Manual

All Model 975XL Reduced Pressure Principle and Model 950XL Double
Check Valve Backflow Preventers must be inspected and maintained
by licensed personnel at least once a year or more frequently as speci-
fied by local codes. Replacement of worn or damaged parts must only
be made with genuine "WILKINS" parts. The WILKINS Certificate of
Limited Warranty provides that failure to do so "...releases WILKINS of
any liability that it might otherwise have with respect to that device."
Such failure could also result in an improperly functioning device.
The Model 975XL Reduced Pressure Principle Assemblies should be
thoroughly flushed after backflow conditions occur to prevent any type
of corrosive deterioration to its components. Failure to do so could re-
sult in malfunction of the device.
GENERAL MAINTENANCE
1. Clean all parts thoroughly with water after disassembly.
2. Carefully inspect rubber seal rings, diaphragms and o-rings for
damage.
3. Test unit after reassembly for proper operation(see "Testing
Procedures").
SERVICING CHECK VALVES
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. Unscrew check valve covers using appropriate size wrench (CAU-
TION: Cover is spring loaded). To avoid injury, hold cover down firmly
with one hand while unscrewing.
4. Remove check valve cover, spring and poppet assembly.
3
Maintenance Instructions
When the relief valve discharges intermittently it can be almost always assumed that the device is functioning correctly and that the discharge is
caused by systems such as inlet pressure fluctuations or water hammer due to quick closing valves.
PROBLEM CORRECTIVE ACTION
1. SUDDEN OR RAPID SPITTING
POSSIBLE CAUSES
1. Drop in inlet pressure.
2. Sudden increase in downstream pressure
due to waterhamnmer from quick closing
shut-off valve installed downstream.
A. Install an in-line spring loaded check valve
upstream of backflow.
B. Install pressure reducing valve upstream of
backflow unit.
C. Install in-line spring loaded check valve
downstream of backflow as close to source
as possible, but not closer that 4 feet.
2. LIGHT INTERMITTENT DRIP 1. Slightly fouled #1 check. A. Clean #1 check and turn check valve seal
ring over or replace.
Continuous discharge of the relief valve signifies a failure of some part of the device. To help determine the specific area of failure, close the #2 shut-
off valve. If the discharge stops, the #2 check requires service. If the discharge continues, the #1 check requires service.
1. CONTINUOUS DISCHARGE 1. Fouled #1 check.
2. Fouled relief valve seat.
3. Fouled #2 check.
A. Clean check valves and turn check valve
seal rings over or replace.
B. Clean relief valve seat and turn relief valve
seal ring over or replace.
In summation, the amount of discharge is proportional to degree of fouling. Most problems occur in the #1 check which is where debris enters the
backflow preventer first.
Troubleshooting
5. Inspect the rubber seal ring for cuts or embedded debris. To remove
seal ring, remove screw and seal ring retainer. 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.
6. Inspect valve cavity and seating area. Remove any debris.
7. If installed with removable seat, unscrew seat from body and re-
place with new seat and lightly grease o-ring.*
8. Reverse the above procedures to reinstall check valve assembly.
Care should be taken to make sure the heavy spring is installed in
the No. 1 check valve (Model 975's series only). For the 3/4"-1"
975XLSE the No. 2 poppet has a cupped seal retainer. For the
1 1/4"-2" 975XLSE the No. 1 seat has a taller seat profile than the
No. 2 seat.
SERVICING RELIEF VALVE
1. Remove relief valve cover bolts and cover. Gently pull on diaphragm
to remove the cartridge assembly.
2. Inspect seal ring for cuts and embedded debris. Turn over or replace
if required.
3. Disassemble cartridge by unscrewing relief valve retaining screw.
4. Inspect diaphragm and o-rings for damage. Replace required parts
and apply a light coat of grease to plunger o-ring.
5. Carefully reassemble cartridge assembly.
6. Inspect relief valve seat for wear on seating surface. If damaged,
replace seat and seat o-ring.*
7. Insert cartridge assembly into relief valve body.
8. Replace relief valve cover and cover bolts.
9. Place device in service and test per "TESTING PROCEDURES".
*For seat removal assistance, consult factory.
SPRING(CHECK)
O-RING(COVER)
COVER(CHECK)
POPPET
SEAL RING
(CHECK)
SEAL RING RETAINER
(CHECK)
RETAINING SCREW
(CHECK)
SEAT(CHECK)
O-RING(CHECK
SEAT)
O-RING(PLUNGER)
RELIEF VALVE COVER
COVER BOLTS
PLUNGER(UPPER)
DIAPHRAGM
PLUNGER(LOWER)
SEAL RING
(RELIEF VALVE)
SEAL RING RETAINER
(RELIEF VALVE)
SPRING
(RELIEF VALVE)
RETAINING SCREW
(RELIEF VALVE)
SEAT O-RING
(RELIEF VALVE)
SEAT(RELIEF VALVE)