The effects of pollutants in runoff on the environment have forced the development of several water treatment systems with the aim of reducing this kind of pollution before its final discharge. Nevertheless, many of these systems do not behave satisfactorily and, additionally, there is a low level of confidence in the treatment performance. This paper introduces the results of research on the long-term performance of a laboratory prototype of a system for catchment, pretreatment, and treatment (SCPT) designed to deal with the polluted runoff water. Solid and oil treatment efficiency were the focus of the study. After 14 consecutive simulated rain events, the treatment efficiency levels achieved by the prototype are higher than 80% of solids and 90% of oils.