At what pH level can a public pool be immediately closed by the department?

The correct choice reflects the minimum acceptable pH level for a public pool, which is typically around 7.2. When the pH of a pool drops to this level or below, it can cause discomfort to swimmers and can negatively impact the efficacy of chlorine, leading to potential health risks due to insufficient sanitation. Public health regulations often stipulate that if the pH level falls below this threshold, the pool must be closed immediately to ensure the safety and comfort of users.

Maintaining proper pH levels is crucial not just for swimmer safety, but also for the overall health of the pool environment and equipment. A pH that is too low can lead to corrosive conditions that can damage pool surfaces and equipment, which is another reason regulatory bodies enforce strict pH standards. In contrast, levels above this range may not lead to immediate closure but are monitored closely to ensure they do not compromise public health.