Which test checks deflection for plastic pipe by pulling a mandrel equal to 95% of the average diameter from downstream to upstream, with failure if deflection exceeds 5%?

Which test checks deflection for plastic pipe by pulling a mandrel equal to 95% of the average diameter from downstream to upstream, with failure if deflection exceeds 5%?

• A. Deflection Test: Go - No Go Test
• B. Lamping
• C. Dye Test
• D. Smoke Testing

Answer: (A)

A go/no-go deflection test for plastic pipe uses a mandrel sized to 95% of the pipe’s average inner diameter and pulls it through the installed line from downstream to upstream. The idea is to see if the pipe deflects (sags or deforms) more than the allowed 5%. If the mandrel passes freely, the deflection is within the 5% limit; if the mandrel binds, it means the pipe has deflected more than 5% and the installation fails. This test directly assesses whether the pipe maintains its intended shape and capacity after installation, without needing to excavate again. The other tests mentioned—lamping (visual inspection with light), dye test, and smoke testing—are used to detect leaks or obstructions, not to measure deflection.