Pinellas County sits on a narrow peninsula between Tampa Bay and the Gulf of Mexico, and its water supply is unlike any other county in the region. Tampa Bay Water blends groundwater, surface water, and desalinated seawater to serve the peninsula, producing water that tests hard to very hard across most of the county. Largo's water hardness runs approximately 12.5 grains per gallon, and St. Petersburg measures around 9.5 grains per gallon, with Pinellas Park reaching even higher levels. The county's dense housing stock, which includes mid-century concrete block homes in St. Petersburg and Clearwater alongside newer construction in Palm Harbor and Dunedin, means scale buildup affects both old galvanized plumbing and modern appliances alike. Seasonal variation in the blended supply also causes water quality to shift throughout the year.