The project, planned under the Operational Programme Competitiveness and Cohesion 2014-2020, will revitalise almost a third of the sections of the hot water network and 68.5 km of the network (from 227.3 km), with the aim of increasing the energy efficiency of the thermal system and the reliability of heat supply in the area of the City of Zagreb. More than half of the existing hot water heating system of the city of Zagreb was built during the period when the technology of sewage sludge was used, resulting in increased heat losses and increased heat disruptions. The current operation of the hot water network will revitalise the more modern technology free of pre-insulated pipes.