An up-flow filter has four layers of filtration media, each of different size and density

Fine media (1.6 mm) lies at at the top of the filter bed.  Media become progressively larger in the lower layers.

Larger suspended particles are removed by the lower layers while smaller particles are removed in the upper layers

Particles are trapped throughout the bed, not in just the top few inches.

Runs substantially longer and uses less backwash water than a traditional sand filter

Uses air for back-wash bed agitation, reducing water requirement further