The reliability of heat supply in cities is largely determined by the actual condition of pipelines, for example, corrosive and erosive wear. Comparative analysis of methodological approaches to assessing the technical condition of district heating networks shows that the most innovative and effective approach is internal pipe inspection using non-destructive magnetic testing. The article presents the results of research tests of the method in the context of its use for maintenance and retrofitting of the heating infrastructure in Yekaterinburg, a Russian city with a complex topology of utility networks and extremely uneven tear and wear on some sections of the networks. The authors describe the technical and economic peculiarities of using internal pipe inspection methods at various stages of testing and formulate qualitative and quantitative criteria for assessing the effectiveness of the method being presented. Recommendations have been suggested for the optimum application of the method by heat network operators, especially those operating and servicing district heating systems.