At what level in an underground fuel tank is the low-level shutoff set to deenergize the fueling pump motor before the pump runs dry?

The low-level shutoff for a fueling pump is designed to prevent the pump from running dry, which can cause damage to the pump and lead to operational failures. The industry standard for the low-level shutoff is typically set at approximately 13 inches. This level is determined based on the operational requirements of the pump and the need to maintain a minimum amount of fuel in the tank to lubricate and cool the pump components effectively. Setting the shutoff at 13 inches allows for adequate fuel to remain above the pump intake, ensuring that the pump operates efficiently and without the risk of cavitation or damage that comes from running dry.

In comparison to the other levels provided, 7 inches, 11 inches, and 18 inches do not align with standard practices for low-level shutoff settings. While lower levels may not provide sufficient fuel to the pump, leading to dry operation, a higher setting like 18 inches may unnecessarily restrict fuel availability and could lead to premature shutoff of pumping operations. Thus, the 13-inch threshold provides a balance between protecting the pump and maintaining operational effectiveness in fuel dispensing.