An admixing system for fire extinguishing systems for producing an extinguishing agent / extinguishing agent additive mixture -premix- by admixing an extinguishing agent additive, in particular a foaming agent, to an extinguishing agent, in particular water, comprising - a motor, in particular a water motor, able to be driven by a flow of extinguishing agent which has an inlet for supplying the extinguishing agent to the motor, in particular from an extinguishing agent tank or from an extinguishing agent supply line, an outlet for discharging the extinguishing agent from the motor, and an output shaft able to be driven by the motor, - an admixing pump for conveying the extinguishing agent additive which has an input shaft coupled to the output shaft of the motor, an input for providing the extinguishing agent additive, in particular from an extinguishing agent additive tank or from an extinguishing agent additive supply line, and at least one output (8a, 8b) for discharging the extinguishing agent additive conveyed by the admixing pump, - an extinguishing agent additive inlet line having a first inlet-side end and a second pump-side end, wherein the pump-side end is fluidly connected to the input of the admixing pump, - an admixing line having a first motor-side end and a second outlet-side end, wherein the motor-side end is fluidly connected to the outlet of the motor, - an extinguishing agent additive outlet line having a first pump-side end and a second admixing line-side end, wherein the pump-side end is fluidly connected to the at least one output of the admixing pump and the admixing line-side end is fluidly connected to the admixing line at an admixture point, characterized in that the admixing pump is a piston pump, particularly a plunger pump, which has a plurality of cylinders and at least two outputs (8a, 8b), wherein each output (8a, 8b) is fluidly connected to at least one cylinder and each cylinder is fluidly connected to exactly one output (8a, 8b), and that the admixing system further comprises a return flow line having a first pump output-side end and a second pump input-side end, wherein at least one first return-flow-capable output of the admixing pump can be switched via a switching device to either be fluidly connected to the pump output-side end of the return flow line or to the pump-side end of the extinguishing agent additive outlet line; the other outputs of the admixing pump, which are not capable of return flow, are fluidly connected to the pump-side end of the extinguishing agent additive outlet line; and the pump input-side end of the return flow line is fluidly connected to the extinguishing agent additive inlet line or to the input of the admixing pump. - a motor, in particular a water motor, able to be driven by a flow of extinguishing agent which has an inlet for supplying the extinguishing agent to the motor, in particular from an extinguishing agent tank or from an extinguishing agent supply line, an outlet for discharging the extinguishing agent from the motor, and an output shaft able to be driven by the motor, - an admixing pump for conveying the extinguishing agent additive which has an input shaft coupled to the output shaft of the motor, an input for providing the extinguishing agent additive, in particular from an extinguishing agent additive tank or from an extinguishing agent additive supply line, and at least one output (8a, 8b) for discharging the extinguishing agent additive conveyed by the admixing pump, - an extinguishing agent additive inlet line having a first inlet-side end and a second pump-side end, wherein the pump-side end is fluidly connected to the input of the admixing pump, - an admixing line having a first motor-side end and a second outlet-side end, wherein the motor-side end is fluidly connected to the outlet of the motor, - an extinguishing agent additive outlet line having a first pump-side end and a second admixing line-side end, wherein the pump-side end is fluidly connected to the at least one output of the admixing pump and the admixing line-side end is fluidly connected to the admixing line at an admixture point, the admixing pump is a piston pump, particularly a plunger pump, which has a plurality of cylinders and at least two outputs (8a, 8b), wherein each output (8a, 8b) is fluidly connected to at least one cylinder and each cylinder is fluidly connected to exactly one output (8a, 8b), and that the admixing system further comprises a return flow line having a first pump output-side end and a second pump input-side end, wherein at least one first return-flow-capable output of the admixing pump can be switched via a switching device to either be fluidly connected to the pump output-side end of the return flow line or to the pump-side end of the extinguishing agent additive outlet line; the other outputs of the admixing pump, which are not capable of return flow, are fluidly connected to the pump-side end of the extinguishing agent additive outlet line; and the pump input-side end of the return flow line is fluidly connected to the extinguishing agent additive inlet line or to the input of the admixing pump.