Skip to Main Content View Text-Only

Portland Water Bureau

From forest to faucet, we deliver the best drinking water in the world.


1120 SW Fifth Ave, Suite 600, Portland, OR 97204

More Contact Info

Atmospheric Vacuum Breaker

Atmospheric Vacuum Breakers (AVB's) are among the simplest and least expensive mechanical types of backflow prevention assemblies that the end user can buy. AVB's may be purchased at your local hardware store. These assemblies are available in 1/2 inch through 3-inch pipe size and must be installed vertically for proper operation. In addition, the installation must not have shut-offs downstream, and must be installed at least 6 inches higher than any downstream piping.

A diagram of an atmospheric vacuum breaker is illustrated below along with a typical installation:

Standardized Information for Atmospheric Vacuum Breakers:

Installation type:   Above Ground
Safe to inject chemicals into system?   No
Okay to locate control valves downstream?   No
Okay to locate backpressure source downstream of assembly? No
Installation height in relation to highest downstream piping:   6 inches above highest point
Number of assemblies required:   One per zone
Use only with irrigation sprinkler heads?   Yes
Testing required after installation: No
Testing after repairing or moving assembly?   No
Cost:  Least expensive