Yeah the GFO change was the only thing I changed that day so I assumed that was the cause for the dip. I wanted to understand the chemistry behind it.

I have a PH statement at the end of my Alk Dose program but like you said too many things effect PH for me to use PH as my only dose trigger. I know PH is a little more critical when using a Calcium reactor.

If PH < 7.9 Then OFF