The present paper deals with clean pressure drop and power-law liquid across stacked-disc filters. Firstly, from mass and momentum (Darcy's law) balances the governing equations of the process are derived. Subsequently, these equations are reduced to a single dimensionless differential equation whose solution is governed by three dimensionless groups. Numerical and analytical solutions of the equation reveal the effect of these dimensionless groups on flow and related pressure drop. Finally, the theoretical model of the filter is found to be in good agreement with the performed experiments.