The article describes filtration investigations on a laboratory scale by the use of a pressure test filter. It enables the estimation of filtration constants, compressibility coefficient of the final product and dewatering in a cake compression zone. A method of experimental treatment of data was proposed for particular slurries based on constants K or modified constants K’ of the characteristic filtration equation. The use of a pressure test filter makes it possible to reduce the investigation time, reduce the costs and approximate the results for other process conditions.