Abstract: A turbine assembly is for driving a pump of a fire extinguishing system, the pump being configured for injection of a chemical into a fire water column. The turbine assembly includes a housing provided with a flow channel extending therethrough for guiding at least a portion of the fire water column through the turbine assembly and a turbine wheel for being arranged in the flow channel. The turbine wheel includes turbine blades and two opposite side portions connected to and separated by the turbine blades. The turbine wheel is provided with openings between the turbine blades in order to provide at least one flow channel through the turbine wheel even when it does not rotate. The at least one flow channel through the turbine wheel starts between two turbine blades, runs through the turbine wheel, and ends between two other turbine blades.