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Cross-connections are found in all plumbing systems. It is important that each cross-connection be identified and evaluated as to the type of back-flow protection required to protect the drinking water supply. Some plumbing fixtures have built-in back-flow protection in the form of a physical air gap. However, most cross connections will need to be controlled through the installation of an approved mechanical back-flow prevention device or assembly. Some common cross-connections found in plumbing and water systems include:

-Wash basins & service sinks

-Hose bibs

-Irrigation sprinkler systems

-Auxiliary water supplies

-Swimming pools/hot tubs

-Photo developing equipment

-Solar heat systems


-Fire sprinkler systems

-Water re-circulating systems


What is Cross-Connection?

Cross-connections exist whenever the drinking water system is or could be connected to any non-potable source (plumbing fixture or equipment used in any plumbing system).  Pollutants or contaminants can enter the safe drinking water system through uncontrolled cross-connection when backflow occurs.

Where are Cross-Connections Found?

Backflow Preventer Assembly Example

Example of how a backflow preventer works

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Both types of backflow preventors are used to prevent backflow of contaminated water into the potable water system:


Reduced-Pressure Backflow Assembly (RPBA) - used for High-risk scenarios and is normally placed above ground and in a building. 


Dual-Check Valve Assembly (DCVA) used for LOW-risk scenarios and is normally berried, only exposing the top. The standard location is near the water meter in a separate box. However, can be located near irrigation controls. 



1.Hose bib vacuum breakers are specifically made for portable hoses (ex: garden hose) attached to threaded faucets. Their purpose is to prevent the flow of contaminated water back into the drinking water supply. These devices are not intended for operation under continuous pressure.
2. Backflow prevention assemblies are mechanical devices installed on water services lines (or at plumbing fixtures) to prevent backflow of contaminants into the drinking water supply through cross-connections.

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