Grade 4 Stationary Engineer License Practice Exam

The primary function of a vacuum breaker is to prevent backflow and protect against siphoning. Vacuum breakers are designed to allow air to enter a plumbing system when a negative pressure occurs. This action breaks the vacuum and prevents the backflow of potentially contaminated water into a clean water source. It is crucial in maintaining a safe water supply and ensuring that any harmful substances do not get drawn back into the main supply, which could occur in situations where siphoning takes place due to pressure changes.

In plumbing and other fluid systems, maintaining the integrity of the water supply is essential for health and safety. Vacuum breakers are strategically installed in systems where backflow could happen, ensuring that water flows in the correct direction and preventing any hazardous situations.

The other choices do not pertain to the fundamental role of a vacuum breaker. Increasing steam pressure relates to steam systems and does not involve backflow prevention. Regulating water levels typically refers to components like floats or level controllers, and enhancing heat transfer pertains to designs focusing on thermal efficiency rather than backflow prevention. Therefore, the choice highlighting the prevention of backflow accurately captures the purpose of a vacuum breaker.