Abstract: A calculation method of hydraulic losses in a vapor pump is proposed with reference to calculation method for high-speed centrifugal pumps. The pressure distribution in the collectors is determined by means of segmentation of flow together with pipe line, therefrom the radial force, pressure head and vapor core variation are found. Some numerical examples are also persented. The method can be applied either to estimation of the characteristics of a new pump in its preliminary design or to approximate evaluation of existing pumps.