The two forms of backflow
BACKPRESSURE
Backpressure backflow is backflow caused by a downstream pressure that is greater than the upstream or supply pressure in a public water system or consumer's potable water system.
Caused by pumps, piping systems elevation, or thermal expansion from a heat source.
BACKSIPHONAGE
Backsiphonage backflow is backflow caused by a vacuum in a public water system.
Usually caused by a loss of pressure in the drinking water system.
Broken public main lines are a possible cause of backsiphonage
The two types of connections
Direct
Indirect
Indirect
Connected directly to the potable water system. Irrigation and fire suppression systems are direct connections.
Indirect
Indirect
Indirect
Indirectly connected to the potable water system. A hose connected to a faucet and laying in a pool, bucket, or sink is an indirect connection.
backflow testing types of backflow prevention
RPZ-Reduced Pressure Zone Assembly
RPZ-Reduced Pressure Zone Assembly
RPZ-Reduced Pressure Zone Assembly
The RPZ backflow assembly is effective against backpressure backflow and backsiphonage and may be used to isolate health or non-health hazards. Backflow testing is done on this assembly using a test gauge
Air Gap
RPZ-Reduced Pressure Zone Assembly
RPZ-Reduced Pressure Zone Assembly
The Air Gap is used to isolate health hazards. An air gap is considered the maximum protection available against backpressure backflow or backsiphonage but is not always practical and can easily be bypassed. Backflow testing is done by visual inspection and measurements
DC-Double Check
RPZ-Reduced Pressure Zone Assembly
PVB-Pressure Vacuum Breaker
A Double Check is effective against backpressure backflow and backsiphonage but should be used to isolate only non-health hazards. Backflow testing is done on this assembly using a test guage
PVB-Pressure Vacuum Breaker
PVB-Pressure Vacuum Breaker
The PVB may be used to isolate health or non-health hazards but is effective against backsiphonage only. Backflow testing is done on this assembly using a test gauge
SVB-Spill Resistant Vacuum Breaker
The SVB may be used to isolate health or non-health hazards but is effective against backsiphonage only. Backflow testing is done on this assembly using a test gauge
HVB-Hose Bibb Vacuum Breaker
The HVB may be used to isolate health hazards but is effective against backsiphonage only and is not for continuous use. The HVB is a device not a backflow assembly, and backflow testing is not done on this device.