This backflow glossary gives plain-language labels for common terms used in EPA backflow material. For next steps, see cross connection control, RPZ testing, and more guides.
Backflow
Flow into the pipes of a potable water supply from a source other than the intended source.
Backsiphonage
Backflow caused by negative pressure in those pipes.
Backpressure
A backflow condition caused by pressure on the downstream side being higher than the supply side.
Cross-connection
Any actual or potential connection between a drinking water system and another supply or source that could contaminate it.
Air gap
One of the basic means EPA lists against backflow.
Reduced pressure principle assembly
A device that keeps the zone between two checks lower than supply pressure and includes a relief to atmosphere, test cocks, and shutoff valves.
Double check valve assembly
One of the basic means EPA lists against backflow.
Pressure vacuum breaker
A vacuum breaker the EPA manual says may be used under constant pressure, does not protect against backpressure, and is installed higher than the outlet.
Spill resistant vacuum breaker
A vacuum breaker term used in backflow discussions and related EPA material.
Test cock
A small test opening named in the reduced pressure principle assembly description.
Relief valve
A valve that releases to atmosphere in the reduced pressure principle assembly description.
Where to read next
Use device notes to keep field comments with a record, then continue with the glossary-adjacent guides above.
A report in Backflow Record is a record you fill in. It is not a substitute for a licensed tester or for the form your water supplier requires. It does not report an inspection result, and it does not mean a plumbing rule was met.