Filtration is the separation of solid–liquid mixtures. In this study, we assess the predictive power of Kozeny–Carman model for systems operated at low Reynolds numbers and relatively high pressure drops. We find substantial agreement between the K‐C model and experiment only for systems that exhibit tight void size distribution. Dramatic disagreement is observed for particle beds that exhibit wide void size distributions. We propose a modified modeling approach, based on a bimodal void distribution, by introducing two quantities: the fraction of expanded voids and the ratio of void sizes. The simulation results are found to be much more similar to the experimental flow rates than those calculated using the K‐C model. The modified model is deemed reliable at predicting the flow behavior, provided that an accurate representation of the void size distribution is available.