PURPOSE: To raise water with a pump in connection with a hot water boiler, cold water condenser, piston drive chamber, and control valves therefore, by returning the working medium liquid from the condenser to boiler by means of its own gravity, and by sucking the liquid situated in lower place directly into the piston chamber.

CONSTITUTION: When a certain specific amount of the working medium liquid is accumulated in a condenser 5, valves 7, 8, 9 are opened to return it quickly to a hot water boiler 1. Then said valves 7, 8, 9 are closed. The high pressure steam of said working medium produced at said hot water boiler 1 is injected into a piston drive chamber 3 by opening the valve 7 to cause rightwise motion of piston 4. Thereby the liquid filling the righthand chamber is extruded out from a pipe 13. Then the valve is closed and valve 8 opened to allow condensation of the working medium steam in the lefthand chamber of piston 4 at the abovementioned condenser 5, to cause pressure drop on the left side of piston 4, and now the piston 4 moves to the left to shut a check valve 14, so that the liquid moves from lower liquid trough 12 into the righthand chamber of piston 4 via pipe 10. Now the valve 8 is shut. Repetition of this operation will allow pumping-up of the liquid by a minor power.