Annual Inspection
Annual inspection of all water system safety and control valves
is required and necessary. Regular inspection, testing, and
cleaning assures maximum life and proper product function.
NOTICE
Shutoff Valves:
When shutoff valves are removed and reassem-
bly is necessary, the shutoff valve with the test cock is to be
mounted on the inlet side of the backflow preventer.
A. The assembly should always be installed in an accessible location
to facilitate testing and servicing.
Check the state and local
codes to ensure that the backflow preventer is installed in
compliance, such as the proper height above the ground.
B. Watts recommends that a strainer be installed ahead of the
assembly to protect the internal components from unnecessary
fouling.
CAUTION
!
Do not add a strainer when the backflow preventer is installed on
seldom-used water lines, such as fire sprinkler lines or other lines
called upon only during emergencies.
Start Up:
The downstream shutoff should be closed. Open the
upstream shutoff slowly and fill the valve. When the valve is filled,
open the downstream shutoff slowly and fill the water supply
system. This is necessary to avoid water hammer or shock
damage.
C. Water discharge from the relief valve should be vented in accor-
dance with code requirements. The relief valve should never be
solidly piped into a drainage ditch, sewer, or sump. The discharge
should be terminated approximately 12" above the ground or
through an air gap piped to a floor drain.
NOTICE
Relief Valve Discharge Rates
The installation of an air gap with the drain line terminating above
a floor drain handles any normal discharge or nuisance spitting
through the relief valve. However, floor drain size may need to be
designed to prevent water damage caused by a catastrophic
failure condition. See Figure 4 for maximum relief valve discharge
rates, size, and capacity of typical floor drains.
Do not
reduce the size of the drain line from the air gap fitting.
Pipe full line size.
D. After initial installation, a discharge from the relief valve opening
may occur due to inadequate initial flushing of pipe lines to
eliminate dirt and pipe compounds. If flushing does not clear,
remove the first check valve and clean thoroughly.
NOTICE
Periodic relief valve discharge may occur on dead end service
applications, such as boiler feed lines or cooling tower makeup
lines due to fluctuating supply pressure during a static or no flow
condition. To avoid this discharge, install a spring-loaded rubber
seated check valve ahead of the backflow assembly to “lock-in
”
the downstream pressure.
E. Backflow preventers should never be placed in pits unless abso-
lutely necessary and then only when and as approved by local
codes. In such cases, provision should be made to always vent
above flood level or for a pit drain to ensure an adequate air gap
below the relief port.
F. The backflow preventers must be inspected periodically for any
discharge from the relief valve which provides a visual indication
of need for cleaning or repair of check valves. Also testing for
proper operation of the device should be made periodically in
compliance with local codes, but at least once a year or more
often, depending upon system
conditions.
The relief vent discharges water when, during no-flow periods,
the first check valve is fouled or the inlet pressure to the device
drops sufficiently due to upstream pressure fluctuations to affect
the required operating differential between the inlet pressure and
reduced pressure zone. Otherwise, such relief (spitting) can
occur when the second check is fouled during emergency
backflow or resulting from a water hammer condition. (For more
information, download Troubleshooting Guide S-TSG at
NOTICE
Special considerations are necessary when testing assem
blies installed on Fire Prevention Systems.
Fire Protection System Installations:
The National Fire
Protection Agency (NFPA) Guidelines require a confirming flow
test be conducted whenever a “main line
”
valve such as a back-
flow assembly or the shutoff valves have been operated. Certified
testers of backflow assemblies must conduct this confirming test.
Figure 4
Relief Valve Discharge Rates
1
⁄
2
" – 1"
45
40
35
30
25
20
15
10
5
0
0 10 20 30 40 50 60 70 80 90 100 150
Zone Pressure psi
Flow Rate gpm
1
⁄
2
"
3
⁄
4
" M2
1" M2
X
1
1
⁄
4
" – 3"
350
300
250
200
150
100
50
0
0 10 20 30 40 50 60 70 80 90 100 150
Zone Pressure psi
Flow Rate gpm
2
1
⁄
2
"
– 3"
2" M2
1
1
⁄
4
" – 1
1
⁄
2
" M2
TYPICAL FLOW RATES AS SIZED BY FLOOR DRAIN MANUFACTURERS
2" 55 gpm
5" 350 gpm
3" 112 gpm
6" 450 gpm
4" 170 gpm
8" 760 gpm
3
