The top-heat-type heat transport loop previously proposed is a thermal device composed of a heated section, a cooled section, a reservoir, valves and pipes connecting these components. By utilizing the vapor pressure, the working fluid is circulated and the heat is transported downward from the heated section to the cooled section. In the present study, the liquid return line of the loop, which consists of vapor and liquid pipes between the heated section and the reservoir, was simplified to improve its airtightness, and its operation was confirmed experimentally. Moreover, based on the experimental results, the main factor to reduce the temperature difference between the heat sink and the reservoir is discussed.