Model 350

Double Check Valve Assembly (3/4”& 1”)



Installation  Testing  Maintenance Instructions

INSTALLATION INSTRUCTIONS PLACING THE MODEL 350 IN SERVICE

®

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 device.

ZURN WILKINS Model 350 Double Check Valve assemblies are for use on 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 expansion could create excessive line pressure. Where this could occur, shock arresters, 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. 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 350 Double Check Valve assembly is now in service.

1. Before installing a Model 350 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.

4. After the Model 350 has been properly installed, test the device (see “TEST PRO-

CEDURES”). 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.

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.

WILKINS 350

DIRECTION OF FLOW

OPTIONAL STRAINER

(MODEL SXL)

PROTECTIVE

ENCLOSURE

WILKINS 350

12" MIN.

30" MAX.

WILKINS 350

DIRECTION OF FLOW

VERTICAL INSTALLATION INDOOR INSTALLATION

DIRECTION OF FLOW

OUTDOOR INSTALLATION

Vertical installation is acceptable in applications where inlet and outlet piping are flowing vertically upwards. All the basic installation instructions apply to such installations.

Consult factory for approval status.

Indoor installation is preferred in areas that are subject to freezing conditions. All the basic installation instructions apply to such installations.

The Model 350 Backflow Preventer may be installed outdoors only if the device is protected against freezing conditions.

Exposure to freezing conditions will result in improper function or damage to the device. The installation location must be kept above 32°F. All the basic installation instructions apply.

Proposition 65 Warning This product contains chemicals known to the State of California to cause cancer or birth defects or other reproductive harm.

In accordance with U.S. Federal Safe Drinking Water Act Lead-Free requirements, as of January 4, 2014, this product can only be used in water systems considered non-potable. Please contact your local water utility for further requirements.

Testing Procedures

MODEL 350 DOUBLE CHECK VALVE ASSEMBLY

Equipment Required: Differential pressure gauge test kit.

TEST NO. 1 - TIGHTNESS OF #1 CHECK VALVE

REQUIREMENT:

The static pressure drop across check valve #1 shall be at least

1.0 psid. If test cock #3 is not at the highest point of the check valve body, then a vertical tube must be installed on test cock #3 so that it rises to the top of the check valve body.

PROCEDURE:

1. Slowly open all 4 test cocks to remove any foreign material

and attach fittings.

2. Attach hose from the high side of the test kit to the #2 test cock.

3. Open test cock #2 and bleed all air from the hose and gauge

by opening the high side bleed needle valve. Close high side

bleed needle valve. If a tube is attached to test cock #3, open

test cock #3 to fill the tube. Close test cock #3. Close #2

shut-off valve then close the #1 shut-off valve.

4. Hold gauge at same level as test cock #3 or water level in

tube. Slowly open test cock #3. Record the static pressure drop

across check valve #1 after gauge reading stabilizes and

water stops running out of test cock #3.

5. Close all test cocks, open shut-off valve #1 and remove test

equipment.

TEST NO. 2 - TIGHTNESS OF #2 CHECK VALVE

REQUIREMENT:

The static pressure drop across check valve #2 shall be at least

1.0 psid. If test cock #4 is not at the highest point of the check valve body, then a vertical tube must be installed on test cock #4 so that it rises to the top of the check valve body.

PROCEDURE:

1. Attach hose from the high side of the test kit to the #3 test cock.

2. Open test cock #3 and bleed all air from the hose and gauge

by opening the high side bleed needle valve. Close high side

bleed needle valve. If a tube is attached to test cock #4,

open test cock #4 to fill the tube. Close test cock #4.

Close #1 shut-off valve.

3. Hold gauge at same level as test cock #4 or water level

in tube. Slowly open test cock #4. Record the static pressure

drop across check valve #2 after gauge reading stabilizes

and water stops running out of test cock #4.

4. Close all test cocks, slowly open shut-off valve #1 & #2 and

remove test equipment.

#2 TEST COCK

#1 TEST COCK

#3 TEST COCK

#4 TEST COCK

#1 SHUT-OFF

VALVE

LOW SIDE BLEED

NEEDLE VALVE

WILKINS 350

HIGH SIDE BLEED

NEEDLE VALVE

#2 SHUT-OFF

VALVE

LOW SIDE HOSE HIGH SIDE HOSE

VENT HOSE

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ZURN WILKINS

1747 Commerce Way, Paso Robles, CA 93446 Phone:855-663-9876 Fax:805-238-5766 www.zurn.com

®

Maintenance Instructions

Seat

Poppet

Spring

Tailpiece

CHECK ASSEMBLY

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. 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”).

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 the 4 bolts (1/4-20 UNC Hex Flange) holding the

housing in place.

4. Using a #2 flathead screwdriver, pry loose housing by plac-

ing the screwdriver in the notch between housing and body.

5. Pull housing out of the body and remove checks by sliding

them towards the outlet of housing.

6. Using the same screwdriver, locate the notch between seat

and tailpiece of each check. Insert screwdriver and twist to

“snap” checks apart. CAUTION: Checks are spring loaded.

7. Inspect the rubber seal ring around poppet for cuts or

embedded debris.

8. If the poppet is damaged, replace with a new poppet.

9. Inspect the remaining check parts and seating areas. Re-

move any debris.

10. If necessary, replace any damaged parts with new ones.

11. Lightly grease o-rings on checks and reinstall into housing

following the above procedures in reverse order.

12. Flush body prior to reinstalling housing.

13. Lightly grease o-rings on housing and reinstall into body

following the above procedures in reverse order.

Note: When installing housing, match slight taper on the outlet of the housing with corresponding taper in body.

Hex Flange Bolts

No. 3

Test Cock

No. 1

Test Cock

Inlet

O-ring

No. 2

Test Cock

Outlet

O-ring

Inlet

Ball Valve

No. 4

Test Cock

Housing

Body

Outlet

Ball Valve

FIGURE 1

®

#1 Check

O-ring

#1 Check

Assembly

#2 Check

O-ring

#1 Seat

Poppet

Spring

Tailpiece

#2 Seat

#2 Check

Assembly

FIGURE 2 FIGURE 3

ZURN WILKINS

1747 Commerce Way, Paso Robles, CA 93446 Phone:855-663-9876 Fax:805-238-5766 www.zurn.com

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Troubleshooting

PROBLEM

1. LEAKING CHECK VALVES

POSSIBLE CAUSES

1. Debris on seat or seal ring

2. Damaged seat

3. Damaged seal ring

4. Damaged check o-ring

2. LOW OR NO FLOW 1. Device installed backwards

2. Shut-off valves or valve upstream

may not be fully open

3. Low supply pressure

Performance Characteristics

15

0.00

10

5

0

0

1.26

FLOW CHARACTERISTICS

MODEL 350 3/4" & 1" (STANDARD & METRIC)

FLOW RATES (l/s)

2.52

3.79

3/4" (20mm)

20 40

FLOW RATES (GPM)

60

CORRECTIVE ACTION

1. Clean seat and seal ring area

2. Replace seat

3. Replace poppet

4. Replace check o-ring

1" (25mm)

5.05

103

80

0

69

34

Capacity thru Schedule 40 Pipe

Pipe size 5 ft/sec 7.5 ft/sec 10 ft/sec 15 ft/sec

1/8"

1/4"

3/8"

1/2"

1

2

3

5

1

2

4

7

2

3

6

9

3

5

9

14

3/4"

1"

1 1/4"

1 1/2"

2"

8

13

23

32

52

12

20

35

48

78

17

27

47

63

105

25

40

70

95

167

SPECIFICATIONS

Maximum working water pressure 175 PSI

Maximum working water temperature 180°F

Hydrostatic test pressure

End connections

350 PSI

Threaded ANSI B1.20.1

Proper performance is dependent upon licensed, qualified personnel performing regular, periodic testing according to ZURN

WILKINS’ specifications and prevailing governmental & industry standards and codes and upon following these installation instructions. Failure to do so releases ZURN WILKINS of any liability that it might otherwise have with respect to that device. Such failure could also result in an improperly functioning device.

®

IS350-34-1 (REV. 4/13)

ZURN WILKINS

1747 Commerce Way, Paso Robles, CA 93446 Phone:855-663-9876 Fax:805-238-5766 www.zurn.com

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