Today waste management has entered a new stage. Since wastes still contain natural materials and energy that can be extracted, it should be treated in effective ways, for example, for energy recovery or material recycling. Many countries and the municipalities have therefore made waste treatment strategies in accordance with for example, EU directives or governmental regulations. In such circumstances, Envac is one of waste management companies in Sweden, which collects different kinds of waste fractions through an underground pipe system by means of air pressure. In Hammarby sjöstad in Stockholm, currently organic waste, combustible waste, and newspapers are collected by the Envac’s system, however a cross contamination between organic fraction and newspapers has been observed. We therefore performed on-site waste transporting experiments in order to solve this cross contamination and suggest an optimum transporting condition which means that waste bags can be transported with high rate and acceptable condition to the terminal. From the previous study, bag quality and transporting speed were supposed to be the factors that affect the waste purity. Then on-site experiments were designed and carried out based on these factors. In the end, we proposed the optimum condition depending on the bag quality and clarified the causes of the cross contamination.