Series 757a, 757aDCDA
757Na, 757NaDCDA
Double Check Valve Assemblies
Double Check Detector Assemblies
Sizes: 21⁄2" – 6" (65 – 150mm)
• Installation
• Service
• Repair Kits
• Maintenance
For field testing procedure, send for IS-TK-DL, IS-TK-9A,
IS-TK-99E and IS-TK-99D.
For other repair kits and service parts, send for PL-RP-BPD
and F-RK-DC.
For technical assistance, contact your local Watts representative.
Watts 757a OSY
IMPORTANT: Inquire with governing authorities for local installa-
tion requirements.
NOTE: For Australia and New Zealand: Pipeline strainers
should be installed between the upstream shutoff valve and the
inlet of the backflow preventer.
It's important that this assembly 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 sprinkler system, all mechanical checks, such as alarm checks and backflow preventers, should be flow tested and inspected internally
in accordance with NFPA 13 and NFPA 25.
RP/IS-757a/757aDCDA
Limited Warranty: Watts Regulator Co. (the “Company”) warrants each product to be free
from defects in material and workmanship under normal usage for a period of one year from
the date of original shipment. In the event of such defects within the warranty period, the
Company will, at its option, replace or recondition the product without charge.
THE WARRANTY SET FORTH HEREIN IS GIVEN EXPRESSLY AND IS THE ONLY WARRANTY
GIVEN BY THE COMPANY WITH RESPECT TO THE PRODUCT. THE COMPANY MAKES NO OTHER
WARRANTIES, EXPRESS OR IMPLIED. THE COMPANY HEREBY SPECIFICALLY DISCLAIMS ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
The remedy described in the first paragraph of this warranty shall constitute the sole and exclusive remedy for breach of warranty, and the Company shall not be responsible for any incidental, special or consequential damages, including without limitation, lost profits or the cost of
repairing or replacing other property which is damaged if this product does not work properly,
other costs resulting from labor charges, delays, vandalism, negligence, fouling caused by foreign material, damage from adverse water conditions, chemical, or any other circumstances over
which the Company has no control. This warranty shall be invalidated by any abuse, misuse,
misapplication, improper installation or improper maintenance or alteration of the product.
Some States do not allow limitations on how long an implied warranty lasts, and some States
do not allow the exclusion or limitation of incidental or consequential damages. Therefore the
above limitations may not apply to you. This Limited Warranty gives you specific legal rights,
and you may have other rights that vary from State to State. You should consult applicable
state laws to determine your rights. SO FAR AS IS CONSISTENT WITH APPLICABLE STATE
LAW, ANY IMPLIED WARRANTIES THAT MAY NOT BE DISCLAIMED, INCLUDING THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE LIMITED IN DURATION TO ONE YEAR FROM THE DATE OF ORIGINAL SHIPMENT.
2
Guidelines
Most field problems occur because dirt and debris present in
the system at the time of installation becomes 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 models 757a and 757aDCDA 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.
Note: Assembly body should not be painted.
Horizontal Installation
Vertical
Installation
“N” Pattern
Figure D
Figure E
Figure F
Figure A
Figure B
Figure C
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
1
⁄4-turn clockwise and 1⁄4-turn counter-clockwise 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.
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 disk 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.
Basic Installation Instructions
3
Test Procedures
Double Check Valve Assemblies
Test Check Valve No.1
Step 1: Ensure shutoff #1 is open, shutoff #2 is closed.
Step 2: Connect high side hose to test cock #3, low side to
test cock #2 and open both test cock #2 and test
cock #3.
Step 3: Open valve C, then open A to bleed air from the high
side. close valve a, then open B to bleed low side.
Close valve B.
Step 4: Connect vent hose loosely to test cock#1. Open valve
A to vent air from vent hose, Tighten vent hose at test
cock #1, open test cock #1.
Step 5: Close shutoff #1. Slowly loosen hose at test cock #2
until differential gauge rises to 2psi and retighten
hose. If the differential reading does not decrease,
record check valves as “tight”.
Test Check Valve No. 2
Step 1: Move the high side hose to test cock #4, low side to
test cock #3 and open both test cock #3 and test
cock #4. Remove vent hose from test cock #1, open
shutoff #1.
Step 2: Open valve C, then open valve A to bleed air from the
high side. Close valve A, then open valve B to bleed
low side. Close valve B.
Step 3: Connect vent hose loosely to test cock #1. Open
valve A to vent air from the vent hose. Tighten vent
hose at test cock #1, open test cock #1.
Step 4: Close shutoff #1, then slowly loosen hose at test cock
#3 until differential gauge rises to 2psi and retighten
hose. If the differential reading does not decrease,
record check as tight. Remove all hoses and restore
valve to original working condition.
Note: The assembly will fail both the first and second
check valve tests above, if shutoff #2 leaks excessively. To test for a leaky #2 shutoff, use the following procedure.
Test for Leaky No. 2 shutoff
Step 1: Connect the high side to test cock #1, low side to
test cock #4. Open test cock #1 and test cock #4.
Close shutoffs #1 and #2.
Step 2: Close valve C. Open valve A, then open valve B
1
⁄2
turn, loosen hose at test cock #4 to remove air.
Retighten hose.
Step 3: If the differential gauge rises above 0, there is exces-
sive leakage at shutoff #2 and it must be replaced to
test the assembly.
Ball Type Test Valves
A
C
B
Needle
Valve
High Hose
(Yellow)
Low Hose
White or Red
Vent Hose
(Blue)
Test Cock Test Cock Test Cock Test Cock
No. 1 No. 2 No.3 No.4
757a, 757aDCDA Repair Kits
Closure Sleeve Test Cock
with O-ring
Closure Sleeve
E-clip
Disc Elastomer
Second Check Module
Sleeve O-ring and Gasket
Check Module O-ring
First Check Module
ORDERING NO. SIZE DISC MODEL
1st Check Kits
0899250 21⁄2" - 4" EPDM RK 757a/757aDCDA CK1
0899251 6"
EPDM
RK 757a/757aDCDA CK1
Kit consists of: First check module, Check module O-ring,
Disc elastomer
2nd Check Kits
0899254 21⁄2" - 4" EPDM RK 757a/757aDCDA CK2
0899255 6"
EPDM
RK 757a/757aDCDA CK2
Kit consists of: Second check module, Check module O-ring,
Disc elastomer
ORDERING NO. SIZE DISC MODEL
1st or 2nd Check Rubber Parts Kits
0899258 21⁄2" - 4" EPDM RK 757a/757aDCDA RC4
0899259 6"
EPDM
RK 757a/757aDCDA RC4
Kit consists of: Check module O-ring, Disc elastomer and E-clip
1st or 2nd Check Cover Kits
0899266 21⁄2" - 4" – RK 757a/757aDCDA C
0899267 6"
–
RK 757a/757aDCDA C
Kit consists of: Closure sleeve, 2 pieces of sleeve O-ring
RP/IS-757a/757aDCDA 0910 EDP# 1915344
© 2009 Watts
USA: 815 Chestnut St., No. Andover, MA 01845-6098; www.watts.com
Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscanada.ca
A Watts Water Technologies Company
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