Massachusetts Plumbers Journeyman Practice Exam

What is the requirement for installing vacuum breakers in relation to the flood level rim of the fixture they serve?

1. Six inches below

2. Six inches above

3. At the same level as

4. Depends on the fixture size

The correct answer is: Six inches above

The requirement for installing vacuum breakers is that they must be positioned at least six inches above the flood level rim of the fixture they serve. This distance is crucial because vacuum breakers are designed to prevent backflow and contamination of the potable water supply. When installed too low, there is a risk that backflow could occur, especially during events such as a sudden drop in water pressure or when a fixture is drained rapidly, thereby creating a siphoning effect. By positioning vacuum breakers at a minimum of six inches above the flood level rim, the system ensures that there is a physical gap, which provides a reliable safety measure against potential contamination from the fixture. This standard is often codified in plumbing codes to safeguard public health.