Green Bay Water Hardness & Quality Report (2026)

Green Bay Water Utility serves approximately 100,000 customers across the City of Green Bay and surrounding areas in Brown County, Wisconsin. The sole potable source is Lake Michigan, drawn through intake cribs in Green Bay harbor. Raw water is treated at the David L. Puffer Water Filtration Plant, which processes lake water through screening, coagulation, sedimentation, filtration, and disinfection. No groundwater or river sources are used for potable supply, making this an entirely surface water system dependent on Great Lakes resources.

The supply originates from the Lake Michigan watershed, part of the Great Lakes Basin spanning multiple states. Paleozoic carbonate rock formations — including Ordovician dolomites and Silurian limestones — underlie the basin, with glacial drift deposits shaping surficial hydrology. As surface water, Lake Michigan experiences limited rock-water interaction, yielding a moderately mineralised character from natural bicarbonates leached during transit through limestone terrains and glacial till, rather than the high mineralization typical of deep groundwater aquifers in carbonate or sandstone formations.

Moderately hard water at 130 mg/L promotes moderate scale buildup in pipes, water heaters, and dishwashers, potentially reducing efficiency over time. Boilers and washing machines are also susceptible to limescale shortening their lifespan if unaddressed. Regular maintenance — deliming fixtures and flushing heaters — is advised. A water softener is recommended for households noticing soap scum, dry skin, or spotting on glassware. Water quality complies with EPA standards including lead and copper rule adherence; recent PFAS monitoring under the Fifth Unregulated Contaminant Monitoring Rule detected PFOS at 2.13 ppt, well below the 4.0 ppt limit. No notable contaminants exceed health guidelines.