Abstract: The present invention provides a gravity fiber filter, comprising: a filter tank placed in a portion of a large amount of running water; at least one unit filter disposed in the filter tank; a filtered water collecting tank disposed in a lower portion of the filter tank; a discharging pipe extended from the filtered water collecting tank to the height lower than a influent inlet of the filter tank, so that the height of the extended discharging pipe is defined as a height of starting filtration; a sensor; a air inflow pipe through which a backwash air flows in from outside to a lower portion of the filter tank; a control means controlling the operation of filtering and backwashing; and backwash water discharging pipe.

Abstract: The pore size controllable filter can separate and remove effectively the suspended solid and eliminate rapidly it captured by the device. The filtering materials (21) are built on the upper filtering material holder (23) and the lower filtering material holder (24) of radial type facing each other at a certain distance in the filtering tub (2), forming a filtering layer (21a). According to the direction and the degree of rotation of the upper handle (28) connected to the upper rotation axis, the filtering materials (21) come together to the center along the upper filtering material holder (23) and the lower filtering material holder (24). Then one side or both sides are twisted in opposite directions and concentrated around the perforated pipe (22) located at the central axis or restored to the original state. Accordingly, the size of the pore created between the filtering materials (21) can be adjusted, enabling to conduct filtering and washing operations at a proper level.