Wherever a water main crosses a sewer line, the water main should be at least how many inches above or below the sewer line?

When a water main crosses a sewer line, the standard practice is to ensure that the water main is either at least 18 inches above or below the sewer line. This distance is crucial for preventing potential contamination of the potable water supply. Maintaining an adequate vertical separation helps to minimize the risk of sewer leaks or breaks affecting the water main, which could lead to cross-contamination. Water quality is a top priority in water distribution systems, and adhering to these specifications is a fundamental practice in safeguarding public health. The 18 inches provides a balance that effectively reduces the risk of backflow or other contamination risks while still being practical for installation and maintenance of both the water and sewer lines.