Preaction systems are designed to protect properties in which the danger of serious water damage from premature operation of sprinklers or broken pipes is unusually severe, or those properties which, due to climatic conditions, must otherwise be equipped with a dry system. In a preaction system, the action of a heat-responsive device releases a preaction valve, the water fills the piping system, and an alarm is given in advance of the activation of sprinklers. The alarm often gives an opportunity to extinguish the fire by manual means before a sprinkler activates.
