A system for extracting a liquid by pressing a humid mass, the system including at least one extraction channel, while extraction channel being provided with at least one inlet allowing to feed the extraction channel with the humid mass to be treated; with walls provided with holes allowing the flow of the liquid contained in the humid mass being pressed, and with at least one outlet allowing the discharge of the dehydrated mass obtained by pressing in the extracting channel, wherein the outlet of the channel, positioned between the walls provided with holes and the exterior, is free of contraints or only includes weak constraints whose level is controlled as a function of physical parameters. This systems is suitable for the efficient continuous dewatering treatment of a feeding source with a composition, consistency and nature of the solid particles present in the feeding source susceptible to vary during the processing.