Abstract: A water-saving device for toilets is provided which when employed in a conventional toilet tank allows for flushing a conventional toilet employing an amount of water which is substantially less than usually employed. The water-saving device of the invention employs a combination of a lower float and an upper float; upon flushing, the lower float functions as a closure member for the orifice in the bottom of the toilet tank and the upper float is adapted to bear against the lower float to force the lower float to seat in the orifice of the tank after the level of water in the tank has been reduced to 75% or less of the water normally used in flushing a toilet. In addition, locking means and related control means are provided for releasing the upper float when the toilet is flushed and for locking the upper float in an immobile position when the flush has been effected.