Analysis, design, and maintenance of isolation valves in water distribution networks: State of the art review, insights from field experiences and future directions

: Isolation valves play a primary role in water distribution networks as their operation enables isolating the part of the network undergoing planned or extraordinary maintenance, in the context of rehabilitation or pipe break repairs, respectively. This paper presents a review of the current state of the art of isolation valves, with a focus on the problems of analysis, e.g., assessment of the performance of the network in segment isolation scenarios, design of optimal valve locations, and selection criteria/methods for identification of the valves to maintain. After describing and classifying the main scientific contributions, the paper proceeds by reporting the results of a survey to water utility staff in the United States, Italy, Portugal, and Iran, aimed at analysing the current practices adopted for the positioning and maintenance of isolation valves in real case studies. The paper ends with a discussion on the analysis of scientific literature and results of on-field surveys, highlighting critical points for potential future developments, including the connection between the design and maintenance of isolation valves, the trade-off between increasing validity and reducing complexity of reliability assessment methods, and more precise modeling of isolation valves systems.