(1) The following equation and ARM 37.115.1314, Table 7 shall be used to calculate the saturation index: the saturation index equals pH plus temperature factor (TF) plus calcium factor (CF), plus alkalinity factor (AF) minus 12.1. (SI=(pH + TF + CF + AF) - 12.1.)

(2) If the total dissolved solids (TDS) are less than 1,000 ppm, 12.1 is used as the total dissolved solids factor. If the total dissolved solids are greater than 1,000 ppm, 12.2 is used as the total dissolved solids factor.

(3) Saturation index values shall be calculated weekly. Perfectly balanced water has a saturation index value of 0.0. A saturation index value below -0.5 shows corrosive water and a saturation index value higher than +0.5 shows scale forming water.

(4) The saturation index value should be maintained between -.5 and +.5. Ideal values are -.2 to +.2 on the saturation index.

(5) If the reading falls outside the range of -.5 and +.5 the licenseholder/operator shall initiate the saturation index adjustments to the pool water within 24 hours.