Which of the following is a main reason for weekly pool shocking?

Weekly pool shocking is primarily conducted to control algae growth and bacteria. This process involves adding a high dose of chlorine or other disinfectants to the pool water, which significantly raises the free chlorine levels and helps eliminate contaminants. Algae and bacteria thrive in conditions of improper sanitation and inadequate chlorine levels; therefore, shocking disrupts their growth and helps maintain a healthy swimming environment.

While maintaining aesthetic appearance is important, it is not the primary purpose of shocking. The clarity of pool water often improves as a result of proper disinfection, but this is a secondary benefit. Similarly, decreasing calcium hardness and raising pH levels are unrelated to the shocking process. Calcium hardness is managed by balancing the water chemistry rather than through shocking, and raising pH levels is achieved with different chemicals designated for that purpose. Thus, the main reason for weekly pool shocking is to safeguard against algae and harmful bacteria.