What device can be substituted for a commercial vacuum breaker if it is not available?

The reverse swing check valve is designed to prevent backflow in a piping system by allowing water to flow in one direction while automatically closing to stop reverse flow. Unlike a standard check valve that allows reverse flow if pressure drops, the reverse swing check valve provides a tighter seal against backflow, making it suitable for applications where a vacuum breaker is needed.

A commercial vacuum breaker is primarily used to protect against siphoning in a system, and the reverse swing check valve can effectively create a barrier to maintain pressure and prevent suction conditions. This characteristic aligns it closely with the function of a vacuum breaker.

In contrast, the other types of valves listed may not perform adequately for the specific application of protecting against back-siphoning. A ball check valve generally requires a certain amount of pressure to function properly, a spring check valve relies on the pressure difference to close, and a float valve is primarily used for controlling liquid levels rather than preventing backflow in a vacuum situation.