SUMMARY
At present times, in the context of rising fuel and energy prices the energy saving is very actual phenomenon. A better building insulation and the replacement of large transparent constructions will significantly reduce heat loss of the building. The hydraulic adjustment of heating systems is also a essential requirement for optimum operation of buildings. The peak load of the heating system occurs only a few days a year, mostly the transitional period dominates. Correct settings of control valves and pumps can achieve significant savings from the energy requirement of the building. This study is focused on the hydraulic analysis of rising pipes in reference high-rise building in Bratislava. The main aim of this study was to determine hydraulic behavior of two reference risers and to analyze wall roughness of the old seamless steel pipes and buoyancy effect on hydraulic conditions.