Among the most complex activities in water companies is extracting accurate operational data of Urban Water Infrastructure (UWI). Hence, the use of data-based methods would be faced limitations for asset management of the UWI. This shortcoming could be improved using knowledge-based decisions. In this study, using this method, Maintenance-Rehabilitation Planning (MRP) of urban water pipes is assessed. Hence, the criteria effective on the MRP of the pipes were firstly determined. Then, two groups of experts in Iran and Brazil were invited to rank the determined criteria. For this purpose, a Multi-Criteria Group Decision-Making (MCGDM) method was developed based on the nominal group technique. This MCGDM method was implemented based on two approaches; first, the viewpoints of non-weighted decision-makers were considered; and second, the experts were weighted to rank the criteria. Finally, the results of these approaches in the two countries were pairwise compared. This comparison led to improving the literature and management in water companies of Iran and Brazil by identifying the effective criteria for the MRP of the pipes based on knowledge-based decisions. Further in this field, it was found that weighting the experts have no decisive effect on the results; and this is only effective in groups where the decision-makers weights are identically distributed. Moreover, it was found that there is a relation between the similarity of results and the similarity of experts’ profiles in knowledge-based decision groups of various countries such as Iran and Brazil.