Sometimes the hazard requires a lot of water over a large area all at once. Sometimes the end user wants assurances that the system really needs to start spraying water. Deluge and preaction systems are special systems designed for specific applications that permit end users just such options.
Deluge systems have open sprinklers or spray nozzles and are used where it is desirable to discharge water through all of the system’s sprinklers or nozzles simultaneously. Prior to discharge, there is no water in the sprinkler piping. The water supply is held back by a control valve that is operated manually or automatically by the actuation of a fire detection system.
Preaction sprinkler systems are equipped with automatic sprinklers and are used where it is important to prevent the accidental discharge of water. These systems may also be used where an alarm is desired in advance of sprinkler operation or where it is desired to minimize the water delivery delay inherent in a standard dry-pipe system. Except for the addition of a single check valve and the use of automatic sprinklers, components of preaction sprinkler systems are similar to those of deluge sprinkler systems.
FM Approved deluge and preaction systems are tested to determine performance should they be needed.