On Mon, 31 Jan 2011 18:43:56 -0500, "Colbyt"
wrote Re How Much Rock Salt to
Kill Roots?:

What is the prescribed dosage of rock salt to control roots in a
drain?

I don't know what a "prescribed" dosage would be, but I myself pour
about 30 gallons of a saturated water salt solution into my leach
field (down line from the septic tank) once a year. I came up with
this amount from doing research on various sources.
--
Work is the curse of the drinking class.