In this paper a mathematical model and a solution for the pump scheduling problem based on genetic algorithms is presented. The main objective is the reduction of the electricity costs of the water department for the pumping effort. The constraints are such as to maintain strategic security and reliability limits for each water reservoir. The reduction of the peaks during a scheduling period is equivalent to the minimization of the electricity costs and this is in fact used in the solution process of our experiment. Actual results with the pump scheduling results of Chania, Greece are also presented