Water sanitizing apparatus is provided for pools, spas hot tubs and other similar bathing facilities that integrates an ozone generator and a chlorine generator in one unit, in addition to exposing a flow of water to be purified to ultraviolet radiation from the ozone generator for advanced oxidation reactions. In one embodiment, a mixing venturi allows for mixing various substances together prior to insertion into the motive flow. In another embodiment the venturi is constructed as inserts that allow tuning of the venturi for individual systems. In other embodiments, salt is added to a portion of the water flow as a concentrated brine from which chlorine is generated, or the salt may be simply be added to the water of the facility at a much lower concentration and chlorine generated from the flow of water through the apparatus.