Broken Vacuum Breaker . If this happens without a vacuum breaker, the sudden reduction in pressure can damage or even collapse. 15mm (1/2″) • bsp threaded. Install Vacuum Breaker • VacuumCleaness from vacuumcleaness.info The ability of a vacuum circuit breaker to break short circuits is pretty impressive since free electrons cannot exist in the presence of a vacuum. There are many instances when a vacuum can be created inside a steam piping system, for example during steam condensation. Vacuum is defined as any medium with a pressure lower than the atmosphere, which is 760 mm hg.