The $3.9B global cooling tower industry extracts heat from industrial, commercial or municipal systems through the process of evaporation. Hot water is pumped into the cooling tower where it cascades over layers of vertical and horizontal splash elements surrounded by continuously moving air. As water is recirculated from the cooling tower to be reused in the process, additional water must be periodically added to replace the portion of water that has evaporated. The main causes of evaporation are drift (droplets carried from the tower in the exhaust air), blow-out (droplets blown out of the tower by gusty winds), plume (vapor that condenses and rises out of the tower) and blow-down (the amount of water removed to maintain an acceptable percentage of dissolved solids). Evaporation or the need for make-up, is determined by measuring the water level in the cooling tower basin or adjacent sump. When the level falls to a low level set point, the PLC will open the fill valve until the water reaches a high level set point. The make-up process can occur hourly or daily based upon demands on the system, local climate and time of year. At this thermo-electric power station, an EchoSonic ultrasonic level transmitter is installed in each cooling tower sump. The non-contact sensor was selected for its reliable, maintenance-free operation and corrosion-resistant packaging.