When installing plastic pipe underground, what is the maximum distance between supports that secure the pipe to the bottom of the trench?

For underground installations of plastic pipe, the maximum spacing between support systems is critical for ensuring the pipe's structural integrity and preventing sagging or damage. Plastic pipes, such as PVC or HDPE, require proper support to maintain their position as they are often subject to soil movement and hydrostatic pressure.

The maximum distance of 8 feet between supports is established in plumbing codes and industry best practices. This spacing helps to ensure that the pipe is sufficiently supported along its length, minimizing the risk of bending, which can lead to leaks or breaks. If the support spacing were too great, the flexibility of the pipe could lead to stresses and distortions, which compromise its functionality.

In line with this, the other options suggest distances that are either too short or too long. A spacing of 4 feet may provide excessive support, which is unnecessary and could increase installation costs. Distances of 10 feet or 12 feet increase the risk of sagging and potential failure of the pipe, thereby not meeting safety standards and performance expectations for underground installations. Therefore, the correct answer reflects both safety considerations and practical installation practices.