170 Amount Conversions Ounces to Pounds Ounces ÷ 16 = Pounds Fluid Ounces to Gallons Fluid Ounces ÷ 128 = Gallons Distance Conversions Yards to Feet Yards x 3 = Feet Meters to Feet Meters x 3.28 = Feet Surface Areas Rectangle/Square Length x Width = Square Feet Circle (Radius = Diameter ÷ 2) 3.14 x Radius x Radius = Square Feet Pool Volume (Average Depth = Shallow + Deep ÷ 2) Rectangle/Square Length x Width x Average Depth x 7.5 = Gallons Circle 3.14 x Radius x Radius x Average Depth x 7.5 = Gallons Turnover Rate Pool Volume ÷ Flow Rate ÷ 60 = Hours Flow Rate Pool Volume ÷ Turnover Rate (hours) ÷ 60 = Gallons per Minute Filter Surface Area Flow Rate ÷ Filtering Rate (Filter Specific) = Square Feet Heaters - BTU Volume x 8.33 x Temperature Rise = BTU Bather Load/Pool Capacity ** See State Public Swimming Pool Code Book Calculation Formulas Saturation Index The Saturation Index (SI) is a method of determining whether water will deposit calcium carbonate or maintain it in solution. In short it tells you whether your water is corrosive or scale forming. The SI incorporates the five balance factors: pH, total alkalinity, calcium hardness, temperature, and total dissolved solids. For pool and spa water, the ideal result of performing this index is to have a result of zero, i.e., SI = O. Balanced water is between - 0.3 and + 0.3. Corrosive water is - 0.4 and lower. Scaling water is + 0.4 and higher. Having water outside of the balanced range can contribute to extensive damage to the pool surface, equipment and structure. Calculating the Saturation Index To determine whether pool or spa water is properly balanced, a full water chemistry analysis is necessary. When calculating the SI use the factors below. If an actual measurement is not found in the chart, use the next greatest value. The measured pH value is used directly in the formula. There are many slide rule saturation index calculators available that make it quick and easy to determine your Saturation Index. Value Factor pH Temperature Calcium Hardness Alkalinity Sub-Total Total Dissolved Solids (TDS) Saturation Index **High levels of Cyanuric Acid can contribute to false Saturation Index readings. Cyanuric acid should never be above 30 ppm due to the adverse effects on sanitizer activity. * Free with any consultation SI pH Tf Cf Af TDSf Saturation Index pH as tested Temperature factor Calcium factor Alkalinity factor TDS factor = + + + _ Temperature Calcium Hardness expressed as CaC03 Total Carbonate Alkalinity °F °C Tf ppm (mg/L) Cf ppm (mg/L) Af 32 0.0 0.0 25 1.0 25 1.4 37 2.8 0.1 50 1.3 50 1.7 46 7.8 0.2 75 1.5 75 1.9 53 11.7 0.3 100 1.6 100 2.0 60 15.6 0.4 125 1.7 125 2.1 66 18.9 0.5 150 1.8 150 2.2 76 24.4 0.6 200 1.9 200 2.3 84 28.9 0.7 250 2.0 250 2.4 94 34.4 0.8 300 2.1 300 2.5 105 40.6 0.9 400 2.2 400 2.6 800 2.5 800 2.9 Saturation Index Factors Total Dissolved Solids Factor Less than 1,000 ppm (mg/L) 12.1 1,000 ppm (mg/L) or greater 12.2
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