Saturation Index

Saturation Index (S.I.) = pH + TF + CH + TA - 12.3 If the Saturation Index (S.I.) is +0.3, the water is in balance. pH = actual pH reading. TF = actual °F temperature; use equivalent from below chart. CH = actual Calcium Hardness reading; use equivalent from chart. TA = actual Total Alkalinity reading; use equivalent from chart. Example: Find the Saturation Index (S.I.) based on the following readings: pH = 7.2; TF = 760; CH = 300 ppm; TA = 300 ppm S.I. = 7.2 + 0.6 + 2.1 + 2.5 - 12.3 S.I. = 12.4 - 12.3 = 0.1, the water is in balance. If the water is not in balance, using the chart below will assist in making adjustments.
Swimming Pool Temperature °F = TF		Calcium Hardness (CH) Expressed as PPM CaCO3 = CH		Total Alkalinity (TA) Expressed as PPM CaCO3 = TA
32	0.0	5	0.3	5	0.7
37	0.1	25	1.0	25	1.4
46	0.2	50	1.3	50	1.7
53	0.3	75	1.5	75	1.9
60	0.4	100	1.6	100	2.0
66	0.5	150	1.8	150	2.2
76	0.6	200	1.9	200	2.3
84	0.7	300	2.1	300	2.5
94	0.8	400	2.2	400	2.6
105	0.9	800	2.5	800	2.9