One embodiment of the present application relates to a water tank for a toilet. The water tank includes a first chamber comprising an orifice for connecting to a toilet bowl. The water tank further includes a free-floating member within the first chamber that is not coupled to any other component and that is configured to selectively engage with and disengage from the orifice to selectively block or allow a flow of water through the orifice. The free-floating member can be selectively disengaged from the orifice via an actuator or a differential pressure within the water tank.