What type of device is required for backflow prevention in plumbing systems?

Backflow prevention is crucial in plumbing systems to protect the potable water supply from contamination. The correct choice is a backflow preventer or vacuum breaker, as these devices specifically serve the purpose of preventing the reverse flow of water. This reverse flow can occur due to changes in pressure within the plumbing system, which could lead to contaminants entering the clean water supply.

A backflow preventer is designed to ensure that water flows in one direction only, thus safeguarding against backflow incidents. Vacuum breakers, on the other hand, prevent the formation of a vacuum that could siphon water back into the supply line.

The other options do not fulfill the specific role of backflow prevention. A pressure relief valve is primarily used to release excess pressure in systems to prevent damage, a flow control device regulates the amount of fluid flowing through the system, and a sediment trap is used to collect debris and contaminants to prevent clogging. While these devices are important for different functions within plumbing systems, they do not provide backflow prevention.