Cross Connection Specialist General Practice Test

The key idea is that an RPZ relief valve acts to protect the potable water supply from backflow by venting whenever the pressure on the downstream side drops too low relative to the upstream side. When the differential between the inlet and the downstream chamber falls below its set point, the relief valve opens to relieve that low differential, preventing a siphon or backflow that could draw contaminants into the supply. It’s not triggered by a large differential, nor by downstream pressure simply being higher than inlet, nor by a lack of flow, so those conditions don’t cause the relief valve to open.