The present recreational vehicle water warming and circulating system uses the heated water in the water heater to heat the on-board water supply when the outside air temperature drops below the freezing point of water. The system includes a holding tank for containing a majority of the on-board water supply, and heated and cold loops that supply heated and cold water to various fixtures in the recreational vehicle. When temperature sensors sense a potentially freezing condition, a control circuit opens one or more solenoid valves to open the one or both loops to return undispensed heated or cold water to the holding tank. The control circuit closes the solenoid valves when the potentially freezing condition is no longer detected by the temperature sensors.