An additive dispenser includes a fluid-retaining chamber. A siphoning post extends upward from a lower surface of the fluid-retaining chamber and cooperates with a cap or other structure so as to form a siphon chamber. When water is added to the chamber and a liquid level rises above an inlet to the siphoning element, a siphoning effect draws fluid from the chamber. When the siphoning effect is interrupted, any unsiphoned fluid remaining in the chamber exits by permeation through one or more porous elements located in a base of the chamber.