Which test is performed with a mandrel during pipeline installation to assess deflection?

Which test is performed with a mandrel during pipeline installation to assess deflection?

• A. Hydrostatic test
• B. Manhole test
• C. Deflection test
• D. Sewer taps

Answer: (C)

Deflection control in installed sewer lines is checked by using a mandrel to measure how much the pipe has bent or shifted from its intended path. A mandrel, passed through the pipe, acts as a go/no-go gauge: if it passes freely within the allowed tolerances, the pipe’s alignment and curvature are acceptable; if it catches or binds, there’s excessive deflection that may require remediation. This test specifically targets how the pipe sits and bends in the ground, not whether it leaks or whether joints are sound. Hydrostatic testing looks for leaks by filling the line with water and pressurizing it, so it isn’t about deflection. A manhole test checks the integrity of manholes and their connections, typically with pressure or water, not the pipe deflection. Sewer taps refer to creating service connections, not testing installed pipe geometry.

Deflection control in installed sewer lines is checked by using a mandrel to measure how much the pipe has bent or shifted from its intended path. A mandrel, passed through the pipe, acts as a go/no-go gauge: if it passes freely within the allowed tolerances, the pipe’s alignment and curvature are acceptable; if it catches or binds, there’s excessive deflection that may require remediation. This test specifically targets how the pipe sits and bends in the ground, not whether it leaks or whether joints are sound.

Hydrostatic testing looks for leaks by filling the line with water and pressurizing it, so it isn’t about deflection. A manhole test checks the integrity of manholes and their connections, typically with pressure or water, not the pipe deflection. Sewer taps refer to creating service connections, not testing installed pipe geometry.