Optimal Maintenance Time for Water Distribution Systems Considering Deterioration Rate and Maintenance Costs

Stable operation of water distribution systems requires an appropriate maintenance time that considers both pipe deterioration rate and maintenance costs. In this study, a preventive maintenance model was applied to an actual water distribution system to determine the optimal maintenance time for individual water distribution pipes. The deterioration rate of water distribution pipes was evaluated considering uncertainty in corrosion using Monte Carlo simulation. The maintenance model was established based on condition-based maintenance, in which preventive or corrective maintenance is performed according to the deterioration rate relative to the usage and failure limits. The probabilities of preventive and corrective maintenance were estimated from the deterioration rate distribution and combined with the corresponding maintenance costs to calculate the CR. The CR was evaluated for different maintenance times, and the time at which it began to converge to a relatively constant level was determined as the optimal maintenance time. The results showed that the optimal maintenance time generally occurred before the deterioration rate reached the serviceability limit. After the CR began to converge, delaying maintenance resulted in little additional cost reduction, whereas the deterioration rate continued to increase. These results indicate that considering both the deterioration rate and maintenance costs can provide an economically appropriate maintenance time before the serviceability limit is reached. Therefore, the preventive maintenance model applied in this study can be used to determine the maintenance time for individual pipes, establish maintenance priorities, and support preventive maintenance planning for water distribution systems.