Warning: GoldSim does not enforce a balance for the flow of the Reference Fluid in a Pipe.  That is, the Inflows into a Pipe do not need to be equal to the Outflows from the Pipe.  If the specified Outflows are greater than the specified Inflows, conceptually the effect on the species concentrations leaving the Pipe is one of dilution, since "clean" fluid is assumed to be flowing into the Pipe.  If, however, the specified Outflows are less than the specified Inflows, in the absence of decay and dispersion, the species concentrations leaving the Pipe would be greater than those entering the Pipe.  Conceptually, GoldSim would assume that a quantity of "clean" fluid (carrying no species mass) flowed out of the Pipe in order to conserve the flow rate and volume in the Pipe.  Although there are some physical situations in which you may actually want to do this (e.g., in order to simulate the evaporation of Water from a Pipe), typically such behavior would not be intended.  As a result, whenever the Inflows to a Pipe exceed the Outflows, GoldSim provides a (non-fatal) warning message to the Run Log.