Sooooooo, you'd rather have a clogged up sewer, than a dead plant eh? Is
that what you're getting at?
re: (salt) kills the roots but leaves the trees unharmed
Curious...how does this work? How does the salt know where to top
doing it's damage?
According to the document at this site:
Salt-weakened plants are more susceptible to insects, pathogens, and
the environmental stresses of drought, wind and ice. Damage can occur
to plants located up to 50 feet away from a heavily salted area. You
may not even see the damage until the following June or later when
brown leaf margins suddenly appear as a tree endures its first stress
of the season. Salt damages plants in two ways - via an airborne spray
that kills dormant buds by penetrating leaf scars, and in the soil
where it breaks down into its two components - sodium and chlorine -
which act differently to kill the plant.
I had almost the exact same thing happen a couple months back. Septic
was pumped 6 months prior, but it acted like the system was full. It
would dain slowly, seemed fine for the first couple showers in the
morning then would be slow. I tried several different chemicals and
tried snaking through every opening I could get to. Only one I
couldn't snake was the main cleanout, only because it wouldn't open.
Ended up having a plumper with a pressure sprayer come out. He was
able to get the main clean out open and ran the pressure spray out the
main line to the tank. Things are perfect now, but I had a day of
hell trying to clear it myself. You trouble sounds exactly like what
I had. Oil and grease build up on the out flow pipe. Good luck.