Zurn Wilkins 4-375OSY 4" Reduced Pressure Principle Assembly (RP) Backflow Preventer – OS&Y Gate Valves, Lead-Free, Flange x Flange

Product Overview

The Zurn Wilkins 4-375OSY Reduced Pressure Principle Assembly (RPZ) Backflow Preventer provides high hazard protection for potable water systems. With a flanged ductile iron body, OS&Y gate valves, and lead-free construction, it’s engineered to stop both backsiphonage and backpressure from introducing contaminants into drinking water.

Built with a short lay length for tight installations, a low headloss compound check for improved performance, and a single access cover for easier servicing, the 4-375OSY is a proven choice for commercial and industrial backflow prevention.

Features & Benefits

• 4" RPZ Backflow Preventer with OS&Y gate valves for maximum reliability

• Short lay length simplifies installation in confined spaces

• Low headloss design improves flow performance in demanding systems

• Epoxy-coated ductile iron body resists corrosion and extends service life

• Single access cover allows quick maintenance without full disassembly

• Flexible connection options with flange x flange ends

• Lead-free compliant to meet potable water standards

Specifications

• Size: 4"

• End Connections: Flanged, ANSI B16.1 Class 125

• Maximum Working Pressure: 175 PSI

• Maximum Temperature: 140°F

• Hydrostatic Test Pressure: 350 PSI

• Body Material: Ductile Iron, ASTM A 536 with FDA-approved epoxy finish

• Internals: Stainless steel, NORYL™, EPDM seals, Buna-N O-rings

• Sensing Line: Stainless steel braided hose

• Shutoff Valves: OS&Y gate valves (lead-free)

• Certifications:

  • ASSE® 1013

  • AWWA C511 & C550

  • IAPMO® Listed

  • CSA® Certified

  • UL® Classified / C-UL® Classified

  • FM® Approved

  • USC FCCCHR Approved

  • Meets NSF/ANSI/CAN 61 (≤0.25% weighted average lead content)

Installation Tips

• Install in accordance with local codes and plumbing standards.

• Mount assembly 12"–30" above floor drains with adequate clearance for testing and service.

• Ensure relief valve discharge is piped to a safe drainage point.

• Avoid submersion of any part of the assembly.

• Test the backflow preventer upon installation and perform routine annual testing.

FAQs

Q: What type of protection does the 4-375OSY provide?
A: It protects potable water systems from high hazard backflow conditions, including both backsiphonage and backpressure.

Q: Can this unit be installed in tight spaces?
A: Yes, its short lay length design makes it ideal for confined installation areas.

Q: Are the OS&Y gate valves included?
A: Yes, this model comes with flanged OS&Y shutoff valves.

Q: Is it compliant with lead-free potable water standards?
A: Yes, it meets NSF/ANSI/CAN 61 requirements with ≤0.25% weighted average lead content.

Q: How often should it be tested?
A: Backflow preventers should be tested at installation and at least annually to maintain compliance.