SDF Rotary Filters are semi-automatic filters: Back-flush cleaning is maintained by opening a drain valve and rotating the filter’s body around its center-tube.
This design provides an infinite number of self-cleaning cycles, each made by a reverse flow of clean water (“back-flush”).

The SDF Rotary Filter is a permanent re-generative self-cleaning filter.

A fragmentary illustration of the Rotary Filter is seen on the right. The upstream dirty water is circulated to the exterior of the disks stack and infiltrated to the inner chamber, then the clean water downstream flows out via the other end of the center-tube. The rotating body is formed with peripheral cells, one of which is used for back-flush. Reverse flow is initiated by opening the drain valve while rotating the body to sweep the back-flush flow around all the disks. The reverse flow in the back flush cell is always of clean water that where first filtered by the other cells.

After a couple of turns the filter is completely cleaned. The disks remain tightened through the whole process and no gaps are opened any time.