Backflows
Backflows seem to be one of the most controversial components of a sprinkler
system. Many customers think that a backflow device is a needless expense,
hassle, or way to generate revenue for the city and the backflow inspectors.
Truth be known, the backflow is most likely one of the most important
components in the sprinkler system especially on any sprinkler system that uses
a well or a municipal water supply.
There are three main types of backflows used on sprinkler systems. The first
and most common found on residential and commercial sprinkler systems is the
Pressure Vacuum Breaker or (PVB) backflow. The PVB is a very reliable backflow
that usually requires very little service or maintenance besides its annual
inspections. The PVB is a high hazard device that only protects against back
siphonage and not back pressure and it must be installed 12" above the
highest outlet of water on the sprinkler system to perform properly.
The next type of backflow is a (RP) or Reduced Pressure backflow. The RP
backflow is also a high hazard device that is usually used when a property has
extreme elevation changes or building code requires this type of backflow. The
RP backflow protects against back siphonage and back pressure. The main
downfall to this device is maintenance and the fact that the water pressure
loss can exceed 19-20 (psi). This device can be mounted at any height so is
often the choice when there is extreme elevation changes on a property.
The last type of backflow is a double check. This device is no longer
acceptable in central Ohio
because it is a low hazard device but is honorably mentioned because they are
still in use in other parts of the country.
The backflow when properly installed acts as a one way valve allowing water
to enter the sprinkler system but contaminated water cannot return to the water
supply under a back siphonage or back pressure situation. These conditions can
be caused by water main breaks, water main temporary shut downs during repairs
and water service line overloads which usually go unnoticed by a resident and
are more common than most people think.
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