Now available, WattsBox Insulated Enclosures,
for more information, send for ES-WB or ES-WB-T.
FIBERGLASS WattsBox
Min. 12"
ASSE approved for vertical installation
3
⁄
4
" – 2" flow up and down
3
For indoor installations, it is important that the
valve be easily accessible to facilitate testing and
servicing. Series 909 may be installed either vertically
or horizontally. If it is located in a line close to wall,
be sure the test cocks are easily accessible. A drain
line and air gap should be piped from the relief valve
connection as shown, where evidence of discharge
will be clearly visible and so that water damage
will not occur. Therefore, never install in concealed
locations.
Note:
Test cock must be located on the first or inlet
shutoff valve.
Flow
Relief Valve
Below First
Check Valve
Air In
Water
Out
Main
▼
Min.
4
1
⁄
2
"
▼
▼
Air*
Gap
First
Check
Valve
909QT-S
Vertical Installation - Upward Flow
*For Air Gap information contact your technical
sales representative or refer to ES-AG/EL.
In an area where freezing conditions
do not occur
, Series 909
can be installed outside of a building. The most satisfactory
installation is above ground and should be installed in this
manner whenever possible.
In an area where freezing conditions
can occur
, Series 909
should be installed above ground in an insulated enclosure.
Series 909 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. Series 909 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.
It is generally recommended that backflow preventers never
be placed in pits unless absolutely 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
installation is employed where increased capacity is needed
beyond that provided by a single valve and permits testing
or servicing of an individual valve without shutting down the
complete line.
The number of valves used in parallel should be determined by
the engineer’s judgement based on the operating conditions of
a specific installation.
Table One - 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
Table shows total capacity provided with dual valve installations
of various sizes.
Installation Indoors
Installation - Outside Building Above Ground
Installation - Parallel Consult Local Codes for Approval
909QT-S
909QT-S
Air Gap
(Drawings not to scale)
