Troubleshooting Guide - Backflow Preventers
Problem
Cause
Solution
A.
Valve spits periodically from the vent
A.1
Fluctuating supply pressure.
A.1
Install a soft seated check valve immediately
upstream of the device.
A.2
Fluctuating downstream pressure
A.2
Install a soft seated check valve downstream of
the device close as possible to the shutoff valve.
B.
Valve drips continually from the vent
B.1
Fouled first check
B.1
Flush valve. If flushing does not resolve problem,
disassemble valve and clean or replace the first
check.
B.2
Damage or fouled relief valve seat.
B.2
Clean or replace the relief valve seat.
B.3
Relief valve piston O-ring not free to
B.3
Clean, grease or replace the piston O-ring.
move due to pipe scale, dirt or build
up of mineral deposits.
B.4
Excessive back pressure, freezing, or
B.4
Eliminate source of excessive backpressure or
water hammer has distorted the
water hammer in the system downstream of the
second check.
device. Use Watts No. 15 to eliminate water ham-
mer. Replace defective second check assembly.
In case of freezing; thaw, disassemble and inspect
internal components.
Replace as necessary.
B.5
Electrolysis or relief valve seat or first
B.5
Replace relief valve seat or inlet cover.
check seats.
Electrically ground the piping system and/
or electrically isolate the device with plastic pipe
immediately upstream and downstream of
the device.
B.6
Valve improperly reassembled.
B.6
If valve is disassembled during installation,
caution must be exercised to install check springs
in their proper location.
C.
Valve exhibits high pressure drop.
C.1
Fouled strainer.
C.1
Clean strainer element or replace.
C.2
Valve too small for flows encountered.
C.2
Install proper size device based upon
flow requirements.
D.
No water flows downstream of valve.
D.
Valve installed backwards.
D.
Install valve in accordance with flow
direction arrow.
E.
Valve does not test properly
E.1
Follow manufacturer's test procedure
E.1, E.2
Clean or replace gate valve with full port ball
valves or resilient wedge shutoff valves.
E.2
Leaky downstream gate valve.
F.
Valve quickly and repeatedly fouls following servicing.
F.
Install finer mesh strainer element in the strainer.
F.
Debris in pipe line is too fine to be
trapped by strainer.
G.
Winterization of backflow preventers.
G.
Electric heat-tape wrap closely together around
valve body. Build a small shelter around the valve
with a large light bulb installed and left on at all times.
If supply line is not used during the winter, removal
of the complete body is the best. This would create
an air gap to eliminate any possible backflow.
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