Atmospheric Vacuum Breaker (AVB)
An AVB is a non-testable mechanical backflow preventer with a gravity opening poppet air opening, designed to admit atmosphere into the downstream sides of the unit under a no flow condition to prevent back siphonage. It must be installed 6-inches above highest downstream water discharge. There shall be no valves or reduction of pipe size on its downstream side.
(Note: This device is installed on certain equipment that uses potable water by the manufacturer or contracted installer. Examples of this equipment are dishwashers, soap dispensers, faucets and deep sinks, etc.). The type of backflow protection required is based on the degree of hazard that the property represents to the potable water supply.
Reduced Pressure (RP) Principle Assemblies
A reduced pressure principle assembly is a mechanical valve assembly that consists of two internally loaded independently operating check valves and a mechanically independent, hydraulically dependent relief valve located between the check valves.
It is used for services that have either health hazards or non-health hazards and under conditions of back pressure or backsiphonage. It provides the highest level of protection among the mechanical backflow prevention devices.
Can you give some examples of cross connections?
- A hose is submerged in polluted or contaminated water
- A secondary source of irrigation water (from a well or pond) is pumped into an irrigation system that is directly connected to the potable water supply system
- A heating boiler with treatment chemical added to prevent internal corrosion is connected directly to the water supply for make-up water
- An underground lawn sprinkler system is directly connected to the water supply system
- A fountain or swimming pool has a direct connection with the water system for filling
In all of these examples, a sudden drop in water pressure could draw contaminants – chemicals, fertilizer, soapy water or even bacteria -- back into your pipes and your drinking water supply. Any of these contaminants could be hazardous to your health if ingested.
The best way to prevent this potential contamination is to eliminate the cross connection. This could mean simply making sure that you never leave a hose submerged in a tub of water or that you never apply fertilizer to your lawn with a hose-aspirator device. In some cases (such as the lawn sprinkling system example noted above) the cross connection cannot be eliminated and the only means of protection is by installation of an approved backflow prevention device.
How do I know if I need a backflow prevention assembly?
Your local plumbing inspector or local licensed plumbing contractor can determine if you have an actual or potential cross-connection and the type of backflow prevention that may be required.