Is there a way that I can measure the health of my septic system? The
toilet has started to gurgle when flushed. I have heard that this can be
an indicator of a bad system.
Can a truck or tractor driving over the tile bed (not the tank itself)
cause damage? How about a tree falling hard onto the ground above the
tile bed?
I also heard that there is a bacteria or enzyme additive that I can pour
into the system. Is this additive any good?
As a side note, the tank has been pumped within the last year or two.

Thanks for your input.

Just an FYI:

The Septic System Owner's Manual
By Lloyd Kahn, Blair Allen, & Julie Jones

http://www.shelterpub.com/_shelter/ssom_book.html

or he

http://www.amazon.com/Septic-System-.../dp/093607020X