It has been shown that the transport of a free solvent through ion-exchange membranes of different structural types in NaCl solutions can be calculated within the framework of the capillary model for electroosmotic transport on the basis of data on pore-radius distribution, exchange capacity, internal specific surface area, and concentration dependences of membrane electrical conductivity. The electrolyte-solution concentration range has been determined in which the convergence is observed between the data calculated in terms of the model and the results of the independent experimental determination of the numbers of water transport through the membranes. The fraction of through pores in the structure of an ion-exchange membrane has been found, and it has been shown that this fraction depends on the structural type of a polymer film alone.