Abstract: A water heater, converted from existing water heaters or in newly designed and manufactured water heaters, having a condenser tube of a refrigeration unit in thermal conductive contact but not intimate contact with the water to be heated, and having a sheath tube in conjunction with and outwardly disposed to the said condenser tube, and having the inter-space or inter-spaces between the said condenser tube and the said sheath tube filled with thermal conductive material, said inter-space being open or fragilely rupturable to the outside of the water heater.