Pentair IC20 - Manual (Page 20)

12
IntelliChlor Electronic Chlorine Generator Installation and User’s Guide
Calculating the Saturation Index
The saturation index is a formula that relates pH, calcium and alkalinity in the pool water. A well balanced
pool water will have a formula result range between -0.3 and 0.3 Outside this range, the pool water is out of
balance, potentially damaging pool equipment or scaling the IECG.
The equation to calculate Si is:
Cyanuric acid in the form of cyanurate ions contribute to alkalinity. Thus, a correction must be made to total
alkalinity. We subtract 1/3 of the cyanuric acid level from the reading obtained in the total alkalinity test.
Total Alkalinity - 1/3 Cyanuric Acid = Corrected Alkalinity
This correction can be considerable in established pools with high cyanuric acid levels; for example, at 240
ppm cyanuric acid, the correction amounts to 80 ppm (240 ÷ 3 = 80).
Saturation Index Factors
SI = pH + CHF + AF + TF + TDSF
Saturation
Index pH as
tested Calcium
Hardness
Factor Alkalinity
Factor Tempera-
ture
Factor TDS
Factor