Two polypropylene hollow-fiber membranes with quite different porosities and gas permeation rates were encapsulated as U-configuration modules, and their filtration properties were evaluated with the method of dead-end tap water filtration. The filtration processes were described by filtration cake theory. At the beginning of one operation period, the resistance of the membrane dominated the permeation, the permeation rate decreased quickly with time, and the resistance of the filtration cake increased linearly with overall permeation volume. Initially membrane flux did not vary apparently as much as when the resistance of the filtration cake almost achieved that of the membrane. The analysis results indicate that, under the same specific permeation volume, the resistance of filtration cake increased in relation not only to the properties of a treated solution, but also to the properties of microporous membrane materials.