Every substation in a power grid system has its own sewerages to convey the storm water or rainwater into the environment. However, when the pumping station does not work on time, the water level may significantly rise causing the flooding of the electrical equipment and consequently its damage. Therefore, keeping track of the water level inside the sewerage system and controlling the pump on time can prevent unexpected errors in the power grids. This paper proposes an Internet of Things (IoT) based water level monitoring and controlling system to solve the issue. This research model is applied at 220kV Tra Noc substation, in Vietnam to prevent flooding in the rainy season on during the high tide days. The proposed system is a low cost in design and easy in maintenance. The system operates reliably and efficiently, serving as a basis solution for flooding prevention to substations experiencing similar flooding.