Abstract: The present invention relates to a device for conditioning water containing calcite and an installation constructed with this device. This device essentially comprises an inner tubular element (10), an outer tubular element (11) and two end tips (12 and 13). These elements are arranged so as to provide an annular space (18) between the tubular element (10) and the tubular element (11). The inlet tip (12) comprises a central hole (19) and at least one lateral opening for providing communication of the central hole with the annular space (18). The outlet tip (13) comprises a central hole (21) and at least one lateral opening for receiving the water circulating through the annular space (18). The lateral opening or openings of the inlet tip are arranged so as to develop a helicoidal circulation of the water in the annular space (18) whatever the operating rate may be.