The study outlines technical solutions for measurement of water mass stream flowing from cooling towers to steam condensers. Such solution was applied in 200 MW power units of condensing power plants. Two methods were used for these measurements: probes averaging dynamic pressure and flowmeters using the forces of inertia in fluids resulting from a change in the flow direction or the so called elbow flow meters. The flow coefficient value found to be 7.01 for the flow meter under consideration. Also, the study presents the methods of measurements, metrological properties of flowmeters and measurement uncertainty analysis. At α = 0.95, the uncertainty of volumetric stream measurement, at stable flow of water stream and for differential static pressure over 50 Pa, quickly approaches 2.30%.