Selden Water Hardness & Quality Report (2026)

St. James Water District (SJWD), serving Selden and surrounding areas in the Town of Smithtown, Suffolk County, New York, supplies drinking water exclusively from local groundwater aquifers. Water is drawn primarily from the Upper Glacial and Magothy formations through multiple production wells; no surface reservoirs or rivers are involved. Treatment occurs at district facilities encompassing disinfection and basic conditioning. The district serves residential and commercial customers, and the 2024 SJWD Consumer Confidence Report records average hardness at 48 ppm, classified as soft.

The groundwater originates within Long Island's glacial and coastal plain aquifer system, recharged by precipitation infiltrating the sandy soils of Suffolk County. Key geological features include Pleistocene glacial tills and outwash sands together with the underlying Cretaceous Magothy Formation — composed of unconsolidated quartz sands with interbedded clays. The sandy matrix allows dilution by meteoric recharge and limits prolonged contact with high-calcium bedrock, imparting a soft water character unlike systems dominated by carbonate rocks that yield higher mineral content.

Soft water at 48 ppm minimizes scale buildup in household systems — water heaters, dishwashers, and washing machines perform efficiently without mineral deposits clogging pipes or heating elements. Soap and detergents lather well, avoiding scum formation, and fixtures stay cleaner longer. No water softener is typically recommended; routine filter changes and basic descaling suffice. PFAS monitoring adheres to New York State's MCL of 10 ppt for PFOA and PFOS; copper levels (0.043–0.43 ppm) comply with EPA standards. Treatment includes chlorination for disinfection, and no notable violations were reported.