We recently purchased a home with a septic tank that had not been pumped in nearly 20 years.  We had the tank pumped and found a tree root had grown into the tank near the intake pipe (between the pipe and the tank wall).  There was no damage to the tank and we removed the root.  

I am planning to remove the tree that caused the issue but also believe it wise to treat the leach field with copper sulfate as we have a couple of pine trees growing in close enough proximity to the leach field where their roots may be an issue.  I've seen recommendations from papers put out by various university extension offices that recommend a dosage of 2 lbs/300 gallons.  My question is this:  Where is the best place to apply the copper sulfate?  I can add it directly to the tank but believe it would get diluted and therefore be less effective.  Our tank doesn't appear to have a cleanout between the tank and the field.  I could add one and then administer the copper sulfate here but am unsure of the most appropriate way to do so.  We have a 1000 gallon tank.