The froth phase is extremely important in the operation of a flotation cell, seeing that -it is critical in determining the amount of unwanted gangue collected to the concentrate and thus the purity of the product. This paper uses a fundamentally based model of flowing froths to simulate the performance of a flotation cell. The study concentrates specifically on the effect of wash water addition on the overall performance, i.e. the grade and the recovery, The froth model that is used within this work includes a large number of the effects seen within a flotation froth and approaches their description from a fundamental point of view. Some of the phenomena that are included are bubble coalescence, liquid drainage including the effects of gravity, surface tension and viscous dissipation, particle settling and particle dispersion. The results show the advantages and disadvantages of different water addition strategies on the performance of flotation vessels. Since most recent flotation work has been concerned with improving recoveries, rather than grade, the addition of water into flotation froths has been largely limited to column cells. This work demonstrates how water addition can be optimised in terms of both water addition point and quantity in order to produce the desired performance.