If you are selling your house in Washtenaw County then you will be required to have your Septic System Must Pass Inspection to recieve a
"Point of Sale Approval"

If you want to learn more about Septic Systems
then here are some links that you might find interesting

Washtenaw County Inspection At the Time of Property Transfer.
Onsite Water & Septic Disposal System

Shock Clorination & Control of Iron Bacteria

All Septic System Website

Septic tank Maintenance Suggestions

How Sewer  & Septic Systems Work