VLEACH is a simple one-dimensional vadose zone leaching model capable of simulating volatile chemical transport. There is no explicit dispersion coefficient in VLEACH. Solutions computed with it show dispersion due to diffusion in the gaseous phase and its interaction with the liquid phase and also due to the discretization of the problem domain. By turning off gaseous diffusion and comparing VLEACH results to the standard convection dispersion equation, this Computer Note illustrates that the effective dispersivity due to the discretization is equal to half of the model cell size.