INST2018_Model350_65-250 Rev. 11/18
ZURN.COM.AU
ZURN WILKINS BACKFLOW
Double Check Valve Assembly
INSTALLATION & MAINTENANCE
MODEL 350 65-250mm
SERVICING CHECK VALVES
Attach a ratchet wrench, 17mm deep socket, and a 100mm
long extension are recommended for removing check
assemblies.
1.
Close inlet and outlet shut-off valves.
2.
Open No. 2, No. 3 and No. 4 test cocks to release pressure
from valve.
3.
Loosen & remove the grooved coupling around the access
cover. Remove cover.
4.
To service only the #1 check assembly, remove the 6 bolts,
washers and o-rings from the back of the #1 check assembly.
Separate the retainer and the seal ring from the check
assembly and proceed to step #8.
5.
To service both checks or the #2 check, the #1 check assembly
must first be removed. Remove the 4 nuts and washers
retaining the #1 check assembly. Remove the #1 check
assembly from the body.
6.
To remove the #2 check assembly, remove the 7 nuts,
washers and the #2 check retaining ring. Grasp the check
assembly by the stem and remove from valve.
7.
Remove all 6 bolts, washers and o-rings from the check
assembly (See “Check Assembly” illustration). Separate
retainer from check assembly to expose seal ring for inspec
-
tion.
8.
Inspect the rubber seal ring for cuts or embedded debris. If
the reverse side of the seal ring is unused, it is possible to
invert the seal ring. This would be considered a temporary
solution to fixing a fouled check and should be replaced with
a new seal ring as soon as possible.
9.
Inspect valve cavity and seating areas. Remove any debris.
10.
Reverse the above procedures to reinstall check assemblies.
Lubricate seat o-rings to hold them in place while reinstalling
seat. Place washers on studs and tighten retaining nuts
evenly.
11.
Reinstall access cover and grooved coupling.
NOTE:
If any portion of the seat assembly is damaged or missing or if
the seat sealing rib is damaged in any way, do not attempt to
field repair it. Contact your local ZURN WILKINS representa
-
tive for assistance.
CHECK ASSEMBLY
SEAT ASSEMBLY
SEAL RING
O-RING
(BOLT)
SEAL RETAINER
WASHER
BOLT
CHECK HANDLE
O-RING (SEAT)
65 & 80mm
100 & 150mm
SEAT ASSEMBLY
SEAL RING
O-RING
SEAL RETAINER
WASHER
NUT
O-RING (SEAT)
SEAT ASSEMBLY
SEAL RING
O-RING
(BOLT)
RETAINER
WASHER
BOLT
200 & 250mm
All Model 350 Double Check Valve Backflow Preventers must be
inspected and maintained by licensed personnel at least once a
year or more frequently as specified by local codes. Replace
-
ment of worn or damaged parts must only be made with
genuine “ZURN WILKINS” parts.
GENERAL MAINTENANCE
1.
Clean all parts thoroughly with water after disassembly.
2.
Carefully inspect rubber seal rings and o-rings for damage.
3.
Test unit after reassembly for proper operation (refer to
“TESTING PROCEDURES”).
