Abstract: A livestock watering system is provided which is adapted to selectively circulate water in a basin in response to temperature differentials of the water in a lower reservoir portion of the basin and an upper drinking portion of the basin utilizing a thermal-siphon phenomenon. The livestock watering system comprises a housing, a basin supported by the housing (the basin being divided into an upper drinking portion and a lower reservoir portion), a flow control valve operably connected to a pressurized water source for maintaining a substantially constant level of water in the basin, a heating element adapted to selectively heat the water in the lower reservoir portion of the basin, and a temperature sensing assembly for sensing the temperature of the water in the basin. The temperature sensing assembly is operably connected to the heating element for selectively activating the heating element between one of an on mode and an off mode in response to the temperature of the water in the basin.