Plymouth Water Hardness & Quality Report (2026)

Plymouth, Minnesota — the largest suburb of Minneapolis in western Hennepin County (consistently ranked among America's best places to live) — draws its municipal water supply through the City of Plymouth Utilities Water Division, sourcing from a blend of Minneapolis Water Works treated Mississippi River water distributed through the western Hennepin County regional grid and local City of Plymouth groundwater wells accessing the Jordan Sandstone and Prairie du Chien Group aquifer system. Water hardness in Plymouth measures 128 mg/L — classified as moderately hard.

Plymouth's moderate hardness reflects the western Hennepin County water blend. The Minneapolis Water Works Mississippi River supply is inherently moderately hard (the Mississippi River at Minneapolis collects drainage from the calcareous Cambrian Jordan Sandstone and Ordovician Prairie du Chien Dolomite outcrops in southeastern Minnesota). Local Plymouth groundwater from the Jordan Sandstone aquifer (Upper Cambrian) intercommunicates with the Prairie du Chien Dolomite (Lower Ordovician — a highly reactive calcareous dolomite), contributing dissolved calcium and magnesium. The Plymouth area's blend of these sources produces the 128 mg/L moderately hard reading consistent with the western Minneapolis suburban ring.

At 128 mg/L, Plymouth residents encounter moderate scale accumulation. Faucet aerators and showerheads develop deposits after several months — monthly cleaning with citric acid solution is practical maintenance. City of Plymouth Utilities and Minneapolis Water Works consistently deliver water meeting all Minnesota MDH and EPA Safe Drinking Water Act requirements.