Seepage of good quality water into the sewer pipes results from the degradation and neglect of maintenance of this thirty-year-old sewer network. Rehabilitation of such an infrastructure is costly, and the replacement option seems to reach its sustainable limits when addressing future peri-urban development. At the same time the limited flow capacity of the old sewer network also increases the number of CSOs. Thus, best management practices need to be proposed and integrated in the urban planning (see Chapter 4).