Massachusetts Plumbers Journeyman Practice Exam 2026 – All-in-One Guide to Master Your Licensing Test!

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.