The first vortex solids separator facility in Germany for CSO control was installed in 1987. Solids separation efficiency was optimized in the hydraulic laboratory using scaled down models and artificial tracers to simulate typical sewage particulates. The facility comprises two parallel operating vortex separators servicing an impervious area of 11 ha with a population of 1,500 people. The specific storage of the facility including the separator volume and in-line pipe storage is 7.2 m3/ha, about 1/4 - 1/2 of that required per German standards. A multi-year evaluation program was conducted. The first phase noted operational reliability, hydraulic loads and overflow frequencies. In the second phase pollutant removal efficiencies were monitored. The results were favourable indicating that the separator is now ready for use.