A vacuum breaker is installed between equipment and a steam trap to

• A. Prevent condensate from draining after the steam has been shut off.
• B. Allow condensate to drain after the steam has been shut off.
• C. Trip on low pressure cutoff.
• D. Allow a vacuum to be pulled on the system.

Answer: (B)

Preventing a vacuum in the condensate return path so it can drain after steam is shut off. A vacuum breaker senses falling pressure and opens to admit atmospheric air, breaking any vacuum that would resist condensate drainage. With the vacuum released, condensate can flow freely to the trap and return line once the steam supply is turned off. This is why the device is placed between equipment and the steam trap—to ensure drainage continues smoothly after shutdown. It doesn’t prevent drainage itself, it doesn’t trip a low‑pressure control, and it doesn’t create a vacuum; it stops a vacuum from forming.