Reduced-Pressure Zone Backflow Preventers

Reduced-Pressure Zone (RPZ) Backflow Preventers are a crucial component in municipal water treatment systems. They provide a safeguard against the contamination of potable water supplies by preventing the backward flow of water from a potentially polluted source into the clean water supply.

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The RPZ Backflow Preventer works by maintaining a differential pressure zone that is lower than the supply pressure, hence the name "reduced-pressure." If backflow occurs, the reduced pressure zone allows any unwanted substances to be discharged out of the system, maintaining the purity of the water supply.

• Municipal water supply systems
• Irrigation systems
• Fire sprinkler systems
• Industrial process water systems within the municipal context

• Routine operation tasks include regular inspection to ensure proper operation and no leakage.
• Maintenance procedures involve yearly testing of the device by a certified professional to ensure that it is functioning correctly.
• Safety considerations include monitoring for continuous discharge, which can indicate a malfunction and potential risk of contamination.

• Pressure Differential Relief Valve: Central part of the RPZ, maintains the reduced pressure zone and discharges any backflow.
• Check Valves: Prevent the reverse flow of water. The first check valve reduces the supply pressure, and the second prevents backflow into the clean water supply.
• Shut-off Valves: Usually installed on either side of the RPZ device for maintenance purposes.

• The primary sizing parameter for an RPZ Backflow Preventer is the diameter of the pipe in which it will be installed.
• The pressure and flow rate of the water supply system should also be considered.

• MasterFormat Division 22 - Plumbing, Section 22 11 13 - Facility Water Distribution Piping

• Watts: Model 909 RPZ
• Febco: Series 825Y RPZ
• Zurn: Model 375XL RPZ

• Double Check Valve Assemblies: Similar function but cannot relieve pressure, making them less suitable for high-risk contamination areas.
• Atmospheric Vacuum Breakers: Simpler and more economical but not suitable for high hazard applications due to lack of pressure control.