Vortex filters (also known as swirl filters) work through centrifugal action. Water enters the top of the main chamber tangential to its cylindrical surface at high velocity, sufficient to maintain cylindrical whirlpool flow. The centrifugal effect forces heavier particulates to the outside walls, eventually collecting in the bottom, while the separated water drains to the center pipe running down the cylinder's axis, with its opening slightly below the level of the entrance jets.