One instance in which the addition of bacterial additives might be helpful would be when there are significant amounts of medications entering the septic system through human waste. This would be rare, such as you might find with septic systems where one or more resident of the home is on a number of prescription medications or undergoing a chemotherapy regimen. (Never flush unused medications down the toilet. Unused pills and medications should not be disposed of in this way.) Contact your local county health department about programs to collect and dispose of unused medications. There may also be the rare instance when poor soil condition in your drain field might benefit from the addition of bacteria.