Randolph Water Hardness & Quality Report (2026)

Randolph, New Jersey, in Morris County receives its municipal water from New Jersey American Water, the state's largest investor-owned water utility. The supply draws from local reservoir impoundments in the Morris County Highlands — principally Splitrock Reservoir and Boonton Reservoir — supplemented by transmission water from the Wanaque Supply System and Raritan Basin reservoirs managed by the New Jersey Water Supply Authority. Water is treated at regional facilities before distribution through the Morris County transmission network to Randolph's townships and residential developments.

The moderate 115 mg/L hardness reflects the geology of the New Jersey Highlands Province — a rugged upland region of Precambrian gneisses, schists, and amphibolites dating back more than one billion years, interspersed with marble and limestone units formed from ancient metamorphosed carbonate sequences. As reservoir water and infiltrating groundwater contact these metamorphic carbonates — particularly the Franklin Marble and associated calc-silicate formations of the northwestern Highlands — moderate calcium and magnesium dissolution occurs, producing the characteristic hardness profile of Morris County supply water.

At 115 mg/L, Randolph's water is moderately hard — comparable to many suburban New Jersey communities. Residents may notice gradual white scale forming inside kettles and along faucet aerators over months, light spotting on glassware from the dishwasher, and modest reductions in soap lather. Descaling appliances every three to six months keeps equipment performing efficiently. The primary water quality concern for Randolph residents is the elevated PFAS level of 9.4 ppt — among the higher readings in northern New Jersey — and residents are advised to use a certified NSF/ANSI 58 reverse osmosis filter for drinking and cooking water as a precautionary measure.