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The 2" (Deringer 20) Kit is a double check valve that prevents non-health hazard pollutants from entering a potable water supply system when backpressure and/or backsiphonage conditions occur.

2" (Deringer 20) Kit Includes:
  • (1) 2½" Deringer 20
  • (2) 2½" Groove Couplings
  • (2) 2" NPT x 2½" Groove Adapter

End connections are union type stainless steel 2” female NPT threads for ease of installation. Entire valve housing is constructed of stainless steel (including shut off valves) for industry leading corrosion resistance.


Approved in the Horizontal & Vertical Up Position.

This valve is made to order. Lead time is 2-3 business days + shipping time.



Pro Price:

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Deringer Double Check Backflow Preventer DC Title
Deringer Double Check Backflow Preventer DC Cutaway

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

Deringer Double Check Backflow Preventer DC approvals
Maximum Working Pressure:
175psi (12.1 bar)
Temperature Range:
33° - 140°F (1° - 60°C)
End Connections
- IPS Groove for Steel Pipe:
- Flange Adapters:
ANSI B16.1 Class 125
Lead Free:
0.25% Maximum by Weight

Flow Performance

Deringer Double Check Backflow Preventer DC Flow Performance

Measures &  Materials

Deringer Double Check Backflow Preventer DC Measures and Materials
Valve Housing:
304 Stainless Steel
Valve Cover:
304 Stainless Steel
SOV Disks:
SOV Shafts:
304 Stainless Steel
SOV Bearings:
Non Wetted Bolts:
Grade 8 Zinc Plated
Check Disks:
Wetted Fasteners:
18-8 Stainless Steel
Check Springs:
17-7 Stainless Steel
Check Pins:
17-7/18-8 Stainless Steel
Check Seats:
Noryl Polymer

Engineering &  Specifications

TheDeringer 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.

Retrofit   Spool Program

The Backflow Direct Retrofit Program is the easiest spool ordering process in the industry!

Simply go to our online Retrofit Spool Form and submit a few pieces of needed information. Backflow Direct will take the information provided and create a CAD drawing of the completed retrofit package along with a quote for you to review.

When you are ready to order, simply confirm by email and BackFlow Direct will start your order. It really is THAT easy!

BackFlow Direct's retrofit program video provides an easy to understand demonstration of the ordering process from start to finish. Please feel free to contact us with any questions at [email protected]



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
Deringer Backflow Preventer Dual Action Check
Low Flow Poppet Action

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 2

Tamper Resistant  Test Cock

The Deringer tamper resistant ½” and ¾” 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 Backflow Preventer Tamper Resistant Test Cocks


Deringer 20 Specification sheet

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.

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Tamper Switch Instructions

Maintenance   Instructions

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

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Tamper Switch Instructions

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.

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Gear Box Wiring Instructions

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.

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Indicator Flag Adjustment Instructions

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.

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Backflow Direct Warranty

Product  Warranty

This printable document provides information for the Backflow Direct one year warranty for Deringer and Magnum backflow preventers.

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