Pipe internal recirculation (PIR) is an undesired phenomenon which may lead to significant additional heat losses. Although different research institutes already measured singular PIR effects, there is still a lack of wide-ranging evaluations and practical solutions. This paper describes a test and evaluation method and reports on results regarding the influence of the pipe's slope, the material (copper, stainless steel) and diameter on the PIR caused heat loss coefficient. For combined pipe path arrangements a new method is presented, which allows to calculate the heat losses from basic investigations on horizontal and vertical pipe orientations. This method has been experimentally validated. Finally, the effectiveness of different measures for the reduction of PIR induced heat losses is presented.