Mendota Heights Water Hardness & Quality Report (2026)

The South St. Paul Residential Water Service provides water to Mendota Heights, Minnesota, drawing from groundwater wells that tap into aquifers in Dakota County. These wells access both the Quaternary glacial drift and deeper bedrock formations, including the significant Jordan Aquifer. The water is treated at wellhead facilities with disinfection and corrosion control before distribution to about 10,000 connections. While the supply is within the Vermillion River sub-watershed of the Upper Mississippi River Basin, its groundwater origin means it has limited interaction with surface water.

The geology beneath Mendota Heights consists of glacial till, sands, gravels, and the Cambrian-Ordovician sandstone aquifers. These bedrock layers, notably the Jordan Aquifer and Oneota Dolomite, are rich in Paleozoic-era limestone and dolomite. As water filters through these formations, it dissolves calcium and magnesium ions, resulting in a mineralized, hard water supply. This characteristic is typical of groundwater sources in glaciated regions of east-central Minnesota.

Homeowners in Mendota Heights may notice accelerated scale buildup in appliances like water heaters and dishwashers, which can reduce efficiency and shorten their lifespan. Frequent cleaning of faucet aerators and showerheads might become necessary due to clogging. To manage the mineral content, monthly vinegar flushes for fixtures and annual descaling of water heaters are advised. Installing a water softener is strongly recommended to prevent spotting on glassware, alleviate dry skin, and protect plumbing from damage. The SPRWS water, while hard, is treated with corrosion inhibitors and meets EPA standards, with primary treatment including chlorination and fluoride addition.