In pipeline installation, which test is used to evaluate pipe deflection when using a mandrel?

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

Answer: (B)

Deflection testing uses a mandrel to check how far an installed pipe has deflected from straight alignment. A mandrel is a tool sized to the allowable interior diameter of the pipe; when you pull it through the pipe, you’re essentially testing whether the pipe has bent or settled enough to reduce its interior clearance. If the mandrel passes with the expected clearance, the pipe is within the allowable deflection limits. If it binds or drags, that indicates excessive deflection or deformation that could affect flow or structural performance, signaling the need for repair or adjustment.

Hydrostatic tests are about sealing and leaking by filling the pipe with water under pressure; manhole tests evaluate joints and airtightness of manholes; sewer taps are about creating or inspecting lateral connections. None of those assess how much the pipe has deflected, which is why the deflection test with a mandrel is the correct choice.