Hillsborough Water Hardness & Quality Report (2026)

Hillsborough, New Jersey is served by New Jersey American Water (NJAW), specifically the Raritan System 2 division, which supplies approximately 615,430 people across Hunterdon, Mercer, Somerset, and surrounding counties. The utility operates multiple treatment plants and draws from both surface water sources — the Raritan River and associated reservoirs — and groundwater aquifers to meet regional demand throughout central New Jersey, with all operations reported to the EPA and compliant with federal and state drinking water standards.

The Raritan River watershed drains the New Jersey Piedmont and contributes surface water that interacts with Devonian and Ordovician carbonate-rich bedrock formations. Groundwater sources tap into the New Jersey Piedmont aquifer system, where water percolates through limestone and dolomite layers dissolving calcium and magnesium minerals. This geological setting — characteristic of central New Jersey — naturally produces a hard water supply through the blending of mineral-rich surface and groundwater sources drawn from these ancient bedrock formations.

At 156 mg/L, hard water in Hillsborough causes noticeable scale buildup in kettles, coffee makers, water heaters, dishwashers, and washing machines, with reduced soap lathering and potential dry skin. Appliances experience shortened lifespans from mineral deposits, and a water softener is recommended to protect plumbing and household appliances from accelerated wear. The utility reports a pH range of 6.5–8.5; third-party data indicates 7 contaminants above EPA MCLGs (Maximum Contaminant Level Goals), though no MCL violations have been recorded, and residents with private wells are responsible for independent testing through certified New Jersey laboratories.