Space Station Freedom (SSF) is required to distribute water for use and reprocessing. As SSF is erected, the configuration of the water distribution system changes along with specific functions. Therefore the interaction of the various components changes radically. Also, these components are taken off-line intermittently for maintenance (such as filter replacement). In order to analyze these interactions, a simplified steady state computer model was prepared. Parameters such as set points and storage tank capacities were revised based upon new performance understanding. The model was built using a Lotus 1-2-3 program. The model, making extensive use of macros, was iterated over thousands of hours of simulated SSF water processing in orbit. The data was stored and plotted. With the aid of the results of this modeling, the flight design was refined to a high level of maturity.