I would test 191 on a small inhouse basis to see if it meets your need, as yes its costly. If any irrigation needed I would not trust the restriction guide,if you irrigate do not use would be my policy.I have the same policy on Sonar as it is difficult to get it to test to safe levels,you then also have to consider landscape plants for which tests probably have not been done.Ill see if Sue at Vertex has a file she can post on the testing and lift data for their systems for an example. I have the test results on our site under "A word about diffusers" Ill see if she will do a sample of a 4 acre lake with a 6 ft average depth and a desired turn of twice per day (for information purposes) not trying to advertise . If the moderators would rather this be PM'd to you we can do that too.
