PURPOSE: To practically eliminate the possibility of water being decayed and prevent the production of algae by providing a number of spherical far-infrared radiating bodies based on alumina, silica, zirconia, magnesia, titania, etc., throughout a circulating water passage.

CONSTITUTION: Basic materials, i.e., alumina, silica, zirconia, magnesia and titania are mixed with other effective materials and this mixture is thereafter baked to obtain spherical far-infrared radiating bodies. Such spherical bodies in different sizes are combined in desired volume proportions to impart the radiant property of the far-infrared rays in order to permit raw water to be changed into an active water as easily usable as desired in addition to the adsorbing property required of filtration. The spherical far-infrared radiating bodies can also be used in large, medium and small sized pure water producing device or unpure water activating device or for the pretreatment or treatment of the pure water producing device.