I have Wet Edge Luna Quartz plaster and my pool is about a year old. The pH has only recently stabilized and the sweet spot for my pH seems to be around 7.8. I still need to add some MA about once a week or so (which is way down from the amount and frequency of just a couple of months ago), and the pH will slowly rise to 7.8 and level off for several days.
My test results are as follows:
At 75 degrees CSI is -.12 which ought to be fine. But if I tried to keep pH at say 7.5 CSI goes down to -.34 (and at 7.2 is -.58) which could be problematic. Of course, I would like a lower CH but my fill water is 150 and with the continued drought it's hard to get it lower. Further, a partial drain and refill now would be illegal because of mandatory water rationing. If if wanted to keep my pH down to 7.5 it would require adding about 2-3 cups of MA every third day because my pH will rise until it reaches 7.8.
So my question is why does Wet Edge recommend pH of 7.2-7.6 without regard to CSI? Should I care at all if I keep my CSI slightly negative and not let pH go over 8.0? Heck, even at pH 8.0 CSI is -.02 which ought to be fine.