High pressure water jets are used to remove scale from the steel bars before they enter the rolling mill. The descaler pump runs at constant speed, and the high pressure water is bypassed to the water pit when no bar is present. Running the pump at constant speed wastes energy and water, and heavy maintenance is required on the motor, bypass valves, and the pump. If the roughing mill is reversing, there are descale nozzles on either side, using even more energy. A solution is to use a variable frequency drive on the pump to reduce the flow when the bar has left the descale area, thus reducing the load on the motor and the energy consumption.