A new filtration model has been developed to describe the entire three-stage filtration run. The two-stage assumption is applied for physical description of the rapid gravity filtration process. At the first stage of the filtration, previously deposited particles serve as collectors to improve particle removal efficiency and the detachment of deposited particles does not occur until the specific deposit reaches a certain transient specific deposit where the second stage starts. Particle detachment rate at the second stage is assumed to be a function of relative specific deposit and hydrodynamic conditions within filter media. The proposed filtration model has been applied to fit the data from one water treatment plant of Yorkshire Water (UK). The comparison demonstrates a good agreement between water treatment site data and the simulated results.