Abstract: A livestock watering device includes a liquid supply tank having an access opening in its top and an outlet opening in its lower end. A removable lid hermetically closes the access opening and an automatic feed means transfers liquid through the outlet opening to a collecting vessel arranged therebeneath in response to liquid consumption from the vessel. An electric heating element is attached to the lid and extends into the tank and is immersed in the liquid therein. The heating element comprises a resistance heating foil inserted between two concentric tubes sealably connected together to electrically isolate the foil from the liquid in the tank. The tubes define a tubular structure having a first open end removably secured to the lid and a second open end spaced above the bottom of the tank whereby the liquid in the tank is heated by contact with the inner and outer surfaces of the tubular structure.