Watts 757a Series User manual

Series 757a/757aDCDA
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.
Its important that this assembly be tested periodically in com-
pliance with local codes, but at least once per year or more as
service conditions warrant. If installed on a fire sprinkler sys-
tem, all mechanical checks, such as alarm checks and back-
flow preventers, should be flow tested and inspected internally
in accordance with NFPA 13 and NFPA 25.
RP/IS-757a/757aDCDA
Limited Warranty: Watts Regulator 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. This 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 dam-
aged 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 or
improper installation of the product. THIS WARRANTY IS IN LIEU OF ALL OTHER WAR-
RANTIES, EXPRESS OR IMPLIED, INCLUDING ANY IMPLIED WARRANTIES OF MER-
CHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Any implied warranties that
are imposed by law are limited in duration to one year.
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.

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.
Horizontal Installation
Vertical Installation
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. 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 to 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 screw-
driver 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 structur-
al 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 dam-
age. 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.
Maintenance 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 exces-
sively. To test for a leaky #2 shutoff, use the follow-
ing 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
AC
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 MODEL
1st Check Kits
0899250 2
1
⁄ 2 " - 4" RK 757a/757aDCDA CK1
0899251 6" RK 757a/757aDCDA CK1
Kit consists of: First check module, Check module O-ring,
Disc elastomer
2nd Check Kits
0899254 2
1
⁄ 2 " - 4" RK 757a/757aDCDA CK2
0899255 6" RK 757a/757aDCDA CK2
Kit consists of: Second check module, Check module O-ring,
Disc elastomer
ORDERING NO. SIZE MODEL
1st or 2nd Check Rubber Parts Kits
0899258 2
1
⁄ 2 " - 4" RK 757a/757aDCDA RC4
0899259 6" RK 757a/757aDCDA RC4
Kit consists of: Check module O-ring, Disc elastomer and E-clip
1st or 2nd Check Cover Kits
0899266 2
1
⁄ 2 " - 4" RK 757a/757aDCDA C
0899267 6" RK 757a/757aDCDA C
Kit consists of: Closure sleeve, 2 pieces of sleeve O-ring
Watts USA Website: www.wattsreg.com • Watts Canada Website: www.wattscda.com
RP/IS-757a/757aDCDA 0230 EDP# 1915344 © Watts Regulator Co., 2002 Printed in U.S.A.