Troubleshooting Guide - Backflow Preventers
Problem Cause
Solution
A.
Valve spits periodically from the vent.
A.1
Fluctuating supply pressure.
A.2
Fluctuating downstream pressure.
B.
Valve drips continually from the vent
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 backpressure, freezing or water
hammer has distorted the second check.
B.5
Electrolysis of relief valve seat or first
check
seats.
B.6
Valve improperly reassembled.
C.
Valve exhibits high pressure drop.
C.1
Fouled strainer.
C.2
Valve too small for flows encountered.
D.
No water flow downstream of valve.
D.
Valve installed backwards.
E.
Valve does not test properly.
E.1
Follow manufacturer’s test procedure
E.2
Leaky downstream gate valve.
F.
Valve quickly and repeatedly fouls following
servicing.
F.
Debris in pipe line is too fine to be trapped
by strainer.
G.
Winterization of backflow preventers.
A.1
Install a soft seated check valve immediately
upstream of the device. (Watts
3
⁄
4
" - 2" (20-50mm)
No. 601 bronze valve.)
A.2
Install a soft seated check valve downstream of
the device close as possible to the shutoff valve.
(Watts
3
⁄
4
" - 2" (20-50mm) No. 601 bronze valve.)
B.1
Flush valve. If flushing does not resolve problem,
disassemble valve and clean or replace the
first check.
B.2
Clean or replace the relief valve seat.
B.3
Clean, grease or replace the piston O-ring.
B.4
Eliminate source of excessive backpressure or
water hammer in the system downstream of the
device. Use Watts No. 601 to dampen out back
pressure and No. 15 to eliminate water hammer.
Replace defective second check assembly. In
case of freezing; thaw, disassemble and inspect
internal components. Replace as necessary.
B.5
Replace relief valve seat or inlet cover. Install
dielectric unions (Watts Series 3001 through 3006).
Electrically ground the piping system and/or
electrically isolate the device with plastic pipe im-
mediately upstream and downstream of the device.
B.6
If valve is disassembled during installation, caution
must be exercised to install 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, 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
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, re-
moval of the complete body is the best. This
would create an air gap to eliminate any
possible backflow.
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