The heat storage tank is an important element in any heating system where the heat source is not able to provide heat accordingly to consumer demand (for example solar collector systems, solid fuel boilers etc). Better heat storage efficiency can be achieved by providing good thermal stratification in the heat storage tanks. One of the best methods of increasing the degree of thermal stratification is the stratification pipes. In the Environmental monitoring laboratory of the Institute of Energy Systems and Environment (Riga Technical University, an experimental heat storage system has been developed and used for testing and studying stratification devices under different thermodynamic and hydraulic conditions. The experimental study carried out on the efficiency of the stratification pipe produced by German company SOLVIS Solar Systeme GmbH under different flow parameters, has been analyzed. The main aim of the experimental study was to define optimal heating system operation parameters to achieve good performance of the stratification pipe and a high degree of thermal stratification in the heat storage tank.