US Patent 7530402 Water column supervisory switch

A water column supervisory switch having a probe arrangement and probe circuitry for detecting the presence of a conductive medium that has reached a predetermined level above a clapper valve inside a dry pipe valve for a sprinkler system is disclosed. The probe arrangement comprises a housing and a probe operatively associated with probe circuitry that provides a means for activating an alarm when the conductive medium reaches the predetermined level in order for maintenance personnel to drain the water from the dry pipe valve.