Storm water filters are being used in a number of projects with rain water installation. The builders in Kochi are now specific about the use of rain water harvesting systems in their projects to reduce the demand for water.

Capture volume of the filter is determined by the local requirements or are sized to treat 85% of the annual runoff volume. The filter bed is sized in such a way that it can discharge the capture volume over a period of 48 hours. Above the underdrain system the filter bed extends about 18 inches thick. To reduce the resuspension of the accumulated sediment energy dissipation is included in the inlet design. To facilitate access to the sedimentation and filter basins for maintenance activities a maintenance ramp is included in the design. There are designs that make use of covered sedimentation and filtration basins. These structures should be accessible to vector control personnel through access doors to help vector surveillance and controlling the basins if required. Before installing the media the tributary area should be completely stabilized to avoid premature clogging.

The performance of media filters in terms of the pollutant removal is generally characterized by the percent reduction in the influent flow. Hence there is a relationship between the influent and effluent concentrations. Hence if a device achieves a 75% reduction, it has an effluent concentration of 25% of the influent concentration. Studies comparing the influent and effluent concentrations show that the effluent concentration is relatively constant and independent of influent concentration. Hence the effluent concentration characterizes the performance more accurately.