(57) An obturator device for the tub of a laundry washing machine comprising a tub housing the drum containing the laundry to be washed and having its bottom portion formed with a port forming a seat for an obturator element coupled to a cinematic transmission mechanism advantageously actuated by a solenoid connected to the discharge pump for energization in synchronism therewith, so that during the initial phases of the washing operation the water and the detergent supplied thereto are exclusively utilized forthe washing operation, without any portion of the solution flowing into the discharge circuit disposed below the level of the tub and only accessible during operation of the discharge pump.