What distance between two plumbing systems ensures regulatory compliance?

The correct choice, which states that a distance of 5 feet of undisturbed soil is required between two plumbing systems to ensure regulatory compliance, aligns with plumbing codes designed to maintain sanitary conditions and prevent contamination. This specific distance is critical because it helps minimize the risk of cross-contamination between potable water lines and wastewater lines, a vital concern in plumbing design.

The regulation typically highlights that this safety buffer allows for the proper separation of potentially harmful contaminants from clean water sources, thereby protecting public health. Undisturbed soil is preferred over compacted or layered soil due to its ability to provide a natural barrier that can effectively manage gradients and drainage, reducing the likelihood of leaks or seepage that could compromise separations.

The other options do not meet the specific requirements set forth in common plumbing codes and standards, which focus on maintaining at least a 5-foot distance of undisturbed soil to ensure that both systems are safely distanced to protect the integrity of the water supply.