It is well established that water quality deteriorates in distribution systems. Two major water quality issues are the loss of disinfectants and the growth of bacteria. Since utilities are charged with protecting public health, they must limit biological activity in drinking water through maintaining an effective disinfectant to the consumer's tap. To achieve effective disinfection, the disinfectant rate must exceed the bacterial growth rate. This research proposes a simple method to establish effective disinfection by using a "stability point" equation that compares the disinfection rate to the bacterial growth rate by applying fundamental biological modeling concepts and parameters derived from batch tests. Includes 24 references, figures.