Allentown Water Hardness & Quality Report (2026)

Allentown, Pennsylvania, the third-largest city in Pennsylvania and the Lehigh Valley's largest city, draws its municipal water supply from the Allentown Bureau of Water, sourcing from the Little Lehigh Creek via the Little Lehigh Creek Wellfield — a series of collector wells in the Little Lehigh Creek streambed — and the Crystal Spring groundwater source in Lehigh County. The Little Lehigh Creek drains the Lehigh Valley between South Mountain and the Kittatinny Ridge in Lehigh County. Water is treated at the Keck Memorial Filtration Plant before distribution throughout Allentown. Water hardness measures 89 mg/L — classified as moderately soft.

Allentown's moderately soft supply is somewhat unexpected given the Great Valley Carbonate Belt underlying much of Lehigh County. The Little Lehigh Creek wellfield draws primarily from alluvial aquifer gravels in the Little Lehigh Creek floodplain — a Quaternary alluvial aquifer recharged by streambank infiltration. While the Lehigh Valley bedrock includes the Ordovician Jacksonburg Limestone, Cambrian–Ordovician Beekmantown Dolomite Group, and other Valley and Ridge carbonate formations, the shallow alluvial wellfield draws from recent stream-recharged gravel with relatively short groundwater residence times, limiting carbonate equilibration. The Crystal Spring source similarly draws from less mineralized fracture flow zones.

With hardness at 89 mg/L, Allentown residents experience light to moderate scale accumulation. Faucet aerators and showerheads develop deposits slowly — bi-monthly cleaning with citric acid solution is sufficient. Dishwashers produce clean glassware with light rinse-aid use. Hot water systems accumulate modest scale. Allentown Bureau of Water consistently delivers water meeting all Pennsylvania DEP and EPA Safe Drinking Water Act requirements.