Watts 757N User Manual
Installation, Maintenance, & Repair
Series 757, 757DCDA & LF757DCDA
Double Check Valve Assemblies
Double Check Detector Assemblies
Sizes: 21⁄2" – 10" (65 – 250mm)**
!
WARNING
Read this Manual BEFORE using this equipment.
Failure to read and follow all safety and use information can
result in death, serious personal injury, property damage, or
damage to the equipment.
Keep this Manual for future reference.
!
WARNING
You are required to consult the local building and plumbing
codes prior to installation. If the information in this manual
is not consistent with local building or plumbing codes,
the local codes should be followed. Inquire with governing
authorities for additional local requirements.
!
WARNING
Need for Periodic Inspection/Maintenance: This product must
be tested periodically in compliance with local codes, but at least
once per year or more as service conditions warrant. If installed on
a fire suppression system, all mechanical checks, such as alarms
and backflow preventers, should be flow tested and inspected in
accordance with NFPA 13 and/or NFPA 25. All products must be
retested once maintenance has been performed. Corrosive water
conditions, and/or unauthorized adjustments or repair could render
the product ineffective for the service intended. Regular checking
and cleaning of the product’s internal components helps assure
maximum life and proper product function.
NOTICE
For Australia and New Zealand, line strainers should be installed
between the upstream shutoff valve and the inlet of the backflow preventer.
Installation Guidelines
Most field problems occur because dirt and debris present in the
system at the time of installation become trapped in the #1 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 shutoff 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/LF757DCDA may be installed in
either horizontal or vertical 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. 12"
should be the minimum clearance between the lower portion of the
assembly and the floor or grade.
NOTICE
Assembly body should not be painted.
757 OSY
RP/IS-757/757DCDA
®
Testing
For field testing procedure, refer to Watts installation sheets
IS-TK-DP/DL, IS-TK-9A, IS-TK-99E and IS-TK-99D found on
www.watts.com.
For other repair kits and service parts, refer to our Backflow
Prevention Products Repair Kits & Service Parts price list
PL-RP-BPD found on www.watts.com.
For technical assistance, contact your local Watts representative.
** Metric Dimensions are nominal pipe diameter. This product is
produced with ASME/ANSI flanged end connections.
Horizontal Installation
Maintenance Instructions
21/2" – 6" (65 – 150mm)
Vertical
Installation
N Pattern
Figure A
Figure D
!
WARNING
Prior to servicing any Watts valve, it is mandatory to shut down
the water system by closing both the inlet and outlet shutoff
valves. After shutoff valves are closed, open test cock #2, #3
and #4 to relieve pressure within the backflow assembly.
1. After #3 test cock has been opened to relieve pressure,
remove #3 test cock from housing. (Figure A)
2. Insert a #3 screwdriver through the hole on the top of the
cover sleeve and using both hands rotate the cover sleeve
approximately
wise to break the sleeve O-ring seals. Using the screwdriver,
slowly slide the cover sleeve to the downstream side of the
housing. (Figure B)
3. Remove the stainless steel check retainer from the housing.
(Figure B)
4. Remove the #1 check module (Figure C) by inserting two flat
blade screwdrivers into the slots on either side of the check
module and gently pry the check module toward the open
zone.
5. Remove #2 check module with the same instructions as in #4
above. For servicing 6" (150mm) checks, see 8" – 10" (200 –
250mm) instructions on p. 3.
1
/4-turn clockwise and 1/4-turn counterclock-
Figure E
Figure B
6. To clean or inspect either check module, insert a #3 screwdriver through the downstream side of the check module as
shown in Figure D and E. When the screwdriver is in place,
remove the E-clip (Figure F) and pin connecting the structural
members and the check clapper will open with no tension.
7. Thoroughly clean the seating area. The sealing disc may be
removed, if necessary, by removing the screws connecting
the keeper plate to the clapper. The sealing disc may be
reversed and reinstalled if the elastomer is cut or damaged.
8. Wash check module and O-ring and inspect for any damage.
If damaged, reinstall new parts.
9. After thorough cleaning, lubricate O-ring w/FDA approved
lubricant, replace pin and E-clip in structural members,
remove screw driver and reinstall check modules and assemble housing in reverse order of these instructions.
Figure C
Figure F
2
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