7
Troubleshooting - 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 de vice.
A.2
Fluctuating downstream pressure.
A.2
Install a soft seated check valve downstream of the
device as 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 re place the first check.
B.2
Damaged or fouled relief valve seat.
B.2
Clean or replace the relief valve seat.
B.3
Relief valve piston O-ring not free to
move due to pipe scale, dirt, or build
up of mineral deposits.
B.3
Clean, grease, or replace the piston O-ring.
B.4
Excessive back pressure, freezing,
or water hammer has distorted the
second check.
B.4
Elim i nate source of excessive back pressure or water
hammer in the system downstream of the device. Use
Watts No. 15 to eliminate water hammer. Replace
defective second check assembly.
In case of freezing, thaw, dis as sem ble, and inspect
internal components.
Replace as necessary.
B.5
Electrolysis or relief valve seat or first
check seats.
B.5
Replace relief valve seat or inlet cover.
Electrically ground the piping system and/or electri-
cally isolate the device with plastic pipe immediately
upstream and down stream of the device.
B.6
Valve improperly reassembled.
B.6
If the valve is dis as sem bled during installation, exercise
caution when installing 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 down-
stream of valve.
D.
Valve installed backward.
D.
Install valve in accordance with flow direction arrow.
E.
Valve does not
test properly.
E.1
Manufacturer's test procedure
not followed.
E.1
Clean or replace gate valve with full port ball valves or
resilient wedge shutoff valves.
E.2
Leaky downstream gate valve.
E.2
Clean or replace gate valve with full port ball valves or
resilient wedge shutoff valves.
F.
Valve quickly and
repeatedly fouls
following servicing.
F.
Debris in pipeline is too fine to be
trapped by strainer.
F.
Install finer mesh strainer element in the strainer.
G.
Performance of
backflow preventers
affected during winter
season.
G.
Cold temperatures.
G.
Electric heat-tape wrap closely together around the
valve body. Build a small shelter around the valve
with a large light bulb installed and left on at all times.
If the supply line is not used during the winter, removal
of the com plete body is the best. This would create
an air gap to eliminate any possible backflow.
