Rainfall-dependent infiltration and inflow into sanitary sewer collection systems is an ongoing concern for many municipalities; the addition of the RDII component to normal dry weather flow can overload system capacity and result in pipe surcharging, sanitary sewer overflows, water in basements, and other problems. Computer modeling of the existing sanitary sewer system can provide insight into the nature of the RDII problem and help direct efforts to combat it. The US EPA SWMM5 program has a flexible RTK unit hydrograph routine for modeling RDII entry to collection systems, consisting of sets of three triangular unit hydrograph, along with initial abstraction parameters. Determining these parameters (R1, R2, R3, T1, T2, T3, K1, K2, K3 can be a complex, time consuming and thus expensive effort. This presentation describes a streamlined approach to quickly determining and calibrating these parameters from existing monitoring data using sensitivity-based, radio tuning.