#1 CHECK ASSEMBLY
#2 PLATE RETAINER
#2 CHECK ASSEMBLY
GASKET
#1 RETAINER
Maintenance Instructions
3
FIGURE 1
FIGURE 2
FIGURE 3
Troubleshooting
All Model 350AST Series Backflow Preventers must be inspected
and maintained by licensed personnel at least once a year or
more frequently as specified by local codes. Replacement 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”).
NOTE:
If any portion of the seat assembly is damaged or
missing or if the seating surface is damaged in any way, do not
attempt to field repair it. Contact your local ZURN WILKINS
representative for assistance.
SERVICING CHECK VALVES
1. Close the outlet and then the inlet shut-off valves.
2. Open No. 2, 3 and 4 test cocks to release internal pressure.
Leave them open during check removal and reinstallation.
3. Loosen and remove the two nuts, bolts and gasket from the
grooved coupling around the access cover.
4. If the valve has a plastic retainer on the #1 check, grasp one
of the exposed ends, push down and then pull toward the #2
check. The retainer should “spiral” out of the groove around
the check.
the #2 check by locating one of the two spring-loaded
around the face of the check. Pinch the sides of
together and rotate the plates out of the body groove
nd
retainer the same way.
Start by removing the hardware and o-rings from the back
check assembly (See “Check Assembly” illustration). Sepa
-
g.
the seal ring for cuts or embedded debris. If the re
-
side of the seal is unused, the seal ring can be inverted
temporarily until a new seal is obtained. Inspect seat
.
valve cavity and seating areas. Flush with water to
, Lubricate the #2 check o-ring, install in the body and
#4 test cock. Install the #2 check retainers into the body
one plate at a time, squeezing the spring ends together to
and install the #1 check. Close the #2 test cock.
the plastic retainer by inserting one end into the body
and then sliding your hand around the face of the retainer,
it into the groove as you go. The retainer will "snap" into
e the outside surface of the grooved coupling gasket.
access cover and grooved coupling, making sure the
the coupling touch each other. Close any remaining open
PROBLEM
POSSIBLE CAUSES
CORRECTIVE ACTION
1. LEAKING CHECK VALVES
1. Debris on seat or seal ring
1. Clean seat area
2. Damaged seat area
2. Replace check assembly
3. Damaged seat o-ring
2. Replace seat o-ring
4. Damaged bolt o-ring (s) on check retainer
4. Replace o-ring (s)
2. LOW OR NO FLOW
1. Device installed backwards
1. Verify flow direction arrow
2. Gate valves not fully open
2. Turn handles counterclockwise
3. Low supply pressure
3. Attach pressure gauge to test cock #1 and verify pressure
ZURN WILKINS
1747 Commerce Way, Paso Robles, CA 93446 Phone:855-663-9876 Fax:805-238-5766
www.zurn.com
®
5. Remove the #2 check by locating one of the two spring-loaded
plate retainers around the face of the check. Pinch the sides of
the spring together and rotate the plates out of the body groove
one at a time. Remove the 2nd retainer the same way.
6. Always service the checks one at a time to avoid mixing
parts.
Start by removing the hardware and o-rings from
the back of the check assembly (See “Check Assembly”
illustration). Separate the seal retainer from the assembly to
expose the seal ring.
7. Inspect the seal ring for cuts or embedded debris. If the re
-
verse side of the seal is unused, the seal ring can be inverted
and used temporarily until a new seal is obtained. Inspect
seat o-ring and replace if cut or damaged in any way.
8. Inspect valve cavity and seating areas. Flush with water to
remove any debris.
9. Reassembly, Lubricate the #2 check o-ring, install in the body
and close the #4 test cock. Install the #2 check retainers into
the body groove one plate at a time, squeezing the spring
ends together to clear the stops on the face of the seat.
10. Lubricate and install the #1 check. Close the #2 test cock.
Install the plastic retainer by inserting one end into the body
groove and then sliding your hand around the face of the
retainer, pushing it into the groove as you go. The retainer
will "snap" into place when fully seated.
11. Lubricate the outside surface of the grooved coupling
gasket. Reassemble access cover and grooved coupling,
making sure the ends of the coupling touch each other.
Close any remaining open test cocks and place valve back
in service.
