A structure that allows a pipe to dip below an obstruction by forming a U-shaped path, forcing liquid to rise and exit the other end, is called an:

• A. Gate Valve Structure
• B. Torque Wrench
• C. Pathfinder
• D. Inverted Siphon

Answer: (D)

An inverted siphon is used when a sewer line must pass under an obstacle by dipping below it and then rising again on the other side. The liquid trapped in the pipe is driven by gravity, so it flows down into the low section and then climbs up to discharge, effectively carrying the flow under the obstruction. For it to work, the line must be kept full of liquid and properly vented to avoid air pockets that would break the siphon. This concept is different from a gate valve structure, a torque wrench, or a term like pathfinder, which are not descriptions of this flow path.