We report synthesis of reactive controller for a hot-water supply system in a medical institution for dialysis treatment using formal method and its real-time simulation based on measurement data in a practical hospital. Dialysis treatment requires heat to warm a large amount of water to the body temperature. Thus, synthesizing a controller guaranteeing the correctness of heat supply is of critical importance. The hot-water supply system considered in this paper includes heat generation equipments, hot-water storage tanks, and heat loads. We synthesize a reactive controller that reacts to changes of environment of the system affecting the supply such as failure and restarting of equipments, and achieves the continuous supply of heat to a critical load for dialysis treatment. Also, we experimentally demonstrate the synthesized controller with a real-time simulator that can interact with a dynamic analog environment. For this, a dynamic model of the hot-water supply system is developed through the measurement data. We then show that the synthesized reactive controller works effectively while reacting to the analog environment.