The growing number of challenges in how to manage aging infrastructures, while maintaining a suitable level of service, have become major problems for many municipal water utility companies. As a result, municipalities are increasingly considering the concept of risk assessment and prioritization as the first and an important step that has to be used towards effective asset-management practices. Most experts agree that the main effort has to focus on implementing risk-based asset-management practices meeting a degree of sustainability decision-making process. However, there are so many challenges to establish common practices and understand the ground for operational implementations of the concept of the risk. This paper aims to form a basic decision support model to address urgent needs of risk-based water main asset-management tools. Furthermore, efforts have been made to demonstrate how this model can be used to support decision-makers to reach sound decisions for prioritization of mitigation with more informed and sound collective judgments of peer experts. This includes addressing the existing or potential risks based on scenarios, likelihood, consequences of the outcomes, and results of the action. In conclusion, this model would benefit decision-makers in evaluating further different planning horizons and set priorities for replacement or rehabilitation maintenance programs.