A water softener for reducing water hardness, suitable for use in a household washing machine, in particular a dishwasher, has a container within which ionic exchange resins are housed, which reduce the degree of hardness of water contacting them, and apparatus for regenerating the softening efficiency of the resins. Mounted in the container are a sensor for checking a physical characteristic of the resins and, in response thereto, detecting the degree of exhaustion of said resins.

A device for reducing water hardness suitable for the use in a household washing machine, in particular a dishwasher, comprising a container within which ionic exchange resins are housed, which provide to reduce the hardness degree of the water lapping them and means for regenerating the softening efficiency of said resins, wherein at least a portion of said resins are contained in a delimited space, a wall of said space comprises a movable or elastic element, means are provided for detecting the movement of said movable or elastic element.