What is the minimum amount of bleach I can use to disinfect laundry? I’m mostly interested in killing mildew on towels and generally find that a very small amount will do. What does science say? I have a septic system and so I don’t want to use the 3/4 cup per load that is standard.
Simple answer to your question; the recommended amount of Clorox Regular-Bleach, 3/4 cup for regular loads or 1¼ cup for large/heavily soiled loads, should do the job. Clorox Regular Bleach2 is the best solution as a registered EPA disinfectant.
As for the septic tank, you shouldn’t worry about using the recommended amount of bleach. The active ingredient, sodium hypochlorite, is extremely reactive and nearly all is consumed in the wash and reverts to mostly salt and water. The small amount that may be un-reacted will encounter lots of organic soil in the drain pipes and be consumed long before it reaches the septic tank.