Manual

Model 950XL
Double Check Valve Assembly (3/4"-2")
CAUTION: Installation of Backflow Preventers
must be performed by qualified, licensed per-
sonnel. The installer should be sure the proper
device has been selected for the particular in-
stallation. Faulty installation could result in an
improperly functioning device.
WILKINS Model 975XL Reduced Pressure
Principle Backflow Preventers are for use on
potable water lines where a health hazard could
exist if a backflow situation were to occur.
WILKINS Model 950XL Double Check Valve
assemblies are for use on potable water lines
where a health hazard does not exist in the
event of a backflow situation.
Proper performance is dependent upon follow-
ing these installation instructions and prevail-
ing governmental and industry standards and
codes. Failure to do so, according to WILKINS
Limited Warranty "...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.
Damage to the device could result wherever
water hammer and/or water thermal expansion
could create excessive line pressure. Where
this could occur, shock arresters and/or pres-
sure relief valves should be installed down-
stream of the device.
1. Before installing either a Model 975XL or
Model 950XL Backflow Preventer, flush the line
thoroughly to remove all debris, chips and other
foreign matter. If required, a strainer should be
placed upstream of the Backflow Preventer.
CAUTION: Do not use a strainer in seldom used
emergency waterlines such as fire lines.
2. The Model 975XL must be installed in a hori-
zontal position to provide proper operation of
the relief valve.
3. Provide adequate space around the installed
unit so that the test cocks will be accessible for
testing and servicing.
4. If installation of a Model 975XL is in a build-
ing, provide a suitable drain arrangement to
drain off spillage from the relief valve. An air
gap at least two times the pipe diameter must
be provided between the relief valve and the
drain piping to prevent a cross-connection.
PLACING THE DEVICE IN SERVICE
After the installation of a Model 975XL or Model
950XL has been completed, place the unit in
service as follows:
OUTDOOR INSTALLATION
Model 975XL and Model 950XL Backflow
Preventers may be installed outdoors only if
the device is protected against freezing condi-
tions. Exposure to freezing conditions will re-
sult in improper function or damage to the de-
vice. The installation location must be kept
above 32°F. All the basic installation instructions
apply.
If installation is in a pit or vault, the Backflow
Preventer must never be submerged in water
because this could cause a cross-connection.
Make sure that the pit or vault always remains
dry by providing ample drainage.
INDOOR INSTALLATION
Indoor installation is preferred in areas that are
subject to freezing conditions. All the basic in-
stallation instructions apply to such installations.
PARALLEL INSTALLATION
Where uninterrupted service from a single
meter connection must be maintained, two or
more Backflow Preventers may be connected
in parallel. All the basic installation instructions
apply to parallel installation. Be sure to allow
adequate room between the units for testing
and repair.
CAUTION: Do not pipe the relief valve solidly
to a floor drain, sewer or sump.
5. Install valve at least 12 inches above sur-
rounding flood level.
6. Always consult local codes for installation
methods, approvals and guidance.
975XL REDUCED PRESSURE PRINCIPLE
1. Start with both shut-off valves closed. Slowly
open the inlet shut-off valve until the backflow
preventer is completely pressurized. A brief dis-
charge from the relief valve may occur while
the device is pressurizing. The discharge should
cease by the time the shut-off valve is fully open.
Device should function properly. If the discharge
does not stop, refer to "MAINTENANCE IN-
STRUCTIONS" for repair procedures.
2. After the device has been pressurized, vent
all trapped air from both check valve by slightly
opening each of the four test cocks.
3. Slowly open the downstream shut-off valve.
The Model 975XL Reduced Pressure Principle
Backflow Preventer is now in service.
4. If "spitting" or intermittent discharges from
the relief valve are noted, it could be a result of
pressure fluctuation and/or a water hammer
condition in the system. If such conditions ex-
ist, install water pressure reducing valves or
water hammer shock arresters in compliance
with industry standards as needed.
5. After the Model 975XL has been properly
installed, test the device (see "TEST PROCE-
DURES"). If the device fails the test, remove
the first and second check valves and thor-
oughly flush the device. If the relief valve fails to
operate properly, inspect the sensing passage
for clogging (see "MAINTENANCE INSTRUC-
TIONS"). Clean rubber seals of all debris and
place unit back in service.
950XL DOUBLE CHECK VALVE ASSEMBLY
1. Start with both shut-off valves closed. Slowly
open the inlet shut-off valve until the backflow
preventer is completely pressurized.
2. When the unit has been pressurized, vent
any trapped air by slightly opening each of the
four test cocks.
3. Slowly open the downstream shut-off valve.
The Model 950XL Double Check Valve assem-
bly is now in service.
4. After the Model 950XL has been properly
installed, test the device (see "TEST PROCE-
DURES"). If the device fails the test, remove
the first and second check valves and thor-
oughly flush the device. Clean rubber seats of
all debris and place unit back in service.
12" MIN
30" MAX
PROTECTIVE
ENCLOSURE
OPTIONAL
WATER METER
INLET SHUT-OFF
AIR GAP
DRAIN
DIRECTION OF FLOW
Model 975XL
Reduced Pressure Principle Assembly (1/4"-2")
q Installation q Testing q Maintenance Instructions
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Proposition 65 Warning This product contains chemicals known to the State of California to cause cancer or birth defects or
other reproductive harm.