan Formation (non-marine sands and clays) and the Magothy Formation (marine sands). These Cretaceous and Pleistocene formations are primarily siliciclastic (sand and gravel) rather than carbonate, but moderate dissolved mineral content accumulates from the Long Island subsurface as recharge percolates through the island's soils and subsoils. The Nassau County zone produces harder, higher-TDS water than the typically softer Suffolk County wells farther east, reflecting Nassau's older, deeper, and more mineral-contacted aquifer production.

At 168 mg/L, Massapequa's water is moderately hard. Scale builds in kettles and appliances over months, dishwashers benefit from rinse aid, and faucet aerators need periodic cleaning. Quarterly descaling of heating appliances is appropriate. The PFAS level of 8.0 ppt warrants a certified drinking water filter — Nassau County's Long Island Glacial Aquifer has been significantly affected by PFAS from legacy dry cleaners, military installations (Grumman aerospace's Bethpage complex and Mitchel Field in Garden City), and the dense suburban Nassau County industrial and commercial PFAS sources that have historically contaminated numerous Nassau County wells.