How does your plumbing system work? This picture and brief description will help you better understand your septic system.
Your septic system is in place of what many people would have in a city sewer situation. Instead of going to a main drain line in the street, it gets filtered into your yard.
So does that mean there is sewage in your yard? No. In fact, if you do have sewage in your yard that typically denotes a serious issue with your septic system. There are many different types of systems, but this is how most of them basically work.
Devereaux Van Dyne, Certified Professional Home Inspector