When installing a horizontal soil line, a clothes washer branch connection may not be connected closer than how many feet downstream from a water closet opening?

The correct answer is based on plumbing codes that are designed to prevent cross-contamination and maintain an effective drainage system. When installing a horizontal soil line, connecting a clothes washer branch too close to the opening of a water closet can lead to potential issues such as backflow or siphoning, which can introduce contaminated water from the soil line into the washing machine's supply.

The requirement to have a minimum distance of five feet downstream from a water closet opening for a clothes washer branch connection is established to ensure there is enough distance to allow for proper flow and grading in the piping system. This distance helps mitigate the risk of negative pressure or backflow conditions that could negatively impact the performance of both the washer and the water closet.

By adhering to this standard, plumbing systems become safer and more effective, ensuring that all appliances function optimally without risking contamination or drainage issues.