Abstract: A system and method for dispensing microbial solution into a drain line. The system includes a disposable cartridge adapted to hold a quantity of microbial solution. The cartridge may be provided to the end user containing only a dry mix of microbes in a carrier medium. The end user may then remove a replaceable tab covering a fill hole, fill the cartridge with clean water, and replace the tab. The cartridge may then be inserted into a dispensing assembly, which includes an actuator that engages a nozzle on the cartridge at regular intervals. When the actuator engages the nozzle, a small amount of microbial solution is dispensed and routed through a tube to the drain line. The tube may attach to the drain line through a self-tapping valve assembly.