Compaction is required for the first _____ inches of backfill above a pipe installed in a trench.

Compaction is an essential practice in plumbing and construction to ensure the stability and proper functioning of buried utilities, including pipes. The first 12 inches of backfill above a pipe installed in a trench must be compacted to prevent future settling and to protect the pipe from damage due to soil shifting.

When backfilling, loose soil can create voids or inconsistencies that lead to problems like pipe misalignment, crushing, or joint separation. Compaction within this initial 12-inch layer helps achieve an adequate density that will support the weight of the material above it and any loads from traffic or structures nearby. It also minimizes the risk of erosion and voids that might develop over time, leading to costly repairs or replacements. Proper backfill technique, especially within the first foot, is crucial for ensuring the long-term integrity of the piping system.

In practice, various methods such as mechanical compactors or tamps may be used to achieve the required compaction, ensuring that the area is uniformly packed down.