When should pH and disinfectant levels be tested?

The correct choice emphasizes the importance of testing pH and disinfectant levels at critical points to ensure the safety and quality of the pool water. Testing prior to opening allows for the establishment of appropriate chemical balance and ensures that levels are within the recommended range before swimmers use the facility. Conducting an additional test during operation ensures that any fluctuations in water chemistry can be addressed promptly, maintaining optimal water quality for swimmer safety.

Regular testing is crucial because pH and disinfectant levels can be affected by various factors like swimmer load, organic material introduced into the water, and environmental conditions. Having a strategy that includes testing before opening and during operation ensures that the pool is consistently safe and enjoyable for users while complying with health regulations. Regular checks can prevent potential issues such as algae growth and infection risks that may arise from improperly balanced water.

Other options suggest inadequate frequency for testing or ignore essential periods like the opening phase, which could leave the water in an unsafe condition for a prolonged time.