Abstract: A flush water tank apparatus for storing flush water for flushing a flush toilet is disclosed. The flush water tank apparatus includes: a reservoir tank for storing flush water, the reservoir tank having a discharge port formed on the bottom surface thereof; a valve body for opening and closing a discharge port to supply flush water to a flush toilet; and a side surface extending in the upward direction from the bottom surface of the reservoir tank so as to surround the discharge port; and includes: a cylindrical body opens at the top and forms an opening portion on the side surface; and switching valves for opening and closing the opening portion on the cylindrical body to enable adjustment of the opening surface area of the opening portion of the cylindrical body so that the volume of flush water supplied from the reservoir tank discharge port to the flush toilet can be obtained in multiple stages, including at least the three stages of large, medium, and small.

Abstract: A flush water tank apparatus for storing flush water for flushing a flush toilet is disclosed. The flush water tank apparatus includes: a reservoir tank for storing flush water, the reservoir tank having a discharge port formed on the bottom surface thereof; a valve body for opening and closing a discharge port to supply flush water to a flush toilet; and a side surface extending in the upward direction from the bottom surface of the reservoir tank so as to surround the discharge port; and includes: a cylindrical body opens at the top and forms an opening portion on the side surface; and switching valves for opening and closing the opening portion on the cylindrical body to enable adjustment of the opening surface area of the opening portion of the cylindrical body so that the volume of flush water supplied from the reservoir tank discharge port to the flush toilet can be obtained in multiple stages, including at least the three stages of large, medium, and small.