The invention relates to an unpowered floating drum type water decanter. The unpowered floating drum type water decanter comprises a corrugated tube (3) arranged between a floating drum (1) and a water outlet tube (2); and the outer wall of the corrugated tube (3) is provided with a guide rod (4) axially parallel to the corrugated tube (3), and the water outlet tube (2) is provided with a spacing plate (5) for supporting the guide rod (4). The upper part of the corrugated tube is provided with a closed space filled with a damping medium, and the damping medium provides certain damping force for the corrugated tube when the corrugated tube is easily damaged due to the non-uniform deformation of all parts of the corrugated tube, caused by large deformation amount of the upper part and small deformation amount of the lower part due to primary deformation of the upper part of the corrugated tube in the ascending or descending process of the corrugated tube, so a part of the deformation amount of the upper part of the corrugated tube transmits to the corrugated tube, the deformation uniformity of all parts of the corrugated tube is guaranteed to a certain degree, and the service life of the corrugated tube is prolonged.