In pseudo-homogenous pipeline flow of sand-water mixtures the measured hydraulic resistance is higher than for the flow of water, but is less than for a liquid having the same density as the mixture but a viscosity equal to that of water. A new analytical model is devised for pipe wall friction in which there is a watery viscous sublayer along the pipe wall. It is assumed that the presence of solids does not affect the viscous properties of the mixture, and that grain-stresses are negligible. A satisfying result is obtained in a particle range of 0.1 to 2mm median grain diameter and volumetric concentrations up to about 30%. It is found that the model describes a lower bound for hydraulic resistance. The theoretical concept can be used as a basis for further developments into the heterogeneous regime, where additional physical processes come into play.