The results of the analysis of methods for calculating the parameters of hydraulic transporting polydisperse slurries containing particles of different sizes, which predetermines significant difficulties in selecting the critical flow rate and determining the corresponding head losses, are presented. To a large extent, the parameters of hydraulic conveying of slurries depend on the value of the relative flow velocity of solid and liquid phases. One of the calculation methods is grapho-analytical, based on the results of experimental studies of the process and theoretical regularities. It is proposed to calculate the head loss during hydraulic transportation of heterogeneous materials using Mohlerus-Wellman nomograms, obtained experimentally for the relative flow velocity of the two-phase polydisperse slurry.