FEB 765 Owner's manual
INSTALLATION, OPERATION, MAINTENANCE
IOM-F-765
Operation and Maintenance Manual
Pressure Vacuum Breaker
Model 765
Read and understand this
manual prior to installing,
operating or servicing this
equipment.
Model 765
Table of Contents
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Typical Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Service Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pressure Vacuum Breaker – Model 765. . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Troubleshooting Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Installation
1. The Pressure Vacuum Breaker Assembly
must be installed where it is accessible
for periodic testing or repair.
2. The device must not be installed in a
pipe line until the line has been flushed
of foreign material. Failure to flush the
lines completely may cause the check
members to become fouled and require
disassembly and cleaning.
3. The device must be installed so that the Air Inlet operates in the verti-
cal position (see diagrams). Installation in any other manner will cause
the device to malfunction.
4. The device should be installed where some spillage is not objection-
able, as instantaneous siphon conditions and pressure surges will
cause “spitting.”
5. When threading the device in line, place wrench only on ball valve hex
ends. Keep pipe dope off interior surfaces of valve.
6. After installation, open inlet ball valve to pressurize device. Slowly open
outlet ball valve to fill down-stream line.
NOTE: The downstream pressure must be maintained above 5psi to
keep the spring loaded air inlet poppet closed. If check valve fails to
hold 10psi minimum, it has become fouled and must be cleaned. Close
both ball valves and bleed pressure from device before disassembly.
Refer to Maintenance Manual for proper service methods.
NOTE: All devices are factory tested for proper operation. Any damage
caused by pipe line debris or improper installation is not included in the
product warranty. In case of malfunction, or possible warranty claim,
DO NOT REMOVE DEVICE FROM LINE. Contact your local FEBCO
Representative.
7. THE DEVICE MUST BE PROTECTED FROM FREEZING. Thermal
water expansion and/or water hammer downstream of the backflow
preventer can cause excessive pressure increases. Excessive pressure
situations should be eliminated to avoid possible damage to the system
and device. See recommended freeze protection procedures. (Freeze
Protection 765—Technical Sheet FP765)
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2
PRESSURE VACUUM BREAKER
765 – Field Testing Procedure
Equipment Required For Test:
Sight Tube Test Kit (1" clear plastic Sight Tube about 40" long with appro-
priate fittings to attach to Testcocks of Vacuum Breaker.)
Purpose of Test: (see diagram)
To test the Air Inlet and the Check Valves for proper performance.
Test Air Inlet:
The Air Inlet should be
tested to verify opening
above 1psi.
1. Remove Canopy from
top of Vacuum Breaker to
expose Air Inlet.
2. Install Sight Tube at
Testcock #2.
3. Close Ball Valve B on
discharge side of Vacuum
Breaker.
4. Open Testcock #2 and fill
tube to about 30" above
poppet. Close Testcock
#2.
5. Close Ball Valve A on Inlet side of Vacuum Breaker.
6. Slowly open Testcock #2 watching poppet in Air Inlet. Poppet must
unseat. If the Air Inlet does not open, it is sticking and must be repaired.
Close Testcock #2 and remove sight tube.
Test Check Valve:
The Check Valve should be tested to hold against 1psi in the direction of
flow.
1. Install Sight Tube at Testcock #1.
2. Open Ball Valve A to allow unit to refill with water.
3. Open Testcock #1 and allow Sight Tube to fill about 30" above top of
unit, then close Testcock.
4. Close Ball Valve A. (Ball Valve B should already be closed.)
5. Open Testcock #1.
6. Open Testcock #2. Water may run from Testcock #2 initially, but should
not continue. The level of water in the Sight Tube may drop a little, but
should not drop below 28" above the Check Valve. (Centerline of the
Sight Tube
Testcock #2
T
estcock #1
Ball Valve B
Ball Valve A
Canopy
Discharge Ball Valve.) If the level in the Sight Tube continues to drop
and water continues to run out of Testcock #2, the Check Valve is leak-
ing and should be repaired.
7. Close Testcocks #1 and #2.
Restore Operation:
1. Restore all Valves and Testcocks to their original positions and replace
Canopy.
Service Procedure
General service instructions applicable to all
sizes.
a. Rinse all parts with clean water prior to assembly.
b. DO NOT USE ANY PIPE DOPE, OIL, GREASE OR SOLVENT ON
ANY PARTS unless instructed to do so.
c. Do not force parts. Parts should fit freely together. Excess force may
cause damage and render the device inoperable.
d. Carefully inspect seals, seating surfaces, etc. for damage or debris.
e. Test unit after servicing to ensure proper operation.
f. Tighten canopy nut only until canopy cannot turn freely.
g. Rapidly open inlet ball valve to minimize spillage through the air vent.
Slowly open outlet ball valve.
h. Test unit to ensure proper operation.
i. Test unit after servicing to ensure proper operation.
j. Refer to applicable parts list and figures for visual aid information.
A. Model 765 - 1/2" through 1 1/4" sizes
1. Disassembly Bonnet/Poppet
a. Close outlet ball valve then close inlet ball valve. Bleed residual pres-
sure by opening #2 testcock.
b. Remove canopy nut and canopy.
c. Unscrew bonnet assembly from valve body by hand. (If neces-
sary, use appropriate size wrench on outside diameter of bonnet.
However, this may cause damage and require replacement of the
bonnet assembly.)
d. Remove poppet/seal assembly from body.
2. Check Valve Removal
a. Evenly depress retaining bracket approximately 1/4", and rotate
bracket 90 degrees.
b. Remove the bracket, spring and check assembly.
3. Check Valve Seal Replacement
a. Remove screw holding the guide, and lift the seal from its holder.
CAUTION: Do not damage the guide legs or the guide pin of the
holder.
b. Insert seal disc into holder, position guide in center of seal and
thread the retaining screw through the guide into the holder.
c. Lightly tighten the screw to hold the guide from rotation.
CAUTION: Over-tightening may cause distortion of the guide legs.
4. Assembly
To reassemble the device use the reverse procedure described above
along with the following special instructions.
a. Position check assembly into valve body. Position spring into
recessed area on top side of check assembly. NOTE: In some cases
it may be easier to position the spring on the check assembly prior
to positioning in the valve body.
Typical Installations
Outside Installation (Side View)
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3
PRESSURE VACUUM BREAKER
B. Model 765 – 1 1/2" through 2" sizes
1. Disassembly
a. Close outlet ball valve then close inlet ball valve. Bleed residual pres-
sure by opening #2 testcock.
b. Remove the six bonnet bolts and lift the bonnet from valve body.
Remove poppet and remove seat disc.
c. To replace poppet spring: unscrew nut, unscrew guide pin and
remove spring. Use caution to avoid damage to guide pin. Install
new spring and reassemble.
d. Remove the spring retaining web, spring and check assembly.
2. Check Valve Seal Replacement
a. Remove guide retaining nut and guide, lift seal from holder.
b. Insert new seal, position guide in center of holder/seal and thread
nut to retain guide. Lightly tighten nut to hold the guide from rotat-
ing.
3. Assembly
a. Position the check valve assembly, spring and retaining web into
valve body. Ensure the arms of the retaining web are aligned with
the guide and supports in the valve body.
b. Roll rubber disc into recess on poppet and position poppet assembly
in the retaining web. Place the bonnet on the valve body. Ensure the
retaining web is properly supported by the three case bosses inside
the bonnet.
c. Insert the bonnet bolts and tighten.
d. Rapidly open inlet ball valve to minimize spillage in the air vent.
Slowly open outlet ball valve.
e. Test unit to ensure proper operation.
Pressure Vacuum Breaker – Model 765
"ONNET
!SSEMBLY
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/RING
3PRING
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7ASHER
3TEM
(OLDER
$ISC
'UIDE
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2UBBER$ISC
0OPPET
2ETAINER
3PRING
#HECK
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Fig. Description Quantity 765 765 765 765 765 765
No. 1
/
2" 3
/
4" 1" 11
/
4" 11
/
2" 2"
1 Nut 523-533-00 523-533-00 523-543-00 523-543-00 523-543-00 523-543-00
2 Canopy 300-092 300-093 300-089 300-089 300-083 300-083
4 Bolt 6 - - - - 1024564 1024564
6 O-Ring 1101068 1101068 398-140-72 398-140-72 398-247-72 398-247-72
7 Spring - - - - 630-096 630-096
10 Stem - - - - 200-767 200-767
13 Retainer 300-096 300-096 300-088 300-088 - -
14 Spring 630-108 630-108 630-106 630-106 630-063 630-063
20 Test Cock 2 781-074 781-074 781-075 781-075 781-075 781-075
22 Ball Valve 2 781-047 781-048 781-049 781-050 781-051 781-052
Part Kits
Rubber Parts Kit (6, 11, 16) 905-020 905-020 905-021 905-021 905-022 905-022
Bonnet Assembly (5-10) 905-047 905-047 905-048(2) 905-048(2) - -
Bonnet/Kit (3, 5-10) - - - - 901-857 901-857
Poppet Assembly (11,12) 905-049 905-049 905-050 905-050 901-860 901-860
Check Assembly (15-18) 905-051 905-051 905-052 905-052 - -
Check Repair Kit (6, 13, 15-18) - - - - 905-070 905-070
Bonnet/Poppet Kit (5-12) 905-211 905-211 905-212(2) 905-212(2) - -
(2) Kit includes parts to retrofit older style units
b. When installing the retaining bracket, ensure the spring is centered
around the base of the bracket.
c. Roll rubber disc into recess on poppet and position the poppet
assembly in the valve body.
d. To ease assembly of the bonnet into the valve body, apply a thin
coating of Vasoline on the o-ring. DO NOT USE ANY OTHER
LUBRICANT.
e. Ensure the guide pin of the bonnet correctly enters the hole in the
poppet.
f. Thread the bonnet into the valve body by hand until the bonnet
flange bottoms on top surface of valve body. DO NOT OVER-
TIGHTEN.
g. Tighten canopy nut only until canopy cannot turn freely.
h. Rapidly open inlet ball valve to minimize spillage through the air
vent. Slowly open outlet ball valve.
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PRESSURE VACUUM BREAKER
Symptom: Cause: Solution:
1. Check value fails to hold 1.0 A. Debris on sealing surface or guide surfaces Disassemble and clean check
psid minimum valve surfaces
B. Damaged seat disc Disassemble and replace seal
C. Weak or broken spring Disassemble and replace spring
D. Poppet broken due to thermal expansion Replace broken poppet (see freeze protection)
2. Poppet fails to open at 1.0 A. Debris restricting free operation Disassemble and clean check valve surfaces
psig minimum B. Poppet seal adhering to bonnet Disassemble and clean and/or replace damaged parts
C. Weak spring load Replace bonnet assembly (1
/
2- 11
/
4)
Replace spring (11
/
2and larger)
3. Minor leakage through air vent A. Damaged poppet seal Disassemble and replace seal
B. Cracked or damaged poppet Disassemble and replace poppet seal
C. Cracked bonnet or damaged sealing edge Disassemble and replace bonnet assembly
D. Debris on sealing surface Disassemble and clean
4. Significant discharge through A. Poppet not properly guided Disassemble and replace damaged parts
air vent B. Major poppet or seal failure Disassemble and replace damaged parts
C. Low downstream pressure Check pressure at #2 testcock; should
be higher than 5 psig if low system
D. Insufficient inlet volume to operate device Pressure needs to be increased or partially
closed outlet ball valve to create higher
pressure on poppet.
E. Poppet and or bonnet broken Replace broken bonnet/poppet
due to thermal expansion (see freeze protection)
5. Chatter during flow conditions A. Worn, damaged or defective check valve guide Disassemble and repair or replace guide
Troubleshooting Guide
A Division of Watts Water Technologies, Inc. USA: 4381 N. Brawley • Ste. 102 • Fresno, CA • 93722 • Tel. (559) 441-5300 • Fax: (559) 441-5301 • www.FEBCOonline.com
Canada: 5435 North Service Rd. • Burlington, ONT. • L7L 5H7 • Tel. (905) 332-4090 • Fax: (905) 332-7068 • www.FEBCOonline.ca
IOM-F-765 0823 © FEBCO, 2008
IOM-F-765.indd 4 8/11/08 2:56:43 PM
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