PURPOSE: To prevent the drainage of the high pressure air by draining the leak water into a draft tube through a plurality of conduits from a guide vane which is closed when the runner submergence is pushed down in the phase adjustment operation and selectively opening and closing a valve which is installed in each conduit and has a mutually different large or small bore.

CONSTITUTION: A hydraulic machine is equipped with guide vanes 2 and 2 on both sides on the inlet side of a runner 4, and equipped with a suction pipe 5 on the outlet side, and in the phase adjustment operation, the guide vane 2 is closed, and high pressure air is supplied into a runner chamber 3, and the submergence in the runner 4 is pushed down to a draft tube 5. In this case, conduits 6a and 6b having the first and second valves 10 and 11 each having a large diameter are installed between the guide vane 2 and the draft tube 5. Further, conduits 7a and 7b having the third and fourth valve 8 and 9 each having a small diameter are installed between the lower covers 4a and 4b of the runners 4 and 4 and the draft tube 5. Each of valves is 8-11 is selectively opened and closed according to the high or low state of the pressure field in the runner chamber 3, when the leak water is drained into the draft tube 5 from the guide vane 2 which is closed in pressing down operation.