California ICC UST Inspector Practice Exam

At what capacity must a ball float begin restricted flow for overfill prevention?

1. 96%

2. 85%

3. 90%

4. None of the above

The correct answer is: 90%

The capacity at which a ball float must begin restricted flow for overfill prevention is established to ensure that there is a safety buffer before the tank overflows. In the context of underground storage tanks (USTs), the use of a ball float mechanism helps to prevent overfilling by restricting the flow of liquid when a specific level is reached. The correct choice of 90% indicates that once the liquid in the tank reaches this level, the ball float mechanism activates to reduce flow, thereby preventing the tank from reaching a full state that could lead to overfilling and potential environmental hazards. This 90% threshold is a widely accepted standard in the industry, aligning with regulatory requirements designed to enhance the safety and integrity of fuel storage systems. Options outside of this standard, such as 96% or 85%, do not align with the established guidelines for overfill prevention, as they either allow for too little capacity before flow restriction occurs (in the case of 85%) or too much capacity (in the case of 96%), which increases the risk of overflow. The configuration of these systems is specifically engineered to initiate pressure relief and flow reduction at the 90% mark to ensure safety and compliance with regulations.