Certified Pool Operator Practice Test

To raise the free chlorine (FC) in a 20,000-gallon pool by 2.0 ppm, it would require __________ ounces of calcium hypochlorite.

1. 6

2. 8

3. 10

4. 12

The correct answer is: 6

Adding 6 ounces of calcium hypochlorite would raise the free chlorine level in a 20,000-gallon pool by 2.0 ppm. This is because calcium hypochlorite is a common pool shock treatment that contains approximately 65% available chlorine. This means that for every 1 ounce of calcium hypochlorite added, it will raise the chlorine level by approximately 0.65 ppm. Therefore, 6 ounces of calcium hypochlorite (0.65 ppm x 6 ounces) would provide 3.9 ppm of free chlorine, which would increase the FC level in a 20,000-gallon pool by approximately 2.0 ppm. The other options would not be enough to raise the FC level by 2.0 ppm; 8 ounces would provide 5.2 ppm, 10 ounces would provide 6.5 ppm and 12 ounces would provide 7.8 ppm. It is important to carefully measure and calculate the appropriate amount of calcium hypochlorite to avoid accidentally over-shocking the pool and causing potential damage or safety hazards.