Chemical dosage calculations for swimming pools

Chemical dosage calculation is an important aspect of maintaining proper water balance in a swimming pool. The chemical dosages required will depend on the specific chemical being used, the volume of the pool, and the desired levels of the various chemical parameters. Here are some common formulas for calculating chemical dosages in a swimming pool:

1. Chlorine Dosage: Chlorine is commonly used as a disinfectant in swimming pools. The recommended free chlorine level in a pool ranges from 1.0 to 3.0 parts per million (ppm). To calculate the amount of chlorine needed to achieve a specific free chlorine level in a pool, use the following formula:

Chlorine Dosage (in pounds) = Pool Volume (in gallons) x Desired Free Chlorine Level (in ppm) ÷ 10,000

For example, if you have a rectangular pool that is 20 feet long, 10 feet wide, and 5 feet deep (with a volume of 7,480 gallons) and you want to achieve a free chlorine level of 2.0 ppm, the chlorine dosage required would be:

Chlorine Dosage = 7,480 x 2.0 ÷ 10,000 = 1.49 pounds of chlorine

2. pH Adjustment Dosage: The pH level of a pool should be maintained between 7.2 and 7.8 for optimal swimmer comfort and chemical effectiveness. To adjust the pH level of a pool, use the following formula:

pH Adjustment Dosage (in pounds) = Pool Volume (in gallons) x (Change in pH Desired ÷ 0.2)

For example, if you have a circular pool with a volume of 19.63 cubic meters and you want to increase the pH level from 7.0 to 7.5, the pH adjustment dosage required would be:

pH Adjustment Dosage = 19.63 x (7.5 – 7.0 ÷ 0.2) = 98.15 pounds of pH increaser (such as sodium carbonate)

3. Alkalinity Adjustment Dosage: Total alkalinity refers to the ability of the pool water to resist changes in pH. The recommended total alkalinity level in a pool ranges from 80 to 120 ppm. To adjust the total alkalinity level of a pool, use the following formula:

Alkalinity Adjustment Dosage (in pounds) = Pool Volume (in gallons) x (Change in Alkalinity Desired ÷ 10)

For example, if you have an oval pool with a volume of 12,000 gallons and you want to increase the total alkalinity level from 70 ppm to 90 ppm, the alkalinity adjustment dosage required would be:

Alkalinity Adjustment Dosage = 12,000 x (90 – 70 ÷ 10) = 240 pounds of alkalinity increaser (such as sodium bicarbonate)

It’s important to note that these formulas are only general guidelines, and actual chemical dosages may vary depending on factors such as water temperature, bather load, and the type and condition of the pool equipment. It’s always a good idea to consult with a professional pool operator or chemical supplier to ensure proper dosages and procedures.