I've touched on this issue a few times, but I don't think I've ever had this specific question. Here's my issue.
I've had rising pH since my pool was built 19 months ago, although it's slowly getting better. I have a spill over spa (although the water doesn't have far to fall--the top of my spa is even with the normal water level), a SWG and an oversized pump. My pH tends to reach around the 8.0 range and seems to top off before it gets to 8.2. I don't believe I've ever had a dark purple test result to match the 8.2 color sample in my test kit. I just get various shades of dark red. I usually add enough MA to lower the pH to 7.2 or 7.5 and then it goes back up over 4-5 days.
I tested my water yesterday evening after several days without adding MA and the pH was dark red. I figured it was around 8.0 so I added 48 oz. of MA and after an hour retested and the pH was right at 7.2. Using the pool calculator to back into my pH before the addition my pre-MA addition pH was at 7.9. So my 8.0 estimate was fairly close.
The pool calculator said my CSI was -.59 with 80 degree water after the MA addition. Note that 80 degrees is very unusual for SE Texas this time of year. We've had several days of overcast/rain. My temp would normally be around 89 which would lower the CSI to -.51.
Here are my full test results:
pH 7.9 (after MA 7.2)
TA 60 (usually fluctuates between 60-80)
Before the MA addition the pool calculator says my CSI was -.14 at 80 degrees (but it would have been -.06 at my normal 89 degrees). Even if my pH was 8.0 at my normal 89 temp the CSI would have been negative at -.04. So my question is whether I should care so much if my pH gets to 8.0 or even 8.1 so long as I keep my TA low giving me a near zero CSI? Oddly, plugging in 8.2 for pH at my levels shows a CSI of -.16. That doesn't seem right. In any event, should I be concerned with pH at near 8.0 levels so long as my CSI stays near zero?