A filter device for filtering a liquid portion by passing it through a filtering medium, comprising a cartridge with a treatment region filled with a filtering medium, an inlet and an outlet for liquid. The cartridge comprises a first array of walls arranged in the treatment region defining an array of spaces in between said walls for the liquid successively flowing through said spaces into a tubular vessel at the liquid outlet, the dimensions of said tubular vessel being selected to create an effect of communicating vessels within said array of spaces, to maintain a part of the filtering medium in liquid environment.
The filter device also comprises a locking mechanism located within the liquid flow path through the cartridge and configured to block the liquid inlet and/or outlet upon expiration of life time of the filtering medium, comprising an erodible member and a mechanical assembly coupled to said erodible member and shiftable from its unlocking positions into its locking position.