Calculation Methodology

Overview

All chemical dose calculations on this site use industry-standard formulas derived from published pool chemistry references. Doses are estimates based on product concentration and pool volume. Actual results may vary based on water temperature, cyanuric acid level, organic load, and other factors.

Chlorine Dosing

Chlorine doses are calculated using the relationship between product concentration, pool volume, and the ppm change required:

Where Product Factor represents the effective chlorine yield of the product per ounce per 10,000 gallons, derived from the product's available chlorine percentage and molecular weight.

Liquid chlorine (10% sodium hypochlorite) has a factor of approximately 7,500 oz × ppm per 10,000 gallons. Granular shock (65% calcium hypochlorite) and trichlor (90% available chlorine) use their respective concentration factors.

pH Adjustment

pH adjustment doses are based on the buffering capacity of the water (total alkalinity) and the magnitude of the pH change required. The formula accounts for the fact that water with higher alkalinity requires more pH increaser or reducer to shift the same pH amount.

pH increaser (sodium carbonate / soda ash) typically raises pH by 0.2 per oz per 10,000 gallons at standard alkalinity. pH reducer (muriatic acid or sodium bisulfate) lowers pH proportionally to acid strength.

Total Alkalinity

Sodium bicarbonate (baking soda) is the standard alkalinity increaser. The dose is calculated linearly: approximately 1.5 oz of sodium bicarbonate raises alkalinity by 10 ppm in 10,000 gallons. Muriatic acid can reduce alkalinity by aeration.

Pool & Spa Volume

Volume calculations use standard geometric formulas:

• Rectangle: Length × Width × Average Depth × 7.48 gal/ft³
• Circle/oval: π × (Diameter/2)² × Depth × 7.48
• Kidney: 0.45 × (A + B) × Length × Depth × 7.48
• L-shape: Two rectangles computed separately and added

Hot tub and spa volumes use the same formulas, scaled for typical dimensions.

Cyanuric Acid (CYA / Stabilizer)

CYA addition doses are calculated from the volume increase formula: cyanuric acid concentration increases linearly with product added, at approximately 13 oz per 10 ppm increase per 10,000 gallons. Reduction requires partial water replacement.

Saltwater Pool Salt

Salt addition doses are linear: approximately 8.3 lb of NaCl raises salinity by 1,000 ppm in 10,000 gallons. Salt cannot be chemically removed — dilution (partial drain and refill) is the only way to lower it.

Assumptions & Limitations

• Product concentrations are based on typical US retail formulations. Verify your product's label.
• Calculations assume well-mixed water. Allow sufficient pump run time after adding chemicals.
• Organic load, water temperature, and cyanuric acid level affect actual chlorine demand and are not modeled.
• Results are estimates. Always test before and after adjustments.