A laundry treatment appliance comprising: - a water inlet configured to receive water from an external water supply; - a washing tub housing a rotatable drum adapted to receive laundry to be treated; - an apparatus for supplying process water into the washing tub; - a water softening system configured to receive water from the water inlet and to supply soft water to the apparatus for supplying process water into the washing tub, wherein said water softening system comprises: - a water softening agent container storing a water softening agent capable of reducing hardness of water, said water softening agent container having a first input fluidly coupled to the water inlet to receive water and an output to provide soft water obtained from the received water, - a water tank having an input configured to be selectively in fluid communication with said output of the water softening agent container and a first output in fluid communication with said apparatus for supplying process water into the washing tub, said water tank being configured for storing a reserve of soft water and for supplying with soft water said apparatus for supplying process water into the washing tub, - a container for storing salt, said salt container being configured to be selectively in fluid communication with a second output of the water tank for receiving soft water, characterized in that the salt container comprises an air vent duct configured to allow air inside the salt container exit the salt container by a pressure of soft water coming into the salt container from the water tank. - a water inlet configured to receive water from an external water supply; - a washing tub housing a rotatable drum adapted to receive laundry to be treated; - an apparatus for supplying process water into the washing tub; - a water softening system configured to receive water from the water inlet and to supply soft water to the apparatus for supplying process water into the washing tub, wherein said water softening system comprises: - a water softening agent container storing a water softening agent capable of reducing hardness of water, said water softening agent container having a first input fluidly coupled to the water inlet to receive water and an output to provide soft water obtained from the received water, - a water tank having an input configured to be selectively in fluid communication with said output of the water softening agent container and a first output in fluid communication with said apparatus for supplying process water into the washing tub, said water tank being configured for storing a reserve of soft water and for supplying with soft water said apparatus for supplying process water into the washing tub, - a container for storing salt, said salt container being configured to be selectively in fluid communication with a second output of the water tank for receiving soft water, - a water softening agent container storing a water softening agent capable of reducing hardness of water, said water softening agent container having a first input fluidly coupled to the water inlet to receive water and an output to provide soft water obtained from the received water, - a water tank having an input configured to be selectively in fluid communication with said output of the water softening agent container and a first output in fluid communication with said apparatus for supplying process water into the washing tub, said water tank being configured for storing a reserve of soft water and for supplying with soft water said apparatus for supplying process water into the washing tub, - a container for storing salt, said salt container being configured to be selectively in fluid communication with a second output of the water tank for receiving soft water,