A vacuum breaker will prevent the boiler from flooding as a result of the steam condensing internally and creating a vacuum after boiler shut down. The breaker allows air to enter the shell, breaking the intense vacuum. This system is a must for boilers connected to a condensate return tank. The vacuum breaker consists of a spring loaded disc and associated piping and is factory plumbed to the boiler. System ES89369 is a heavy duty system compatible for use on ES boilers. Specify SSB89369 for SSB boilers with stainless steel construction. Specify SVS89369 for SVS boilers.