WattsBox Insulated Enclosures
For more information, download ES-WB.
Min.
12"
ASSE Approved for vertical installation
flow up and down
3
For indoor installations, the valve must be easily accessible
to facilitate testing and servicing. The assembly may be
installed either vertically or horizontally. If it is located in a
line close to wall, be sure the test cocks are easily acces-
sible. A drain line and air gap should be piped from the relief
valve connection as shown, where evidence of discharge
is clearly visible and so that water damage can be limited.
Therefore, never install the assembly in concealed locations.
NOTICE
Test cock must be located on the first or inlet shutoff valve.
For more information on the air gap, download ES-AG/EL/TC
at watts.com.
Flow
Relief Valve
Below First Check
Valve
Air In
Water
Out
Main
▼
Min.
4
1
⁄
2
"
▼
▼
Air
Gap
First
Check
Valve
LF909QT-S
Vertical Installation - Upward Flow
In an area where freezing conditions do not occur, the assembly
can be installed outside of a building. The most satisfactory installa-
tion is above ground; install in this manner whenever possible.
In an area where freezing conditions can occur, the assembly
should be installed above ground in an insulated enclosure.
The assembly may be installed in a vertical or horizontal line and in
an accessible location to facilitate testing and servicing. A discharge
line should be piped from the air gap at the relief valve connection
making sure there is adequate drainage. Never pipe the discharge
line directly into a drainage ditch, sewer, or sump. The assembly
should never be installed where any part of the unit could become
submerged in standing water. Consideration should be given to the
installation of external support structure as applicable.
In general, the installation of backflow preventers into pits is not rec-
ommended. This type of installation should occur only when abso-
lutely necessary and then only when approved by local codes. In
such cases, a modified pit installation is preferred.
Two or more smaller size valves can be piped in parallel (when
approved) to serve a larger supply pipe main. This type of installa-
tion is employed where increased capacity is needed beyond that pro-
vided by a single valve and permits testing or servicing of an individ-
ual valve without shutting down the complete line.
The number of valves used in parallel should be determined by the
judgment of the compliance engineer based on the operating conditions
of a specific installation.
The following table shows the total capacity provided with dual valve
installations of various sizes.
Indoors
Outside Building Above Ground
Parallel
LF909S
LF909QT-S
Air Gap
(Drawings not to scale)
CAPACITY REQUIRED FOR SYSTEM
50 gpm
100 gpm
150 gpm
200 gpm
250 gpm
350 gpm
Two
3
⁄
4
"
Two 1"
Two 1
1
⁄
4
"
Two 1
1
⁄
2
"
Two 1
1
⁄
2
"
Two 2"
Devices
Devices
Devices
Devices
Devices
Devices
NOTICE
Consult local codes for approval.
