California ICC UST Service Technician Practice Exam

Overfill protection notifies the operator when the tank reaches what level of capacity?

1. 70% capacity

2. 80% capacity

3. 90% capacity

4. 100% capacity

The correct answer is: 90% capacity

Overfill protection systems are designed to prevent the overflow of liquids from storage tanks, particularly for underground storage tanks (USTs). The primary function of these systems is to notify operators when the tank reaches a predetermined level that is considered safe to ensure containment and prevent environmental hazards. In the context of USTs, the correct level of capacity where overfill protection activates is typically set at 90% of the tank’s total capacity. This margin allows for a buffer to account for factors such as thermal expansion of the liquid inside the tank and minimizes the risk of overflow during the filling process. When the tank reaches this 90% level, the overfill protection system triggers an alert to the operator. This alert system ensures that the operator can take necessary actions to prevent spillage and maintain compliance with environmental regulations, thereby protecting the environment and human health. Choosing a threshold lower than 90% could lead to physical limitations or operational challenges, while selecting a higher level, such as 100%, would significantly increase the risk of overflow rather than mitigate it. Therefore, the implementation of overfill protection at 90% capacity is a critical safety measure in tank management.