PURPOSE: To prevent inconvenience caused by stoppage of steady flow pump due to power interruption, by feeding compressed air from a pressure source into an auxiliary tank upon stoppage of water transportation pump thereby discharging water from the backup tank.

CONSTITUTION: Under normal condition, a water transportation pump 9 will cause steady flow through a check valve 8 into the system to fill the backup tank 6 with water. Upon stoppage of pump due to power interruption, a valve 7 will open automatically to flow compressed gas from a pressure source 13 into the backup tank 6 thus to pressurize the inside of tank. Consequently, the water in the tank will flow into the steady flow transportation pipe 10. Upon complete discharge of water from the tank, a float will function to choke the outlet thus to prevent flow-out of compressed gas.