Keystone Water Hardness & Quality Report (2026)

Keystone, Florida, in Hillsborough County in the semi-rural northwestern sector near the Pasco County border, receives its municipal water from Hillsborough County Water Department or local community water systems, drawing from the Upper Floridan Aquifer through wells in the northwestern Hillsborough County area. Keystone is a less densely developed community in the transition zone between the Tampa urban core and the agricultural and conservation lands of northwest Hillsborough and Pasco counties, and it relies primarily on the deep Floridan Aquifer for water supply rather than Tampa Bay Water's blended regional system.

The very hard 271 mg/L hardness and high TDS of 848 mg/L reflect the Upper Floridan Aquifer's deep carbonate character in the northwestern Hillsborough reach. Unlike the Tampa Bay Water coastal supply (which is treated and moderated through desalination blending), the Upper Floridan Aquifer in the inland northwestern Hillsborough zone taps deep Eocene Avon Park Formation dolomite and overlying Suwannee Limestone — ancient tropical marine carbonate formations that have been circulating groundwater for millions of years. This extended circulation through pure dolomite and limestone formations produces water with very high calcium and magnesium concentrations. The elevated TDS of 848 mg/L reflects the combination of carbonate hardness and deep aquifer mineral loading.

At 271 mg/L, Keystone residents deal with very hard water from a deep Floridan supply that is considerably harder than Tampa's treated coastal supply. Scale forms rapidly in kettles and coffee machines within weeks, dishwashers require water softener treatment to produce acceptable glassware, and bathroom glass and tile develop persistent calcium deposits. Descaling appliances every four to six weeks is appropriate. A whole-house water softener is strongly recommended for Keystone households. The elevated PFAS level of 11.1 ppt adds urgency — a certified reverse osmosis unit is the most practical solution for both the extreme hardness and PFAS concerns in daily drinking water.