This video is from Canada, but it’s basically the same system as far as how it functions. As you can see, bacteria plays a major role in the operation of your septic system. For this reason you want to avoid putting chemicals or bleach down your drains. The bacteria can not survive contact with these materials and if you kill the hardworking bacteria the system will no longer function.
A great video by “This Old House” TV show further illustrates how your septic system works and what happens if you put the wrong things into the system.
More info on what is safe to put down the drain.
Kevin Hicks 