Zurn Wilkins 4-375OSY 4" Reduced Pressure Principle Assembly (RP) Open Stem & Yoke Lead-Free

Sale price$4,374.99

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Zurn Wilkins 4-375OSY 4" Reduced Pressure Principle Assembly (RP) Open Stem & Yoke Lead-Free

Zurn Wilkins 4-375OSY 4" Reduced Pressure Principle Assembly (RP), Open Stem & Yoke Gate Valves, Lead-Free, Flange x Flange Connection.

Product Overview:

The Zurn Wilkins 4-375OSY Reduced Pressure Principle Backflow Preventer provides high hazard protection for all applications. The flanged, epoxy coated ductile iron body is available with multiple shut-off valve options for installation versatility.

Features & Benefits:

  • 4" reduced pressure principle assembly with OS&Y gate valves
  • Short lay-length for small space installation
  • Ideal for any backflow replacement
  • Utilizes Zurn Wilkins low headloss compound check for reliable and superior performance
  • No threads or taps in body or cover, eliminating exposure to corrosion
  • Single access cover reduces downtime
  • NRS (standard), OS&Y, or Butterfly shut-off valves available
  • Available in flanged, grooved, or grooved x flanged end connections for installation versatility.

Product Specifications:

The Reduced Pressure Principle Backflow Prevention Assembly shall be certified to NSF/ANSI 61, ASSE® Listed 1013, and supplied with full port gate valves. The main body and access cover shall be epoxy coated ductile iron (ASTM A 536), the seat ring and check valve shall be NORYL™, the stem shall be stainless steel (ASTM A 276) and the seat disc elastomers shall be EPDM. The checks and the relief valve shall be accessible for maintenance without removing the device from the line. The Reduced Pressure Principle Backflow Prevention Assembly shall be a ZURN WILKINS Model 37


Designed for installation on potable water lines to protect against both backsiphonage and backpressure of contaminated water into the potable water supply. The Model 375 provides protection where a potential health hazard exists. Ideal for use where lead-free* valves are required.

Standards Compliance (Horizontal & Vertical):

  • ASSE® Listed 1013
  • IAPMO® Listed
  • CSA® Certified B64.4 (2 1/2" thru 8")
  • AWWA Compliant C511, and C550
  • FM® Approved
  • UL® Classified
  • C-UL® Classified
  • NYC MEA 49-01-M Vol 2 • Approved by the Foundation for Cross Connection Control and Hydraulic Research at the University of Southern California.
  • Meets the requirements of NSF/ANSI 61* (0.25% MAX. WEIGHTED AVERAGE LEAD CONTENT)


  • Main Valve Body: Ductile Iron ASTM A 536
  • Access Covers: Ductile Iron ASTM A 536
  • Coatings: FDA Approved Electrostatic Epoxy Finish
  • Internals: Stainless Steel, 300 Series NORYL™, NSF Listed
  • Fasteners: Stainless Steel, 300 Series
  • Seal Rings: EPDM (FDA approved)
  • O-rings: Buna Nitrile (FDA approved)
  • Sensing Line: Stainless Steel, Braided Hose


  • Sizes:  2 1/2"*, 3"*, 4", 6", 8", 10"
  • Maximum Working Water Pressure: 175 PSI
  • Maximum Working Water Temperature: 140°F
  • Hydrostatic Test Pressure: 350 PSI
  • End connections:
    • (Grooved for steel pipe) AWWA C606
    • (Flanged) ANSI B16.1 Class 125

Typical installation:

Local codes shall govern installation requirements. Unless otherwise specified, the assembly shall be mounted at a minimum of 12" (305mm) and a maximum of 30" (762mm) above adequate drains with sufficient side clearance for testing and maintenance. The installation shall be made so that no part of the unit can be submerge

Technical Documentation:

Zurn Wilkins 4-375OSY: Specification Submittal

Zurn Wilkins 4-375OSY: Installation and Maintenance Instructions (2-1/2" to 6")

Zurn Wilkins 4-375OSY: Installation and Maintenance Instructions (8" to 10")

Zurn Wilkins 4-375OSY: Repair Parts

Zurn Wilkins 4-375OSY: CAD Installation Drawing

Zurn Wilkins 4-375OSY: Relief Valve Discharge Rates


Zurn Wilkins 4-375A 4" Repair Video:

Zurn Wilkins Troubleshooting Reduced Pressure Principle Relief Valve Discharge Video:

Zurn Wilkins, Why Does Zurn Wilkins Call it a Compound Check Video:

Zurn Wilkins Compound Check Removal Video:

Cross Reference:

Zurn Wilkins 4-375A 4" Reduced Pressure Principle Assembly (RP) Non-Rising Stem Lead-Free Crosses:

  • Watts 009, 994, 995, 957
  • Conbraco 4D-200, RP4A
  • Febco 860, 867
  • Ames 4001SS, 400 Maxim 400 Colt

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