This paper describes a project that investigates confined stormwater infiltration/filtration systems and their ability to reduce and retain pollutants present within stormwater runoff. These highly innovative Water Sensitive Urban Design (WSUD) systems are located in three locations to the north and south of Sydney, Australia. They are positioned at different geographic locations and face different subsoil conditions, pollutant loadings and other constraints. The systems contain specially designed porous concrete pipes. Stormwater exfiltrates through the permeable walls of the pipe into the surrounding substrate media material. This provides primary, secondary and tertiary treatment of the stormwater. The systems are positioned underground and are designed to ensure that the integrity of surrounding soil, vegetation, groundwater and receiving water is not negatively impacted. The focus of this paper is the results obtained from the analysis of stormwater samples collected from the inlet and outlet of the systems. The results indicate significant reductions in the concentration of pollutants present in the stormwater that passes through the system. Some of the findings include: approximately 45% reduction in nutrient concentrations, while zinc concentrations have been lowered by approximately 90% and Faecal Coliform levels have been reduced by approximately 95%. The monitoring work is ongoing and further sample collections are required to further validate the findings.