Basic Installation Instructions
Series 909
Sizes: 2
1
⁄
2
" – 10" (65 – 250mm)
Installation
A. Series 909 should be installed in a horizontal and
upright position. This positions the relief valve below the
first check valve, enabling the zone to drain through the
relief valve outlet. The shutoff valve with the test cock is to
be mounted on the inlet side of the backflow preventer. The
test cock is on the inlet side of the shutoff valve.
B. The 909 should always be installed in an accessible location
to facilitate testing and servicing. Check the state and local
codes to insure that the backflow preventer is installed in
compliance, such as the proper height above the ground.
C. Water discharge from the relief valve should be vented in
accordance with code requirements. The relief valve should
never be solidly piped into a drainage ditch, sewer or sump.
The discharge should be funneled through a Watts air
gap fitting piped to a floor drain.
D. Watts recommends a strainer be installed ahead of Watts
909 Series assemblies to protect the discs from unnec-
essary fouling.
E. Backflow preventers should never be placed in pits unless
absolutely necessary and then only when and as approved
by local codes. Consult your local or state plumbing or
health inspector. Watts recommends installation indoors or
above ground in an insulated enclosure.
Start Up
F. The downstream shutoff should be closed. Open upstream
slowly, fill the valve and bleed the air through Test cock 2, 3
and 4. When valve is filled, open the downstream shutoff
slowly and fill the water supply system. This is necessary to
avoid water hammer or shock damage.
G. The installation of a Watts air gap with the drain line termi-
nating above a floor drain will handle any normal discharge
or nuisance spitting through the relief valve. However, floor
drain size may need to be designed to prevent water dam-
age caused by a catastrophic failure condition. Do not
reduce the size of the drain line from the air gap fitting.
H. 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 assemblies used in parallel should be deter-
mined by the engineer's judgement based on the operating
conditions of a specific installation.
Indoors
Above Ground
Parallel
TABLE ONE - CAPACITY REQUIRED FOR SYSTEM
50 gpm
100 gpm
150 gpm
200 gpm
250 gpm
350 gpm
450 gpm
640 gpm
1000 gpm
2000 gpm
3000 gpm
5000 gpm
Two
3
⁄
4
"
Two 1"
Two 1
1
⁄
4
"
Two 1
1
⁄
2
"
Two 1
1
⁄
2
"
Two 2"
Two 2
1
⁄
2
"
Two 3"
Two 4"
Two 6"
Two 8"
Two 10"
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Devices
Table shows total capacity provided with dual valve installations of various sizes.
Now available, WattsBox Insulated Enclosures, for more information,
send for ES-WB.
Watts 909S
2
1
⁄
2
" - 10"
(65 - 250mm)
Meter
Strainer
Main
Air
Gap
12" (300mm)
Min. 12" (300mm)
Watts 909
2
1
⁄
2
" – 10"
(65 – 250mm)
Strainer
Air Gap
3
support
