A plumber is installing a hot water recirculation system in a large custom home. The system utilizes a dedicated return line with a circulator pump. To prevent the mixing of hot water from the recirculating line with the cold water supply when there is no demand, which of the following backflow prevention methods is most appropriate at the point where the recirculation line ties back into the cold water supply?

Question: A plumber is installing a hot water recirculation system in a large custom home. The system utilizes a dedicated return line with a circulator pump. To prevent the mixing of hot water from the recirculating line with the cold water supply when there is no demand, which of the following backflow prevention methods is most appropriate at the point where the recirculation line ties back into the cold water supply?

Answer options: ✅ Atmospheric Vacuum Breaker (AVB)

• Pressure Vacuum Breaker (PVB)
• Double Check Valve Assembly (DCVA)
• Reduced Pressure Principle Backflow Preventer (RP)

Correct answer: Atmospheric Vacuum Breaker (AVB)

Explanation: An Atmospheric Vacuum Breaker (AVB) is suitable for preventing back-siphonage in recirculating lines where there is no continuous pressure and the device is installed at least 150 mm above the flood level rim of the fixture. PVBs and DCVAs are typically used for higher hazard applications or involve continuous pressure, while an RP device is for high-hazard cross-connections.