A backflush filter device for filter elements is incorporated in a filter housing having a filter inlet and an outlet for the liquid to be filtered. Row crops between the closed walls are shielded from extreme conditions including frost, heavy rain, freeze, hail, and winds. In a pump, a compressor and an externally heated engine, the selective movement of the pistons always maintains a piston between the two ports. The controller is disposed at the proximal end and provides enhanced control of the distal tip of the elongated body.