A device used to test the percent deflection in a sewer pipe between manholes is known as what?

A device used to test the percent deflection in a sewer pipe between manholes is known as what?

• A. poly pig
• B. air plug
• C. mandrel assembly
• D. laser

Answer: (C)

Testing percent deflection in a sewer line uses a tool designed to gauge the interior diameter along a run between manholes. A mandrel assembly is built for that purpose: it is pulled through the pipe and the clearance between the mandrel and the pipe wall indicates how much the pipe has deflected from a true circle. By comparing the measured clearance to the pipe’s nominal diameter, you can calculate the percent deflection. This method is standard because it directly assesses the pipe’s structural integrity over the straight, long section between manholes where deflection can develop from settlement or loading. Other tools don’t measure this deflection in the same way. A poly pig is used mainly for cleaning and inspecting the line, not for gauging interior diameter changes. An air plug seals sections for pressure or air testing, not to determine deflection. A laser measures alignment or surface features but isn’t the typical device used to quantify percent deflection in sewer pipes.

Testing percent deflection in a sewer line uses a tool designed to gauge the interior diameter along a run between manholes. A mandrel assembly is built for that purpose: it is pulled through the pipe and the clearance between the mandrel and the pipe wall indicates how much the pipe has deflected from a true circle. By comparing the measured clearance to the pipe’s nominal diameter, you can calculate the percent deflection. This method is standard because it directly assesses the pipe’s structural integrity over the straight, long section between manholes where deflection can develop from settlement or loading.

Other tools don’t measure this deflection in the same way. A poly pig is used mainly for cleaning and inspecting the line, not for gauging interior diameter changes. An air plug seals sections for pressure or air testing, not to determine deflection. A laser measures alignment or surface features but isn’t the typical device used to quantify percent deflection in sewer pipes.