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 Backflow Prevention Assemblies
 Watts SilverEagle 757/757DCDA
Watts SilverEagle Series 757/757DCDA Backflow Prevention Assemblies are used to prevent backflow of non-health hazard pollutants that are objectionable but not toxic, from entering the potable water supply system.
Watts Series 757/757DCDA Backflow Prevention Assemblies may be installed under continuous pressure service and may be subjected to backpressure. The Series 757 consist of two independently operating check valves, two shut off valves, and four test cocks. The 757DCDA/757NDCDA are used primarily on fire line sprinkler systems when it is necessary to monitor unauthorized use of water.
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- Extremely compact design
- 70% lighter than traditional designs
- 304 (Schedule 40) stainless steel housing & sleeve
- Groove fittings allow integral pipeline adjustment
- Patented tri-link (757)/bi-link (757a) checks provide lowest pressure loss
- Replaceable check disc rubber
- Available for horizontal, vertical or N pattern installations
- Unmatched ease of servicability
- Available with grooved butterfly valve shutoffs
- 757 Sizes 2-1/2"-4" available with quarter-turn ball valve shutoffs
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Applications:
Watts 757 - Double Check Valve Assemblies are used to prevent backflow of non-health hazard pollutants that are objectionable but not toxic. Double checks may be installed under continuous pressure service and may be subject to backpressure. Double Check Valve Assemblies may be used in fire protection systems without chemical additives, industrial in-plant plumbing systems and other systems requiring non-health hazard protection. Local codes may vary, consult authorities for specific approved applications.
Watts 757DCDA - Double Check Detector Assemblies are used to prevent backflow of non-health hazard pollutants that are objectionable, but not toxic. Double Check Detector Assemblies may be installed under continuous pressure service and may be subject to backpressure. Double Check Detector Assemblies are used primarily on fireline sprinkler systems when it is necessary to monitor unauthorized use of water.
Normal Operation
In normal flowing operation, the independent torsion spring check remains closed until there is a water demand. Each check will then open and maintain an approximate 1psi differential in the direction of flow. In a nonflow or backflow condition, both checks will close until the resumption of normal flow.
Series 757/757DCDA Cutaway View - Full Flow Operation
Installation:
Most field problems occur because dirt or debris present in the system at the time of installation becomes trapped in the 1st check seating area resulting in a low or zero differential across the 1st check. The system should be flushed before the backflow valve is installed. If the system is not flushed until after the backflow valve is installed, remove both check modules from the valve and open the inlet shut-off to allow water to flow for a sufficient time to flush debris from the water line. If debris in the water system continues to cause fouling, a strainer can be installed upstream of the backflow assembly.
Watts Series 757 and 757DCDA may be installed in either a horizontal, vertical, or “N” position as long as the backflow assembly is installed in accordance with the direction of the flow arrow on the assembly and the local water authority approves the installation.
The assembly should be installed with adequate clearance around the valve to allow for inspection, testing, and servicing. Twelve inches should be the minimum clearance between the lower portion of the assembly and the floor or grade.
 
Interior Installation ------------------- Enclosure Installation
E-mail: nni_inc@hotmail.com
Phone: 305-687-3330
Toll Free: 1-877-NNI-FIRE (1-877-664-3473)
Fax: 305-687-3360
Copyright © 2001 NNI INC. All rights reserved.
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