Backflow incidents have been documented by the University of Southern California Foundation for Cross Connection Control and Hydraulic Research as early as 1903. Click here for link to Pacific Northwest Section of AWWA backflow incidents http://www.abpa.org/incidents.htm
From the Federal Safe Water Drinking Act, the Washington State Department of Health Drinking Water Regulations require the purveyor of water to develop and implement a cross connection control program using the manual published by the PNW Section - AWWA. The scope and complexity of the program is directly related to the size of the system.
The City of Kennewick monitors and controls over 1,800 backflow prevention methods that protect the potable water system. One of the tasks of the Cross Connect Program is to routinely inspect irrigation systems and commercial buildings to identify potential and actual cross connections. Another task of the program is to advise the owners on how to properly eliminate or control the cross connection using the most cost effective methods. The water customer is required to ensure that these devices are operated, maintained, and tested in accordance with the City's Cross Connection Control Regulations
An air gap is considered the maximum protection available against backpressure backflow or backsiphonage, but is not always practical and can easily be bypassed.
A DCVA is effective against backpressure backflow and backsiphonage but should be used to isolate only non-health hazards.
A PVB is a mechanical backflow preventer that consists of an independently acting, spring-loaded check valve and an independently acting, spring-loaded air inlet valve on the discharge side of the check valve.
An RPBA is effective against backpressure backflow and backsiphonage and may be used to isolate health or non-health hazards.