A non-adjustable water pressure and flow speed regulating flushing system includes a valve member adapted for sealedly disposing between the water inlet and outlet to control water flowing from water inlet to outlet through the water chamber, a relief valve disposed within the water chamber for controlling the water flowing from water chamber to water outlet, and a flow speed regulation arrangement which includes an elongated bleed channel for controlling a water pressure between the water inlet and water chamber, so as to regulate a flow speed of the water entering into the water chamber through the bleed channel in a non-adjustable manner.