What is the required tamped backfill under and around the pipe in trenches cut through rock?

The correct choice indicates that a 6-inch tamped backfill under and around the pipe in trenches cut through rock is necessary to provide adequate support and protection for the pipe. This measurement is crucial for several reasons.

Firstly, using a backfill of this thickness helps to create a stable bedding for the pipe, reducing the chances of movement or settling that could lead to stress or potential damage. Pipes installed in rocky trenches can be susceptible to various external forces, and a consistent and ample backfill ensures their integrity by distributing any load placed above the ground evenly.

Furthermore, a 6-inch layer allows for adequate compaction to reduce voids and increase the overall density of the backfill material, minimizing the risk of future erosion or shifting. This helps to maintain the proper alignment of the pipe over time, which is essential for optimal performance and to prevent leaks.

Overall, specifying a tamped backfill of 6 inches under and around the pipe in rocky conditions ensures durability and stability, which are critical in any sprinkler fitting application.