Fisher offers multiple solutions for backflow prevention. Air Gap allows for a minimum physical separation between the potable supply outlet and the overflow rip. It’s important to maintain a minimum of 2” of Air Gap, Fisher says. An atmospheric vacuum breaker is commonly used on a kettle filler or service sink faucet. It’s designed to prevent pollutants and contaminants from back-siphonage. A backflow preventer is used when the supply outlet may be allowed to reach the overflow rim. This is acceptable for protection of pollutants only. The Anti-Spill Pressure Vacuum Breaker protects against backflow from a non-potable source due to negative supply pressure and is used in continuous pressure applications where shut-off valves are on the inlet side of the system.

Fisher Manufacturing.