What is an air gap?
An airgap is an unobstructed vertical distance through the free atmosphere between the lowest opening from any pipe or faucet supplying water to a tank, plumbing fixture, or other device and the flood level rim of the receptacle. This separation must be at least twice the internal diameter of the water supply pipe and never less than one inch. An air gap is considered the maximum protection available against backpressure backflow or back-siphonage but is not always practical and can easily be bypassed.

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1. What is a cross-connection?
2. What is an air gap?
3. What is a reduced pressure zone assembly?
4. What is a double-check valve assembly?
5. What is an atmospheric vacuum breaker?
6. What is a pressure vacuum breaker?
7. What is a hose bibb vacuum breaker?
8. Why do backflow preventers have to be tested periodically?