Watts 909 Serie Manual De Instalación & Mantenimiento página 7

Troubleshooting - Backflow Preventers
Problem
A. Valve spits periodically
from the vent.
B. Valve drips continually
from the vent.
C. Valve exhibits high
pressure drop.
D. No water flows down-
stream of valve.
E. Valve does not
test properly.
F. Valve quickly and
repeatedly fouls
following servicing.
G. Performance of
backflow preventers
affected during winter
season.
Cause
A.1 Fluctuating supply pressure.
A.2 Fluctuating downstream pressure.
B.1 Fouled first check.
B.2 Damaged or fouled 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.4 Excessive back pressure, freezing,
or water hammer has distorted the
second check.
B.5 Electrolysis or relief valve seat or first
check seats.
B.6 Valve improperly reassembled.
C.1 Fouled strainer.
C.2 Valve too small for flows encountered.
D. Valve installed backward.
E.1 Manufacturer's test procedure
not followed.
E.2 Leaky downstream gate valve.
F. Debris in pipeline is too fine to be
trapped by strainer.
G. Cold temperatures.
Solution
A.1 Install a soft seated check valve immediately upstream
of the de vice.
A.2 Install a soft seated check valve downstream of the
device as close as possible to the shutoff valve.
B.1 Flush valve. If flushing does not resolve problem,
disassemble valve and clean or re place the first check.
B.2 Clean or replace the relief valve seat.
B.3 Clean, grease, or replace the piston O-ring.
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 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 If the valve is dis as sem bled during installation, exercise
caution when installing check springs in their proper
location.
C.1 Clean strainer element or replace.
C.2 Install proper size device based upon
flow requirements.
D. Install valve in accordance with flow direction arrow.
E.1 Clean or replace gate valve with full port ball valves or
resilient wedge shutoff valves.
E.2 Clean or replace gate valve with full port ball valves or
resilient wedge shutoff valves.
F. Install finer mesh strainer element in the strainer.
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.
7