In sewer maintenance, a 'pig' is most associated with which type of sewer operation?

• A. Building Sewer
• B. Gravity Sewer
• C. Storm Sewer
• D. Force Main

Answer: (D)

Pigs are devices driven through a pipeline by the pressure of the fluid to clean, separate debris, or inspect the line. They work best in a pressurized system because the water or air pressure actually pushes the pig along the pipe, allowing it to move through and perform its task. That’s why they’re most associated with a force main, which is a pressurized sewer line.

In gravity-based systems—such as gravity sewers and most building sewers—the flow relies on gravity rather than pressure, so there isn’t consistent propulsion to push a pig through the line. Storm sewers are typically not operated as pressurized mains either, so using a pig there isn’t practical.