How is splash water caused in the toilet?

One reason for the occurrence of splash water is the size of the flushing channel. Each flushing process creates a gush of water, which traps air and entrains it. Due to the uplift, the air bubbles entrain water particles upwards, thus causing the splashing effect. A further reason lies in the surface tension of the flushing water, which is influenced by the water hardness. Cistern manufacturers offer flush flow restrictors, dependent on the model type, by means of which the dynamics of the flushing process can be optimised. Slight splashing, however, is unavoidable and by reason of the aforementioned causes not a defect.