any connection between a potable water system and another fluid system through which contamination could enter the potable water system
cross-connection
the flow of any substance back into a potable water system
backflow
a condition in which a system that is cross-connected to a potable water system is at a higher pressure than the water system
backpressure
the condition under which foreign material is drawn into the water system because the system pressure is less than atmospheric pressure
backsiphonage
provides the highest level of protection against backflow
- must be 2 times the inside diameter of the inlet pipe
- minimum gap is 1 in above overflow level
air gap
has two spring loaded check valves
- pressure regulated relief valve between check valves
- can be used on all cross-connections-including high hazard
reduced pressure zone backflow preventer (RPZ)
designed without the relief valve and no external indication of valve failure
-not recommended where failure may result in health hazard
double check valve assemblies
not designed to protect against backpressure
- only used where there is no possibility of backpressure
- installed 6 in above highest point of downstream outlet
atmospheric vacuum breaker (AVB)
not designed to protect against backpressure
- two valve assembly
- installed 12 in above highest point of downstream outlet
pressure vacuum breaker (PVB)
What are the 4 back flow control devices?
1) Air gap
2) Reduced pressure zone back flow preventer (RPZ)
3) Double check Valve
4) Vacuum breakers ( AVB-atmospheric vacuum breaker, (PVB-Pressure vacuum breaker)
