Results of studies on water penetration into a model bed of glass balls 50 μm in diameter and three beds of silica flour with mean particle diameters 54, 24 and 17.7 μm are discussed in the paper. The tested silica flour beds had different values of standard deviation. In the tests a laminar macroscopic flow of liquid was analysed. It was found that geometry of a porous bed and properties of substances had an influence on the flow efficiency. With an increase of the bed height, water penetration rate into silica flour decreases, while for glass balls it increases. This provides evidence of structural changes in the bed during flow of water which covers particles with a liquid film and decreases friction coefficients, enabling displacement of fine particles in big voids, a decrease of porosity and an increase of flow resistance. The water penetration rate depends on particle size, wetted bed layer structure, bed height and porosity.