Here is a good explanation of how a system works via a man selling bacteria to enhance a septic system. Here is Mike Rowe doing this dirty business. When you open up a tank for inspection, this is what the pool should look like.
Most people never do that until the system is plugged and water or sewage backs up into the house. Some localities require a tank be pumped every three years because of smaller drain fields and/or slow air and water movement in the soils in the area. Most people don't do that either unless they are checked upon. The last thing we thing about is what happens when we flush the toilet until it doesn't work anymore.
Here is a point I had forgotten. "Homeowners and residents have a great effect on septic system performance. Using more water than the system was designed to handle can cause a failure. Also disposal of chemical or excess organic matter, such as that from a garbage disposal, can destroy a septic system. The following maintenance tips can help your system provide long-term, effective treatment of household waste." Too much organic matter in an anaerobic tank is going to cause failure."
I was taught a properly designed, used and maintained system never should need pumping. That is not reality. In reality we often overload a system and wonder why it fails later down the road. Do additives to a system work? There is research pro and con. The best results are obtained from a well designed system that is not overloaded but well maintained. They have the proper amount of tank size, input and output with the maximum amount of anaerobic digestion going on. Any improved results we get from an additive is a bonus and still not fail proof.
It always amazed me no one thinks what happens when you flush the toilet. We always leave that to somebody else. Teaching a family proper habits regarding a sewer system is no easy task. Someone has to do it though, so we all have a cleaner environment and avoid that dreaded announcement, "the sewer is backing up into the house!
Welcome to Septic 101, for my farm and farm loving friends around the world.