InterNACHI Plumbing Practice Exam 2025 - Free Plumbing Practice Questions and Study Guide

The correct answer indicates that the maximum horizontal spacing for PVC drainage pipe is 4 feet. This spacing guideline is essential for ensuring proper support and stability of the pipe, minimizing the risk of sagging or bending over time. Adequate support prevents stress on the joints and connections, which can lead to leaks or failures in the drainage system.

In plumbing systems, maintaining appropriate distances between hangers or supports is critical for the longevity and functionality of the piping. PVC pipes, being lightweight and less rigid compared to metal options, require closer spacing for support. The 4-foot interval allows for adequate reinforcement while considering the potential for movement due to temperature changes and the weight of the materials being drained.

Remember that these standards can vary based on local building codes and specific system requirements, so it is always recommended to consult the relevant plumbing code where the installation is taking place.