"L'eau c'est la vie" is a well known french expression for "Water is life", which reflects the fact that water is undoubtedly the most vital resource in the world. The main mission for water utility companies is to convey and distribute water that is of acceptable quality to satisfy the demand of the population at any time of the day. In the recent years, achieving this mission has become very challenging for these companies. Indeed, the rapid growth of the population and of the expansion of urbanization have significantly increased the demand for water on the one hand. While on the other hand, natural phenomenon such as drought as well as the impact of climate changes are making it almost impossible for water distribution companies to be able to convey the right amount of water where and when it is needed. The presence of water storage tanks in a water distribution network is aimed at alleviating this pressure by storing water and distributing it later in response of the variability of the demand across the network. The management of the tanks of the network is done based on the assignment of three level set-points which allows to meet the outflow demand of water from each tank, while maintaining the adequate flow rate of through the network. The set-points define the level at which the valves that enable inflow and outflow of water to the tank have to be switched on or off. However, operating the valves during different periods of the day in order to meet the water demand, may yield extremely high operational cost, since opening some of the of the valves will induce the running of pumps to maintain an adequate flow rate of water in the network. We present a network optimization model for managing the network of storage tanks in a water distribution system while minimizing the total cost of electricity involved. Computational experiments have been conducted to show that the proposed optimization model can be used to reduce the operational cost of managing the network of storage tanks for a water distribution system, while still being able to maintain the right amount of water in the tanks.