It is well known that the use of certain surfactants and counterions can cause drag reduction in pipe flow. This phenomenon can be applied to a district heating and cooling system. In such a system, however, heat transfer reduction correspondingly occurs as drag reduction does. This should be a major problem as far as heat transfer application is concerned. In our study in this regard, we focused on drag reduction in practical heat exchanger tubes and determined the effect of drag reduction caused by a surfactant solution of Ethoquad O/12, We used three rough tubes with different groove pitches and heights in our experiments to evaluate the effect of the roughness shape, From the results, we estimated the magnitude of the heat transfer reduction.