Although CSOs are expensive infrastructures, which are important to reduce pollution from urban areas during wet weather, they are often not operated effectively. Despite of technical difficulties, major problems in CSO monitoring and performance assessment are caused by non-technical bottlenecks. Through a policy analysis we identified organisational and political problems as the biggest obstacles to the effective operation of CSOs. In addition, we investigated effective measures or incentives to overcome organisational and political obstacles. Our results suggest that a surprisingly high 84% of the CSOs operated by Swiss wastewater associations are monitored. In most cases the information is used to improve operation, but not for better planning or for regulatory performance assessment. The most desirable instrument seem to be legislative performance targets, which is preferred by both wastewater associations and cantonal stakeholders. From a political point of view, the cantonal authorities also consider a transfer of competences from the municipalities to the wastewater associations to be effective, i.e. wastewater associations should operate CSOs instead of municipalities. In contrast, Swiss associations prefer financial incentives, such as a one-off subsidy for the installation of CSO monitoring equipment. Before implementing certain instruments, and in particular regulatory instruments, we highly recommend to assess their impact on overall policy processes and individual stakeholders. In the long term, only the implementation of a carefully balanced, uniform strategy can overcome organizational and political barriers and thus can lead to effective success in water protection.