Lima Water Hardness & Quality Report (2026)

Lima, Ohio, the Allen County seat — a major northwest Ohio manufacturing city, birthplace of the American M4 Sherman tank (the Lima Locomotive Works in Lima, Ohio produced the M4 Sherman tank and other armored vehicles that were pivotal in World War II — the M4 Sherman was the primary American tank in WWII), a historic petroleum industry city (Lima was a major center of Ohio petroleum production in the late 19th century — the Lima oil field was one of the largest in the world in the 1880s), and a diverse northwest Ohio community — draws its municipal water supply from the Ottawa River watershed and Silurian Niagaran Dolomite wells via the City of Lima Water Division. Water hardness in Lima measures 149.5 mg/L — classified as moderately hard.

Lima's moderate hardness reflects the northwest Ohio Ottawa River watershed's calcareous geology. The Ottawa River at Lima–Allen County and the Silurian aquifer draws from: the Silurian Niagaran Dolomite (highly calcareous dolomite of the Indiana–Ohio border zone, primarily the Lockport Dolomite); the Wisconsin Age Lake Erie Lobe calcareous till (calcareous glacial deposits from the western Lake Erie Basin ice lobe); and the Devonian calcareous limestone of the Ottawa River watershed. City of Lima's treatment produces the moderate 149.5 mg/L.

At 149.5 mg/L, Lima residents encounter moderate-to-hard scale accumulation. Monthly cleaning with citric acid solution is recommended. City of Lima Water Division consistently delivers water meeting all Ohio EPA and federal EPA Safe Drinking Water Act requirements.