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Backflow Preventer to Use
and Why to Use Them!
|In most homes the landscape
irrigation system and the potable water system are one and the
same -- there is no separation. Here's where the danger comes
in. Sprinkler lines lay in gardens and lawns that are often
sprinkled with weed killer, pesticides, and other poisons.
Irrigation systems occasionally draw water inward (backwards).
This phenomenon is known as a siphon or backflow. Backflow can
result in contaminated water at a tap inside the home. Is there
any wonder why the building code requires that all outside
irrigation lines have some sort of anti-siphon protection?
can be defined as the unwanted reverse flow of any liquid,
solid or gas in a piping system. In an irrigation
application, this means that water within the irrigation system
may find its way back into the potable (drinkable) water system
during a backflow incident.
preventer is a device designed to prevent potable
water from being contaminated with non-potable water in the
event a cross-connection exists during a condition of backflow.
There are two main types of
backflow: Back Pressure and Back Siphonage.
pressure is when pressure downstream of the device is
greater than the pressure upstream. Water hammer is an example
Back siphonage occurs when a
vacuum is created upstream and water gets literally sucked
backwards. An open fire hydrant, or water main break can cause
back siphonage. Not all backflow devices are created equal.
the Differences Between each Type of Backflow Preventer and when
to Use Them
Great Graphics and Content!
Why You Should Use
a Blackflow Preventer
and Hydraulic Research
University of Southern California
Prevention Assemblies Protect Against Contamination
by Terry Nelson
These are a must in all sprinkler systems if you want to protect
yourself from physical harm as well as the law. The backflow
preventer prohibits the contamination of your personal water
supply. And while the anti-siphon valve already has such a
stabilizing mechanism built in, the Globe and Angle Valve are
incomplete in such regards. Thus, if you have selected to
install a Globe or Angle Valve, you must also choose one of the
following backflow preventers.
It is Sprinkler Warehouse's recommendation
that you avoid this type of backflow device since it is
If you make this selection, be sure to buy one unit per
control valve located on the landscape. They are the cheapest of
backflow preventers, however, almost all city codes do not allow
the use of this type backflow device for sprinkler systems.
If you have a lot of control valves, specifically 6 or
more, it tends to cost you more in the long run, and a pressure
vacuum breaker becomes the more practical choice. AVBs must be
installed at least 6" above the highest sprinkler head in
the zone that they operate.
Comparable in function to the AVB but only requires the
installation of one breaker for the entire irrigation system.
Accordingly, the number of control valves on your property is
irrelevant. It should be mounted on the mainline leading to all
control valves, 6" above the highest sprinkler head.
This is one of our Best Selling types of
The best that money can buy, this preventer is almost always
found in a commercial sprinkler system and can be a great
compliment to a residential system as well. The device allows
for the application of fertilizers or other chemicals into the
irrigation system, a function that no other preventer performs.
Used mostly in dangerous situations, it should be set up 12"
This preventer allows for the flow of pure water that is not
susceptible to contaminants in the air. Though this device does
not allow for the application of chemicals into the irrigation
system, it is cheaper in comparison to the RPBP. Typically, it
is installed beneath the ground in a vault and sometimes in
basements, a tactic that protects them from freezing.
This is one of our Best Selling types of
backflow devices. It works great when installing the backflow
device in a basement or below grade.
The Problem With Double Check
Though the preventer is built with two check valves, in the
instance that dirt or other objects gets stuck in one valve, it
is likely that the same will happen to the other valve at the
same time. Thus, the two valves could fail at the same time, in
turn causing the water supply to be contaminated by noxious