Questions? 916-760-4524


The 8" Deringer 20G Double Check 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.

Approved in the Horizontal & Vertical Up Position.

Important Note: Install with FLEX Couplings or Flange Adapters Only. DO NOT use RIDGED Couplings!

This valve is made to order. Lead time is 4-5 business days + shipping time.



Pro Price:

Write a review about this product ▶
Deringer Double Check Backflow Preventer DC Title
Deringer Double Check Backflow Preventer DC Cutaway

The Deringer 20G(X) 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

The Deringer 20G(X) Double Check Valve shall utilize two independent Dual Action Check modules contained within a single valve housing constructed entirely of 304 stainless steel. 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. Valve assembly shall include two resiliently seated and inline serviceable AWWA C509 gate valves of type outside yoke and stem (OS&Y). Both gate valves shall include a stainless steel stem with pre-machined groove for installation of supervisory tamper switches. 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 cover 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
Skewed View
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
Deringer Backflow Preventer Bow Seal Access Cover

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 20G Specification sheet

Deringer Specification Sheets

The Deringer 20G(X) 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.

Download pdf button

Deringer 20G Instructions

Maintenance   Instructions

The Deringer 20G(X)/30G(X) Maintenance Instructions provide step by step procedures for maintaining a 6" - 8” Deringer 20G(X)/30G(X) backflow preventer. A printable PDF document and video of these instructions are both available.

Download pdf button

Backflow Direct Warranty

Product  Warranty

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

Download pdf button View Video Button

WARNING: Cancer and Reproductive Harm -     Copyright © 2018 BackFlowDirect LLC, All Rights Reserved.