Watts LF919 - Manual (Page 3)

3
WARNING:
Do not allow the drain line to empty directly into a drainage ditch, sewer system, or sump.
NOTE: Relief Valve Discharge Rates
The Series 919 and LF919 air gap and drain line terminating above a floor drain
can accommodate any moderate discharge or nuisance spitting through the
relief valve. However, to prevent water damage in the case of a catastrophic fail-
ure, you may need to design the floor drain size to accommodate the increased
discharge. Refer to Figure 1 for maximum relief valve discharge rates, size, and
capacity of typical floor drains.
NOTE: DO NOT reduce the size of the drain line from the air gap fitting. The drain
line must remain at full line size.
E. After initial installation of the Series 919 and LF919, a discharge from the relief
valve may occur due to dirt and pipe compounds. This may be due to inad-
equate initial flushing of the pipe lines. If flushing the valve does not clear the
unit, remove the first check valve and clean thoroughly, using the procedures
in "Servicing First & Second Check Valves" on page 6.
NOTE: Periodic relief valve discharge may occur on dead end service applications,
such as boiler feed lines or cooling tower makeup lines. This may be 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.
F. It is recommended that you not place the Series 919 and LF919 in a pit or at
a depth below the ground level, unless absolutely necessary. If an installation
requires below ground level installation, a modified pit installation is recom-
mended, as well as the approval of local codes. In such cases, provision
should be made to always vent the drain line above the flood level. In the
case of a pit drain, ensure an adequate air gap exists between the bottom of
the drain line and the bottom of the pit.
G. It is recommended that periodic inspection of the Series 919 and LF919 be
done to check for any discharge from the relief valve. This discharge is a
visual indication that the valve needs cleaning or repair. In addition, it is rec-
ommended that periodic testing of the valve be done in compliance with local
codes to ensure its proper operation.
The relief vent discharges water during no-flow periods when:
(1) the first check valve is fouled; or
(2) the inlet pressure to the check valve drops sufficiently due to upstream pres-
sure fluctuations. This affects the required operating differential between the
inlet pressure and the reduced pressure zone; or
(3) the second check is fouled during emergency backflow or resulting from a
water hammer condition.
For troubleshooting guide send for literature S-TSG.
NOTE: When installing the Series 919 and LF919 on fire prevention systems,
special considerations are required.
Fire Protection System Installations: The National Fire Protection Agency (NFPA)
Guidelines require a confirming flow test be conducted by a certified tester when-
ever a “main line” valve is installed, such as a shutoff valve or a backflow preventer.
Installation Instructions
Series 919 and LF919
1 ⁄
4
" – 2" (8 – 50mm)
1/2"
3/4" M2
1" 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
A. Shutoff Valves: If you remove the shutoff valves from the Series 919 and LF919, reassemble
the shutoff valve with the test cock mounted on the inlet side of the unit.
B. Always install the Series 919 and LF919 in an accessible location to facilitate testing and
servicing (See Page 2). *Check the state and local codes to ensure that you install
the backflow preventer in compliance with those codes, such as the proper height
above the ground.
C. It is recommended that you install a strainer ahead of the Series 919 assemblies to protect
the internal components from unnecessary fouling.
CAUTION:
Do not install a Series 919 and LF919 with a strainer in rarely used water lines, such as a fire
sprinkler system which is only used during emergencies.
Start Up: Close the downstream shutoff. Open the upstream slowly and fill the valve. When the
valve is filled, open the downstream shutoff slowly, and fill the water supply system. This is nec-
essary to avoid water hammer and/or shock damage.
D. Vent the air gap and drain line from the relief valve in accordance with code requirements.
Terminate discharge approximately 12" (300mm) above the ground or through an air gap
piped to a floor drain.
45
40
35
30
25
20
15
10
5
0
0 10 20 30 40 50 60 70 80 90 100 110
Flow Rate gpm
Flow Rate gpm
Zone Pressure psi
0 10 20 30 40 50 60 70 80 90 100 110
Zone Pressure psi
1 ⁄
4
" – 1" (8 – 25mm) 919 and LF919
Watts 1 ⁄
4
" – 2" 919
*Vertical Flow Down
1 1 ⁄
4
" – 2" (32 – 50mm) 919 and LF919
350
300
250
200
150
100
50
0
Floor Drain
Air
Gap
Elbow
Strainer
(32 – 40mm) (50mm)
1 ⁄
4
"– 1 ⁄
2
" c 3 ⁄
4
" X 1"
(8 – 15mm) (20mm) (25mm)
0 1 1 ⁄
4
"–1 1 ⁄
2
" 2"
Figure 1