A water sanitizing apparatus is provided wherein a housing is divided into separate narrow compartments through which a flow of water is directed sequentially in upward and downward directions. An ultraviolet ozone generator and pair of electrolysis plates are mounted in one of the narrow compartments, with a salt in the flow of water being electrolyzed to form a sanitizing halogen in the presence of ultraviolet light from the ozone generator. In one embodiment, a bubble separator is used to separate undissolved gasses from the flow of water and re-apply such gasses back to the flow of water upstream from the bubble separator.