David Martel wrote:
Joe,

Roots in the septic tank? Is your septic tank cracked and leaking? This
is not a good thing. Find out and fix the problem before your well gets
contaminated.

Not likely, it's almost certain simply a lid not completely
tight--roots can find and work their way through the smallest of
cracks.

The easiest solution assuming there isn't a major problem (and the
septic service guys should have determined that--if not, then you do
need to find out where they are actually coming from) is the copper
sulfate around the tank. I had similar problem and solved it by
burying a piece of 3/4" plastic pipe w/ a small hole drilled every 6'
or so about a foot deep around the perimeter of the tank where the
roots were coming from. Put a T in the middle and left a piece coming
up just above the surface and capped. Filled the pipe w/ the
crystals--figure it will take several years for the supply to leach out
totally but will hopefully be able to refill it from the opening w/o
digging it up to do so.

I'd avoid the in-the-tank root treatments if at all possible although I
suspect a one-time treatment now after it has been cleaned would not be
fatal.