Modeling pumps in 1D flows in Modelica is not new. In this paper a new approach is presented that can be used for general centrifugal pumps as well as centrifugal pumps based on measurement data for the DLR Thermofluid Stream Library. The presented model is based on dimensionless numbers for good scaling. This approach allows to predict the pump behavior also for pumps where no measurement data exist based on data from similar pumps. The models are designed with focus on numerically robustness. They avoid non-linear equation systems and work for zero mass flow rate and/or zero angular velocity. Furthermore care has been taken that extrapolation of the pump data outside the data range is robust without interpolation artifacts. A pump surge example demonstrates that the TFS can handle instationary behavior like limit cycles by default without any further modifications needed.