To measure Silt Density Index (SDI), first rinse the pipe system for 10 minutes and ensure all connections are secure. After closing the inlet valve, connect the measuring device to a sample point and open external valves as needed. Rinse for one minute before attaching filter paper in place of a used filter; then set pressure at 0.21 MPa and drain water to time how long it takes to collect 100 ml, noting that results may vary significantly after letting water flow for an additional fifteen minutes.