3
Installation
A. Series 909/LF909 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/LF909 should always be installed in an accessible loca-
tion to facilitate testing and servicing. Check the state and local
codes to insure that the backflow preventer is installed in compli-
ance, such as the proper height above the ground.
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 dis-
charge 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 unnecessary fouling.
E. Backflow preventers should never be placed in pits unless abso-
lutely 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 terminating
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 damage caused by a cat-
astrophic 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 instal-
lation 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 determined by
the engineer’s judgement based on the operating conditions of a
specific installation.
Indoors
Above Ground
Parallel
Now available, WattsBox Insulated Enclosures, for more information, send for ES-WB.
Min. 12” (300mm)
Watts 909/LF909
2
1
⁄
2
" – 10" (65 – 250mm)
Strainer
Air Gap
Watts 909S/LF909S FDA
2
1
⁄
2
” - 10” (65 - 250mm)
Meter
Strainer
Main
Air
Gap
12” (300mm)
support
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
450 GpM
640 GpM
1000 GpM
2000 GpM
3000 GpM
5000 GpM
Two 2
1
⁄
2
"
Two 3"
Two 4"
Two 6"
Two 8"
Two 10"
Devices
Devices
Devices
Devices
Devices
Devices
Table shows total capacity provided with dual valve installations of various sizes.
