A pressure vacuum breaker must be installed how high above the flood level rim?

The correct height for installing a pressure vacuum breaker above the flood level rim is 12 inches. This requirement is part of plumbing codes designed to prevent back siphonage and ensure that any potential contaminants in potable water systems are not introduced.

The reason for this specific height is to provide adequate air gap, thus preventing any backflow of contaminated water. The 12-inch elevation creates a barrier that helps ensure that water cannot flow from the fixture back into the potable water supply in the event of a loss of pressure. This standard is essential for maintaining the safety and integrity of the drinking water system, following best practices in plumbing installations.

While there are other specified heights for different devices and situations in plumbing, the established height for a pressure vacuum breaker is specifically set at 12 inches to comply with health and safety regulations regarding water supply systems.