Bleach is also a corrosive. Corrodes pipes and eats the enamel off porcelains sinks. I have a septic and never use bleach in sink or laundry. I use Rid-X once a month down a different toilet each month and use non-bleach toilet cleaner. No solids down garbage disposal and thoroughly rinse dishes before placing in dishwasher. My septic guy said I have the cleanest tank he's ever seen, if you can believe that. Yuck... I have it pumped every 5 years. Good suggestions here and on Internet for proper care of septic systems. Good luck!