While overall water quality throughout the City of Covina service area is very good, operators struggled with one section of their distribution system that was fed from a 5 MG underground tank. Disinfectant residual levels entering the tank were typically around 1.0 ppm, but water leaving the tank had only 0.5 ppm of disinfectant residual or less. The Covina team hired a diver to install the PAX Water Mixer in the center of the 5 MG tank. After turning the unit on, operators at Covina saw their thermal stratification problem disappear. Completely mixed conditions were established after only a few hours and residual levels inside the tank improved dramatically.