Saturation Index (sci) Question

[Andy D]

Does it matter if csi is -.5 or -.2 or 0.0 with a high CH of 550ppm I think it is better with a slight negative value to keep calcium from forming on pool surfaces, true or false? Pool math
States -.6 to +.6 is satisfactory.
TF-1000 test kit. Using Liq. Chlorine and pool math.
FC 12
TC 12
CC 0
TA. 80
CYA 80 to 90
PH 7.5
CH 550
Water temp 48F

15,000 gal in ground pebble tech pool
Triton 100HD 4.91sq. ft. filter area sand filter
Challenger High flow 2HP pump/motor

 

[JoyfulNoise]

It is preferable to keep your CSI between -0.3 and +0.3. Outside those limits there is the potential for corrosion or scale but no one can easily predict the rates.

Looking at your numbers, your pH is really too low for a winter pool. Why are you keeping it at 7.5? In the winter, you can easily allow your pH to drift up to 7.8 and it will probably stay there for quite a while. Right now, with a pH of 7.5, your CSI is -0.32. If you let it rise to 7.8, your CSI would be -0.04. You'll have fewer acid additions if you let your pH rise a little higher.