A water treating device for a domestic water handling device such as a toilet water tank, an air conditioning drain pan or a humidifier includes a housing having permanent magnets in a flow path of water flowing through the housing via openings in the housing, to collect free ions in the water. An antimicrobial polymer disinfecting agent is in a mass inserted in a chamber in the housing and/or in a polymer in a housing surface. The housing is configured so an air bubble forms against the housing roof to assure that a base of the housing rests on the floor of the water handling device. Ribs adding structural strength to the cover are aligned and have approximately the same size and shape as slots in the cover roof through which water passes so the ribs obscure the magnets from view from above and to sides of the cover. The magnets are held in place by a spring finger extending upward from the base to exert a force downwardly against the magnet upper pole face.