Patent ID: 8720480

Claim:
A flush water supply device for supplying flush water to a flush water tank of a flush toilet, comprising: a water supply pipe having an upstream end connected to an external water supply source and extending upwardly from a bottom wall of the flush water tank; a water supply valve for switching between a water supplying state and a water stopping state with respect of an inside of the flush water tank, in terms of flush water supplied from the water supply pipe; a refill water section provided on a downstream side of the water supply valve and adapted to allow flush water supplied from the water supply valve to be supplied to the flush water tank, and further supplied to a toilet main body of the flush toilet as refill water, the refill water section including a common passage-forming portion which forms a common passage having: an inlet port for allowing therethrough inflow of flush water passing through the water supply valve; a tank-side outlet port for allowing flush water inflowing through the inlet port to flow out toward the inside of the flush water tank therethrough; a main unit-side outlet port for allowing flush water inflowing through the inlet port to flow out toward the toilet main body therethrough; and a vent port formed just above the inlet port and communicated with outside air; and a vacuum break valve provided in the common passage-forming portion, the vacuum break valve having a valve element for opening and closing the common passage, and a valve element holding member adapted to be guided in an up-down direction by an inward wall partially defining the common passage, while clamping the valve element, wherein the valve element of the vacuum break valve is adapted to be movable between the inlet port and the vent port of the common passage in the up-down direction by a given distance.