This phenomenon occurs when a portion of the debris in the pool consists of fine, dust-like particles. After exiting through the filter discharge outlet, these particles quickly become suspended in the water and are subsequently removed by the filtration system.
Most filter screens used in automatic cleaning devices are typically rated at around 80 mesh, which allows them to effectively capture larger debris without difficulty.
However, the filtration behavior of fine dust differs significantly. Such particles are easily agitated and remain suspended in the water; the automatic cleaner primarily serves to stir them into suspension, after which they are captured by the filtration system.
This process can result in improved overall cleaning efficiency. At the same time, it explains why automatic pool cleaners cannot currently serve as a complete substitute for dedicated filter pumps.