Shirley Water Hardness & Quality Report (2026)

Shirley, New York, in Suffolk County — a major south Long Island Suffolk County community (Shirley is a significant Suffolk County hamlet — a south shore Long Island community adjacent to Mastic and Mastic Beach on the Great South Bay; the Mastic–Shirley area is one of the more economically challenged communities in Suffolk County, located in the Brookhaven Town area; the Shirley–Mastic area is adjacent to the William Floyd Estate (a National Park Service historic site — the William Floyd Estate was the 18th century home of William Floyd, one of the signers of the Declaration of Independence from New York; the estate's main house and outbuildings are preserved on Long Island's south shore)), home of Smith Point County Park (one of the most significant Suffolk County barrier island parks and beach areas), a diverse Suffolk County community with a primarily working-class and lower-middle-class Long Island population, adjacent to Mastic Beach and East Patchogue in the south Suffolk County corridor, and a community shaped by its south shore Long Island character — draws its municipal water supply via the Suffolk County Water Authority. Water hardness in Shirley measures 121 mg/L — classified as moderately hard.

Shirley's moderate hardness reflects the south Suffolk County Long Island aquifer's calcareous-moderate character. The Magothy Aquifer at Shirley draws from Cretaceous calcareous-moderate Magothy Sand with limited softening, producing the moderate 121 mg/L.

At 121 mg/L, Shirley residents encounter moderate scale accumulation. Monthly cleaning is recommended. Suffolk County Water Authority consistently delivers water meeting all New York State DEC and EPA Safe Drinking Water Act requirements.