A system for sanitizing and refilling a potable water system onboard a transport vehicle includes a potable water supply conduit, a potable water feed conduit, a potable water return conduit, a drain conduit, and a sanitizing and refilling station wherein the system is operable in a self-flush mode, a sanitizing mode using ozone, and a fill mode. A method of sanitizing and refilling a potable water system onboard a transport vehicle includes the steps of purging stagnant water from a sanitizing and refilling station, draining stagnant water from the transport's potable water system, sanitizing the transport's potable water system using ozone, draining the transport's potable water system, and filling the transport's potable water system by delivering fresh water.