What slope is required for underground product lines and vapor return lines towards the tank?

A uniform slope of not less than 1/8 inch per foot is required for underground product lines and vapor return lines towards the tank to ensure proper drainage and to prevent the accumulation of liquids, which can lead to product quality issues or even system failures. This specific design criterion helps avoid the risk of liquid pooling within the lines, which can cause operational problems such as phase separation or contamination of the fuel, as well as potential leaks or backflow issues. By maintaining this slope, the integrity of the entire storage system is supported, ensuring efficient operation and safety compliance with regulatory standards. Proper drainage also aids in minimizing the chances of environmental contamination in the case of a system failure, making it an essential aspect of UST management practices.