Physical, chemical and biological actions can cause defects in urban infrastructure including drainage culverts. Defects in the urban infrastructure, in turn, have significant social and economic impacts. To reduce the adverse effects, developing methods for mitigating defects in drainage culverts is essential. To the best of the authors’ knowledge, there is no system to support the inspection and diagnosis of defects in reinforced concrete drainage culverts. This paper presents a classification system for the inspection, diagnosis and rectification of defects in reinforced concrete (RC) drainage culverts. Based on numerous documents analysis, the main defects in drainage culverts are identified and classified. All the direct and indirect possible causes of the potential defects, as well as the repair techniques, are explored, and classification systems are developed. The proposed innovative RC drainage culverts inspection system intends to help inspectors to standardise their procedures, detect defects, propose possible causes of defects and understand the mitigation strategies.