A water powered sump pump has a control housing connected to a source of water under pressure and to a drain pipe located in a sump. An outlet pipe leads from the control housing to a suction generating assembly in communication with the drain pipe for entraining water from the sump for discharge elsewhere. A diaphragm closure normally closes a water passage in the housing and divides the housing into two chambers. A passageway through the diaphragm enables the pressure of water in the two chambers to be equalized. A bleed line communicates between one of the chambers and the sump. A valve responsive to the rise of water in the sump initiates the flow of water through the bleed line, thereby enabling lowering of the pressure in the chamber with which the bleed line communicates and enabling the pressure of water in the other chamber to unseat the diaphragm and open the passage.
