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Deringer 20 (DC)

Double Check Backflow Preventer

Deringer 20
MSRP: $8,019.00 MSRP: $8,019.00 As low as: $1,679.00
Price includes standard ground shipping.

The Deringer 20 Double Check Backflow Preventer prevents non-health hazard pollutants from entering a potable water supply system when backpressure and/or backsiphonage conditions occur.

The smallest, lightest, most economical, best performing, and only all stainless steel backflow preventer. Period.

Deringer Approvals

Deringer 20 Double Check Valve Assemblies are designed to prevent non-health hazard pollutants from entering the potable water supply system caused by backpressure and/or backsiphonage conditions.

Deringer 20

Maximum Working Pressure: 175psi (12.1 bar)
Temperature Range: 33 to 140 deg F (1 to 60 deg C)
Lead Free: 0.25% Maximum by Weight

End Connections:
Flange Adapters: ANSI B16.1 Class 125
IPS Groove for Steel Pipe: AWWA C606

Rate of Flow:

Rate of Flow Deringer 20


Deringer 20 measurements


Valve Housing: 304 Stainless Steel
Valve Cover: 304 Stainless Steel
SOV Disks: EPDM/304SS
SOV Shafts: 304 Stainless Steel
SOV Bearings: Teflon/Bronze
Non Wetted Bolts: Grade 8 Zinc Plated
Check Disks: Silicone
Wetted Fasteners: 18-8 Stainless Steel
Check Springs: 17-7 Stainless Steel
Check Pins: 17-7/18-8 Stainless Steel
Check Seats: Noryl Polymer
O-Rings: Buna-N

Engineering Specifications

The Deringer 20 Double Check (DC) valve shall utilize two independent Dual Action Check modules and two integral resiliently seated shut-off valves all of which shall be contained within a single rigid valve housing constructed entirely of 304 stainless steel. Both integral shutoff valves shall include pre-wired supervisory tamper switches contained within a weatherproof actuator housing approved for both indoor and outdoor use. Dual Action Check modules shall operate as a poppet style check under low flow conditions, operate as a swing style check under high flow conditions and utilize replaceable silicone elastomer sealing discs. Assembly test cocks shall be handle-less and operate via a tamper resistant actuator. Assembly shall have a single full access service port and cover with an inline replaceable elastomer seal. Assembly shall be serviceable without special tools and approved for both horizontal and vertical applications.

Deringer Specification Sheets

The Deringer 20 Specification Sheet includes information on valve characteristics, flow performance data, approval status and engineering specifications for all sizes. This file can be downloaded as a PDF and saved for future use.

Deringer 20 Specification Sheet

Maintenance Instructions

The Deringer 20/30 Maintenance Instructions provide step by step procedures for maintaining a 2 to 4 inch Deringer 20/30 backflow preventer. A printable PDF document and video of these instructions are both available.

Deringer 20/30 Maintenance Instructions

Maintenance Video - 2 to 4" Deringer 20

Tamper Switch Procedure

The Deringer Gear Box Tamper Switch Procedure provides a step by step instructions for positioning the wiring of the Deringer gear box for fire alarm protection. A printable PDF document of these instructions is available.

Tamper Switch Instruction

Gear Box Wiring Instructions

The Deringer Gear Box Wiring Installation Instructions provide step by step procedures for wiring the Deringer gear box for fire alarm protection. A printable PDF document of these instructions is available.

Gear Box Wiring

Gear Box Replacement

Indicator Flag Adjustment

The Indicator Flag Adjustment Instructions provides a step by step procedure for aligning the flag to fully open and fully close on the backflow preventor gear box. A printable PDF document of these instructions is available.

Indicator Flag Position

Dual-Action™ Check Modules

The Patented Dual-Action Check™ (US8875733) is the core technology behind the superior performance of Deringer Backflow Prevention Product Line. The Dual-Action Check™ combines all of the best features of industry standard “poppet” checks and “swing” checks into a single high performance check module.

  • Light weight engineered polymer components.
  • Modular for easy removal of complete check from body.
  • Easily disconnect spring tension for safe check servicing.
  • Replaceable Silicone Rubber Elastomer Disk.
  • Excellent resistance to fouling
Dual Action Check Module

Poppet Action

Low Flow Poppet Action


  • Initial 25% of check stroke is that of a poppet check
  • Consistent static sealing
  • Excellent resistant to fouling
  • Reliable check closure
  • Stable flow characteristics at lower flow rates

Swing Action


  • Final 75% of check stroke is that of a swing check
  • Minimal friction loss at high flow rates
  • More linear flow path water through valve.
High Swing Action

Bow-Seal™ Full Access Cover

The Patented Bow-Seal™ Full Access Cover (US8844562) is pre-formed to cylindrical shape friendly to high fluid pressure. This allows the cover to be much thinner and lighter than traditional flat covers while still providing FULL and EASY access to Dual Action™ Check Modules.

Additional features include:

  • Light weight Simple removal
  • No sliding seals
  • Full access to valve internals
  • No cumbersome and heavy couplings
Bow Seal Access Cover

Tamper Resistant Test Cock

The Deringer tamper resistant 1/2" and 3/4" ball valves are the first handle-less test cocks found on large diameter backflow devices in the industry. The top of the valve actuation stem has a unique shape that uses an independent custom wrench to open and close test cocks. All test cocks are lead free and meet the SDWA requirements.

Deringer Tamper Resistant Test Cock