1.
Backflow preventers must be installed in high-visibility
locations in order to allow for immediate notice of telltale
discharge or other malfunction. This location should
also facilitate testing and servicing, and protect against
freezing and vandalism.
2.
Installing a backflow preventer in a pit or vault is not
recommended as flooding of the pit will cause a cross-
connection. Ensure that
all local codes and required
safety provisions are met
. An air gap below the relief port
must be maintained so as to avoid, flooding and sub-
mersion of the assembly, which may lead to a cross-
connection.
3.
A strainer should be installed ahead of the backflow
preventer to protect all internal components from un-
necessary fouling.
CAUTION -
Do not install a strainer ahead of the backflow
preventer on seldom-used, emergency water lines (i.e.
fire sprinkler lines). The strainer mesh could potentially be-
come clogged with debris present in the water and cause
water blockage during an emergency.
4.
Normal discharge and nuisance spitting are accommo-
dated by the use of a Watts air gap fitting and a fabricated
indirect waste line. Floor drains of the same size
MUST
be provided in case of excessive discharge.
5.
When a 909 Series backflow preventer is installed
for dead-end service applications (i.e. boiler feed
lines, cooling tower makeup or other equipment
with periodic flow requirements), discharge from
the relief vent may occur due to water supply
pressure fluctuation during static no-flow condi-
tions. A check valve may be required ahead of the
backflow preventer. *Please see “Troubleshooting”,
page 7,
prior to installation
.
6.
The 909 Series backflow preventer is designed so that
the critical level of the relief valve is positioned below the
first check. This unique feature allows the valve to be
installed either vertically or horizontally
.
7.
Installation procedures must comply with all state
and local codes.
*Please see page 3 for specific in-
stallation procedures.
8.
Prior to installation, thoroughly flush all pipe lines to
remove any foreign matter.
9.
Start up
at Initial Installations and After Servicing: The
downstream shutoff should be closed. Slowly open
upstream shutoff and allow the backflow preventer to
fill slowly. Bleed air at each test cock. When backflow
preventer is filled, slowly open the downstream shutoff
and fill the water supply system. This is necessary to
avoid dislodging O-rings or causing damage to internal
components.
10. Test:
The 909 Series backflow preventer must be tested
by a certified tester at the time of installation in order
to ascertain that the assembly is in full working order
and may be relied upon to protect the safe drinking
water as per applicable standards.
How It Operates
The unique relief valve construction
incorporates two channels: one for air,
one for water. When the relief valve
opens, as in the accompanying air-
in/water-out diagram, the right hand
channel admits air to the top of the
reduced pressure zone, relieving the
zone vacuum. The channel on the left
then drains the zone to atmosphere.
Therefore, if both check valves foul,
and simultaneous negative supply and
positive backpressure develops, the
relief valve uses the air-in/water-out
principle to stop potential backflow.
Repair Parts:
Use only original equipment, manufactured parts
to protect the validated warranty.
First
Check
Relief
Valve
Second
Check
909QT
Reduced
Pressure
Zone
Water Out
Air In
2
Basic Installation Instructions
Watts
3
⁄
4
" – 2" (20-50mm) 909QT High Capacity Relief Series:
Location and Installation Considerations
