In a reduced pressure backflow preventer, when does the relief valve open?

In a reduced pressure backflow preventer, the relief valve opens when the pressure in the reduction zone increases toward the supply pressure. This situation typically occurs under certain conditions, such as when the system experiences a reverse pressure condition or when the pressure downstream drops significantly.

The relief valve is a critical component of the backflow preventer, designed to protect the potable water supply from contamination. When upstream supply pressure exceeds the pressure in the reduced pressure zone due to backflow or other changes in the system, the relief valve automatically opens to discharge water, thus preventing the backflow of potentially contaminated water into the potable water supply.

Opening the relief valve under these circumstances helps maintain the integrity of the water system by allowing any excess pressure to escape, ensuring that the pressure differential remains safe and preventing contamination risks. This is why it is essential that the relief valve is correctly calibrated and functioning properly within such devices.