Journeyman Plumber Practice Exam 2025 – The Complete All-in-One Guide to Exam Success!

A vacuum breaker is specifically designed to prevent backsiphonage, which is a type of backflow that can occur when there is a drop in pressure in the supply line, causing contaminated water to be drawn back into the potable water supply. This scenario can happen during events such as water main breaks or when a high demand for water creates a negative pressure, effectively siphoning water from a connected source.

While backflow can encompass both backsiphonage and backpressure, a vacuum breaker specifically addresses the issue of backsiphonage. It works by allowing air to enter the system when the pressure drops, thus breaking the vacuum that could lead to contamination.

The other options, while related to the general topic of preventing contamination and ensuring safe drinking water, do not accurately capture the primary function of a vacuum breaker. Backpressure and cross-contamination are concerns in plumbing but are addressed through different means and devices.