Distillation columns frequently produce both vapor and liquid distillate product streams from the reflux drum when the feed stream contains small amounts of light components that would require high pressures or low temperatures if a total condenser were used to completely condense the overhead product. Since removing heat using cooling water in the condenser is much less expensive than using refrigeration, many columns are designed to operate with reflux-drum temperatures of about 120 degrees F so that cooling water at 90 degrees F can be used. Fixing reflux-drum temperature and selecting a reasonable pressure determines the split between the amount of vapor product and the amount of liquid product. In the operation of these systems, we usually want to condense as much as possible so as to minimize compression costs of dealing with the vapor product. Therefore the flow rate of cooling water should be maximized. This paper demonstrates a realistic way to model a partial-condenser distillation system using Aspen simulation.