How an RPZ Valve Works
An RPZ valve protects the water supply using a pressure differential and a relief path to atmosphere. Here is how the components work together.
The principle
Water enters through the first check valve into a chamber kept at a lower pressure than the incoming supply — the reduced pressure zone. It then passes through the second check valve to the downstream system. Under normal conditions both check valves are open and water flows freely.
If the supply pressure drops, or downstream pressure rises above supply pressure, the relief valve opens. Water from the zone is discharged to atmosphere through the relief port, so any contaminated water is dumped rather than reaching the mains. Because the zone is open to atmosphere during a fault, reverse flow into the supply is prevented.
Watch it in action
See how an RPZ valve operates and protects the water supply in this short walkthrough.
Main internal components
First check valve
Allows water to flow into the reduced pressure zone and closes against reverse flow.
Second check valve
Allows water to flow out to the downstream system and closes against reverse flow.
Relief valve
Sits between the two check valves. Opens to atmosphere if pressure in the zone drops, discharging water safely.
Reduced pressure zone
The chamber between the two check valves, kept at a lower pressure than the supply to create the protective differential.
Test cocks
Small ports used to connect test equipment during annual testing.
Isolation valves
Allow the assembly to be isolated for maintenance and testing.
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