Massachusetts Plumbers Journeyman Practice Exam

What is a vertical loop of pipe that prevents back-siphonage from occurring in the potable water supply pipe?

1. Air Gap (Drainage System)

2. Barometric Loop

3. Developed Length

4. Trap Seal

The correct answer is: Barometric Loop

The correct choice identifies a barometric loop as a critical method to prevent back-siphonage in potable water systems. A barometric loop is specifically designed to create a vertical rise and drop in the piping, which helps to maintain the necessary pressure and thus prevents negative pressure that can cause back-siphonage. This design effectively stops any contaminants from being drawn back into the clean water supply, adhering to health and safety regulations for drinking water systems. An air gap, while also a method of preventing contamination, functions differently by creating a physical separation between water in a system and potential contaminants, rather than through a vertical arrangement of pipes. Developed length relates to pipe layout and does not prevent back-siphonage but rather refers to the total length a fluid travels through pipe systems. A trap seal is typically associated with drainage systems to maintain a water seal within traps, preventing sewer gases from entering buildings, rather than addressing back-siphonage in potable water supplies.