An advanced on-site water sanitization system is taught having integrated chlorine generation and copper/silver ionization in the same unit. The system includes a manifold loop connectable to a water supply line for supplying water to be sanitized from a body of water, and connectable to a water return line for returning sanitized water to the body of water. It also includes a copper/silver ionizer, capable of receiving a flow of water to be sanitized, adding copper and silver ions to the flow of water so as to provide a copper/silver ionized flow of water. A chlorinator is also included, capable of receiving a flow of ionized water, and a flow of chlorine, and allowing the flow of chlorine to mix with the flow of ionized water so as to provide a chlorinated flow of ionized water to the manifold loop to return as sanitized water to the body of water.