What is the minimum diameter of vapor return lines after the first manifold from the dispenser?

The minimum diameter of vapor return lines after the first manifold from the dispenser should be 3 inches to ensure adequate vapor recovery during the refueling process. This specification is crucial because it allows for the effective transportation of vapors that can be displaced during the refueling of vehicles. A larger diameter, specifically 3 inches, helps minimize restrictions that could lead to vapor backup and pressure buildup, which might otherwise compromise the efficiency of the vapor recovery system.

Using a diameter smaller than this could result in increased resistance to vapor flow, which may lead to ineffective vapor recovery and increased emissions. The design and installation of vapor recovery systems adhere to industry standards that prioritize both safety and environmental protection, ensuring that vapor return lines are sufficiently sized for optimal performance.