Unlike a performance inspection, which is tipically done during a somewhat impractical time (realestate transaction), a maintenance assessment is typically done for a homeowner who has a genuine concern for how their system is functioning and is curious if there is anything that can be done to help it keep working for as long as possible.
A proactive home owner might also do a maintenance assessment when preparing for their sale. It's prudent to find out how the system is functioning and to take care of any restoration that might be needed ahead of time. The farther ahead of time the better.
Locating components using various inspection & locating equipment
Using a pipe camera to assess the transport pipes from the home to the tank and downstream
Using a tank camera to assess the tank for signs of misuse, leakage, back up or misaligned components
Hand excavating to expose individual buried components such as a distribution box or dispersal pipes
Using a pipe camera to assess the pipes in the dispersal field to evaluate their condition, performance, and location
Hand digging in spot locations to evaluate the soils in the dispersal area
Pumps & controls
Treatment plants or other treatment methods
Indexing or other valves
Effluent, disc or other filters
Regardless of the type of system & regulations of its day, the goal of the inspection is generally the same: to locate & assess how the system is performing based on the intention of its design.