The invention relates to a line system for a water power plant, comprising the following features and components: a turbine having a turbine impeller and a turbine spiral housing, a pump having a pump impeller and a pump spiral housing, the two spiral housings being arranged to run in opposite directions to one another, a shaft on which the turbine impeller and the pumpkin impeller are arranged in a rotationally fixed manner, an electric machine that has a drive connection to the shaft or can connected thereto, the pressure lines of the two spiral housings opening in a common line pressure line, a turbine pressure line for introducing water out of the main pressure line into a pump turbine in turbine operation, a pump pressure line configured as a bend for introducing water out of the pump turbine into the main pressure line in pump operation or back through the turbine pressure line to the pump turbine in a hydraulic short circuit, and a branch part to which the main pressure line, the turbine pressure line and the pump pressure line are connected. The invention is characterized by the following features: the flow cross section of the bend is larger at the outlet therefrom than at the inlet thereto.