SANCHO is a time-dependent, deterministic model that simulates bacterial dynamics, free chlorine decay and biodegradable organic matter (BOM) consumption in water distribution systems. The software version of the SANCHO model is used in the drinking water industry to predict bacterial regrowth in pipes and to assist utilities in complying with drinking water regulations. The objective of this study was to determine the key parameters of the SANCHO model and thus identify the critical parameters of bacterial growth with respect to bacterial biomass (fixed, absorbed and free bacteria). Results indicate that five parameters have an undeniable influence on the regrowth of biomass in the distribution system as predicted by the model. These parameters are: bacterial mortality; maximum capacity for bacterial fixation; bacterial yield; initial concentration of direct substrates; and, maximum rate of uptake of direct substrates.