Backflow Section Flashcards
Which devices can stop backsiphonage
PVB, DCA, RP and AVB
Which devices can stop backpressure
DCA and RP
Which device can handle constant pressure?
RP, DCA, and PVB
Which device, or devices, are approved when there is chemical applied by aspiration, injection, or emission?
RP
If there is an on-site sewage facility on site, which backflow is approved?
RP
If major maintenance has to be performed, which backflow device has to be properly installed prior to the repair work being performed?
An approved backflow device.
The approved backflow devices for non-health hazards include:
All devices (AVB, PVB, DCA, and RP)
If including a master valve, where does it have to be installed?
Downstream from the PVB, DCA, or RP.
Which devices have to be tested upon installation and annually?
Devices used in applications designed as health hazards.
Which backflow devices have to be tested upon installation?
All backflow devices.
If a DCA is installed below ground, what device is installed?
A Y-strainer installed on inlet side of the DCA.
If there is an additional water source supplying water to a system being supplied by a potable water supply, what device has to used with the potable water supply?
RP
What device cannot be used when there is a health hazard?
DCA
An AVB and PVB can be used in health hazard situations, if the following conditions are not present:
Backpressure
There is a pump downstream
Chemicals added
An atmospheric vacuum breaker (AVB):
Has to be installed 6” higher than the highest head or outlet in the retracted position, will not handle constant pressure, and will stop backsiphonage.
What is the unwanted reversal of water flow in an irrigation system?
Backflow
A cross connection is any actual or potential connection between a potable water supply and:
Any source that has the possibility to introduce polluted or contaminated water back into the potable water that is supplying it.
Backsiphonage is caused by:
Negative or sub-atmospheric pressure.
Backsiphonage can be caused by:
A break in the city main.
The fire department using water from the city fire hydrant to put out a fire.
If the pressure in the sprinkler system (or downstream side) exceed the pressure in the supply side, what phenomenon can occur?
Backpressure
What can cause backpressure?
Gravity or a pump.
How many total ways are there to protect against backpressure and/or backsiphonage?
5
What is the unobstructed vertical distance through free atmosphere between the lowest point of a water supply outlet and the flood level rim of the fixture or assembly into which the outlet discharges?
An air gap
The vertical, physical separation, of an air gap must be:
At least twice the diameter of the water supply outliet, but never less than 1 inch.
What is a typical example of an air gap?
Kitchen sink.
What is the maximum number of hours an AVB can have constant pressure?
12
How high does a pressure vacuum breaker have to be installed?
12” above the highest head or outlet in the retracted position.
How many test cocks does a PVB, DCA, and RP have, respectively?
PVB: 2
DCA: 4
RP: 4
If the highest head a the site is shrub spray on a 12” riser, how high would a PVB have to be installed right next to that head?
24”
Which backflow devices incorporate two check valves?
DC and RP
Which backflow device can be installed below grade (local regulation permitting)?
DC
Which backflow device uses a pressure differential relief valve and has to be installed 12” above grade?
RP
There are two ball valves on which of the following?
DC and RP
The phenomenon that causes water to backflow due to elevation or a pump is called:
Backpressure
