I reduced my TA down to ~50ppm to compensate for a drifting pH. The only issue I have is my CSI seems extremely off now, appr. -0.30 to -0.40 depending on pH and water temp. Here are my number right now:
FC = 7
pH = 7.8
TA = 50
CH = 280
CYA = 40
Borates = 50
CSI = -0.26
Temp 75F
If my pH drifts to 8.0, which it still does but now it takes longer, then if I lower pH to 7.6, CSI is -0.39. Those values should soon be offset a little (0.05 to 1.0 for 80 and 85F water, respectively) when the temp rises today and tomorrow now that the rain and cold have moved out of Northern Cal
Are these CSI values harmful to the pool? I do have some scaling on the tiles, but that was there last June 1 when we bought the home. The chemistry was probably out of wack for sometime, and it was a foreclosure. They were using hockey pucks when I bought it, and I quickly switched to BBB. Only issue has been pH drift.
FC = 7
pH = 7.8
TA = 50
CH = 280
CYA = 40
Borates = 50
CSI = -0.26
Temp 75F
If my pH drifts to 8.0, which it still does but now it takes longer, then if I lower pH to 7.6, CSI is -0.39. Those values should soon be offset a little (0.05 to 1.0 for 80 and 85F water, respectively) when the temp rises today and tomorrow now that the rain and cold have moved out of Northern Cal

Are these CSI values harmful to the pool? I do have some scaling on the tiles, but that was there last June 1 when we bought the home. The chemistry was probably out of wack for sometime, and it was a foreclosure. They were using hockey pucks when I bought it, and I quickly switched to BBB. Only issue has been pH drift.