A washing machine comprises a tub in which a drum is rotatably mounted, and a storage tank having a flow connection to the tub via a feeding line provided with a discharge pump and a three-port valve adapted to drive the flow to a drain or to the storage tank, rinsing fluid being stored in the storage tank for subsequent reuse. The washing machine further comprises an automatic valve connected to a drain line downstream the three-port valve and to an overflow line downstream the storage tank, said automatic valve being provided with means for avoiding any mixture of flows in the different configurations of the washing machine cycles.