Hydro turbines used in hydroelectric power plants need to be designed and tested according to the specifications of the specific power plant, mainly the head and flow rate. Their models also need to be tested according to the standards provided by International Electrical Commission (IEC) before manufacturing the actual turbines. A Hydro turbine test rig at TOBB University of Economics and Technology is currently under construction to provide standardized tests for model turbines. A typical calibration system for a flow meter has four components; nozzle, flow diverter mechanism, weighing tank and load cells. The nozzle provides the regulation of water speed and supplies water to flow as a thin-sectioned profile. The flow diverter mechanism diverts the flow either to the weighing tank or to the reservoir. The flow rate is calculated from the collected mass and total time for the process. Calculated flow rate value is compared with the digitally measured values during the experiments, since the IEC standards require a real-time calibration for the flow rate. In this study, the flow diverter mechanism and the nozzle for this test rig is designed in order to meet several internationally acceptable standards.