Soft drinks and other caloric beverages are supposed to be involved in the development of overweight and obesity in children. The intervention strategy of our study was to promote water consumption by facilitating access to tap water in schools assuming a concomitant decrease in caloric soft drinks at least at school. The environmental modification of installing a water dispenser at school and delivering a special bottle to each child in the intervention schools was supported by a few educational lessons. These lessons were held by the class teachers who received a prepared 6-hour curriculum dealing with the importance of water for the body and of water intake. For the study 17 randomly selected schools were assigned to the intervention group, 15 schools to the control group that did not receive any intervention. Body weight and height to calculate BMI as primary outcome were assessed at baseline and after the intervention period of 1 school year. As secondary outcome drinking and physical activity habits were evaluated at baseline and after the intervention. The water flow of the dispenser was measured at regular intervals. In addition, data of process evaluation was collected to measure acceptance and feasibility of the intervention in the school setting.