Backflow: the flow of any foreign liquids, gases, or substances into the distributing pipe lines of a potable supply of water. Backflow may occur under two conditions--pressure greater than atmospheric, and pressure that is sub atmospheric.


Backpressure: backflow caused by a pump, elevated tank, boiler, or other means that could create pressure within the system greater than the supply pressure.


Backsiphonage: a form of backflow due to a negative or subatmospheric pressure within a water system.


Cross-Connection: any connection or structural arrangement between a public or a consumer's potable-water system and any nonpotable source or system through which backflow can occur. (Bypass arrangements, jumper connections, removable sections, swivel or change-over devices, and other temporary or permanent devices through which, or because of which, backflow can occur are considered to be cross-connections.)


Double Check Detector Assembly: Protects potable water systems from a pollutant caused by a cross-connection on a fire system and also detects any unauthorized use of water and leaks on the fire line system. Only used on a backpressure condition. Consists of two independently operating check valves, two shut off valves, and bypass assembly with meter. Used in low hazard conditions.


Double Check Valve Assembly: Protects the potable water supply from a pollutant caused by a cross-connection. Only used in a backpressure condition. Consists of two independently operating check valves, two shut-off valves, and four test cocks. Used in low hazard conditions.


Reduced Pressure Detector Assembly: Protects the potable water supply from contamination caused by a cross-connection on a fire system and also detects any unauthorized use of water and leaks on a fire line water system. May be used on a backsiphonage and backpressure condition. Consists of two independently operating check valves, a hydraulically operated mechanical pressure differential relief valve located between the check valves and below the first check, two shut-off valves, bypass assembly with small diameter RP and meter, and appropriate test checks. Used in high hazard conditions.


Reduced Pressure Zone Assembly: Protects the potable water supply from contamination caused by a cross-connection. May be used on a backsiphonage and backpressure condition. Consists of two independently operating check valves, a hydraulically operated mechanical pressure differential relief valve located between the check valves and below the first check, two shut-off valves, and appropriate test checks. Used in high hazard conditions.