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BASIC TYPE OF BACKFLOW PREVENTION DEVICES
Please note:  The following is for information purposes only and does not in anyway mean
these are approved devices.  Check with your local code enforcement office before
selecting your backflow device.

Device Type & Use

Description

Installed

Examples

Illustration

AIR GAP
High or low health hazard, back-siphon protection.
Physical separation of potable and non potable water systems - gap equal to 2 times diameter of supply line. End of supply pipe.  Pesticide spray tanks, sinks, any non-pressurized receiver. 

HOSE CONNECTION VACUUM BREAKERS
Hose outlets, non continuous pressure
Single check valve with atmospheric vacuum breaker vent. Typical size: 3/4 inch hose thread. On hose bibbs and service sinks (no downstream valves).  Hose bibbs, service sinks, hydrants.

ATMOSPHERIC VACUUM BREAKER
High hazard, non continuous pressure or backpressure.
Single float and disk with large atmospheric port. Typical sizes: 1/2 inch to 3 inches. 6 inches above fixture rim, not subject to backpressure or continuous pressure (Back-siphon protection only.) Pesticide spray tanks, single-zone lawn sprinklers, washing machines, dishwashers, processing tanks. 

PRESSURE-TYPE VACUUM BREAKER
High hazard continuous pressure.
Spring-loaded single float with independent first check valve. Shut- off valves and test cocks. Typical sizes: 1/2 inch to 2 inches. 12 inches above overflow level of system being supplied and for continuous supply pressure. (Backsiphon protection only.)  Lawn sprinklers, livestock water systems, pesticide spray tanks and filling systems, swimming pools, laboratory equipment. 

DOUBLE-CHECK WITH INTERMEDIATE VENT 
Low hazard, continuous pressure, small pipes.
Two independent check valves with intermediate vacuum breaker and relief valve. Typical sizes: 1/4 inch to 3/4 inch.  Cross-connections with low health hazards, subject to back-pressure, back siphonage, backflow and continuous pressure.  Small boilers, dairy equipment, residential small cooling towers.

DOUBLE-CHECK VALVE
Low health hazard, continuous pressure. 
Two independent check valves with various arrangements. Typical sizes: 3/4 inch to 10 inches. Cross-connections with low health hazards, subject to continuous pressure. Fire protection sprinklers, tanks and vats, cookers, supply lines.

REDUCED PRESSURE ZONE 
High hazard, continuous pressure and back pressure back-siphon protection.
Two independent check valves with intermediate relief valve. Shut-off valve and test cocks. Typical sizes: 3/4 inch to 10 inches. All cross connections subject to back pressure or back- siphon and high health hazards continuous pressure.  Main supply lines, commercial boilers, hospitals, process tanks, sewage treatment, pesticide handling.


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Copyright 2013 Apex Backflow. All rights reserved.
Last modified: Wednesday January 23, 2013.

Questions or problems regarding this web site should be directed to Dan Simler.