Model 950LF
INSTALLATION INSTRUCTIONS
Dual Check Backflow Preventer
(3/4", 1", 1 1/4", 1 1/2" & 2")
WARNING: This product contains lead. A chemical known to the State of California to cause cancer or birth defects or other
reproductive harm. Attention plumber/installer: California law requires that this warning be given to the consumer.
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Installation
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Testing
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Maintenance Instructions
CAUTION: Installation of backflow preventers must be performed by qualified, licensed
personnel. The installer should be sure the proper device has been selected for the
particular installation. Faulty installation could result in an improperly functioning de-
vice.
WILKINS Model 950LF dual check valve assemblies are for use on potable water
lines where a health hazard does not exist in the event of a backflow situation.
Damage to the device could result wherever water hammer and/or water thermal ex-
pansion could create excessive line pressure. Where this could occur, shock arres-
tors, check valves and/or pressure relief valves should be installed downstream of the
device.
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.
1. Before installing a Model 950LF 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 sel-
dom used emergency waterlines such as fire lines.
2. Provide adequate space around the installed unit so that the test cocks will be
accessible for testing and servicing.
3. Install valve at least 12 inches above surrounding flood level.
4. Always consult local codes for installation methods, approvals and guidance.
1. Start with the water service shut-off
valve in the closed position. 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 three test cocks.
3. After the Model 950LF has been prop-
erly installed, test the device (see "TEST
PROCEDURES"). If the device fails the
test, remove the first and second check
valves and thoroughly flush the device.
Clean rubber and seats of all debris and
place unit back in service.
PLACING THE 950LF IN SERVICE
1. Clean all parts thoroughly with water
after disassembly.
2. Carefully inspect rubber seal rings & o-
rings for damage.
3. Test device after reassembly for proper
operation
MAINTENANCE INSTRUCTIONS
1. The water service shut-off valve must
be turned to the open position. A down-
stream shut-off valve should be closed to
insure no water is flowing through the de-
vice.
2. Connect the high side hose of differen-
tial pressure gauge the #1 test cock. Con-
nect the low side hose of the differential pres-
sure gauge to the #2 test cock. Open test
cocks #1 & #2. Bleed gauge of air and ob-
serve differential reading. If gauge reads
1 psi or above, the check is considered
good. Close test cocks and remove hoses.
3. Attach low side hose to test cock #3 and
the high side hose to test cock #2. Open
test cocks #2 & #3. Bleed gauge of air and
observed differential reading. If gauge reads
1 psi or above, the check is considered good.
4. Close the test cocks and disconnect the
differential pressure gauge. The device is
now ready for operation.
TEST PROCEDURES
MODEL 950LF
WATER
METER
DIRECTION OF FLOW
INLET SUPPLY
SHUT-OFF
VENT HOSE
LOW SIDE HOSE
HIGH SIDE HOSE
LOW SIDE BLEED
NEEDLE VALVE
#3 TEST COCK
#2 TEST COCK
#1 TEST COCK
HIGH SIDE BLEED
NEEDLE VALVE
The Model 950LF Backflow Preventer may
be installed outdoors only if the device is pro-
tected against freezing conditions. Exposure
to freezing conditions will result in improper
function or damage to the device. The in-
stallation location must be kept above 32°F.
All the basic installation instructions apply.
OUTDOOR INSTALLATION
INDOOR INSTALLATION
Vertical installation is acceptable in applica-
tions where inlet and outlet piping are flow-
ing vertically upwards. All the basic installa-
tion instructions apply to such installations.
Consult factory for approval status.
VERTICAL INSTALLATION
Indoor installation is preferred in areas that
are subject to freezing conditions. All the
basic installation instructions apply to such
installations.
