In recent times, research and applications on district heating systems are moving into a new challenging direction which aims at realizing an innovative and more efficient generation of systems. Among the novelties that are being integrated within district heating networks, special mention goes to the reduction of supply temperatures. This will also encourage the integration of low-grade and sustainable energy sources and the reduction of primary energy consumption. However, various elements of criticalities exist in reducing supply temperatures within existing district heating infrastructures. These issues are partially counterbalanced by multiple factors, including the oversizing of some existing networks, the opportunities of building retrofitting, and the possible actions that can be applied to overcome potential constraints. In this framework, this work analyses how potential actions that can be implemented at the substation enable temperature reduction in existing networks that have been designed for operating with high supply temperature. The analysis is performed on a real test case in order to present the actual room for improvement taking into account the possible issues on data quality/availability. Results show that relevant reductions can be achieved by an appropriate management of the transition.