A discharge valve device includes a valve body, an actuation shaft, a water storage cylinder, and a float, and from when the valve body opens to when the valve body closes, either flushing mode of a large flushing mode in which the flush water in a water storage tank is supplied from a discharge opening to the flush toilet in a first flush water amount or a small flushing mode in which the flush water is supplied in a second flush water amount smaller than the first flush water amount is selectively executable, and the water storage cylinder or the float is configured to change a lowering speed of the float with decrease in water level in the water storage cylinder depending on the selected large flushing mode or small flushing mode.

A flush valve assembly for a siphonic flush toilet, comprising a flush valve body and a flapper cover, wherein the flush valve body is coupled to an overflow tube or is coupled to an overflow tube coupling configured to receive an overflow tube, the flapper cover is configured to rotatably lift off the flush valve inlet at an open angle in a direction towards the overflow tube or the overflow tube coupling, and at least one of the flapper cover top face, the overflow tube, and the overflow tube coupling comprises a stop component configured to determine the flapper cover open angle during a flush cycle.

A toilet device (100), a flushing system (2) and a flushing method therefor. A control device (24) for the flushing system (2) controls the opening and closing of and opening and closing time of a first spray washing pipe (21) and a second spray washing pipe (22), and the emptying sequence of a toilet bowl (10), so as to form a plurality of flushing modes.