In order to maintain water quality in water distribution systems, disinfection is performed by chemical addition. Chlorine, the most commonly used disinfectant, decays over time by reaction with organic materials in the water and produces potential harmful disinfection by- products (DBPs). Therefore, it is important to maintain the free chlorine residuals throughout the system within specified limits. Here, optimal valve operation has been combined with booster disinfection for water quality improvement. Valves are operated to alter the flow distribution in the network, prevent isolation of disinfectant and direct disinfectant laden-water to locations where it is required. A real-time optimal valve operation and booster disinfection problem is formulated as a single objective optimization approach. The objective is to minimize chlorine injection while maintaining chlorine concentrations and pressures at consumer nodes. The problem is solved using a single objective genetic algorithm. This paper presents the problem formulation methodology and its uniqueness.