Why is Sand Blowing Out of a Pool Filter? | Hunker
Sep 19, 2017· A sand filter is basically a large tank filled with poolgrade sand, which is coarser than regular play sand. Water enters the tank through an inlet at the top, and gravity pulls it downward, removing impurities that get lodged in the sand. At the bottom of the tank, the water enters the laterals, which have tiny perforations that keep out the sand.