Maintenance Technician Practice Test 2026 - Free Maintenance Technician Practice Questions and Prep Guide

The most suitable type of pipe for installation deep underground is Schedule 120. This designation refers to the thickness and durability of the pipe walls, which are crucial factors when considering the high pressures and potential external stresses that can be encountered in deep underground applications. Schedule 120 pipes have a thicker wall compared to the other schedules, which provides greater resistance to crushing forces and soil pressure.

In underground installations, particularly in environments with shifting soil or where the pipe may be subject to heavy loads, having a more robust pipe can help prevent failures such as cracking or deformation. The added strength of Schedule 120 makes it especially valuable for these conditions, ensuring long-term reliability and integrity of the piping system without the frequent need for repairs or replacements that might be necessary if a weaker pipe were used.

While Schedule 40 and Schedule 80 also provide adequate strength for many applications, the superior thickness and pressure ratings of Schedule 120 make it the most advantageous choice in scenarios where maximum durability is essential.