combined dry-pipe/preaction system
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A system (usually automatic) for protection against fire which, when activated, sprays water over a large area in a systematic pattern; an integrated system of overhead and underground piping, designed in accordance with fire protection engineering standards, which includes: (a) one or more automatic water supplies, (b) a network of specially sized or hydraulically designed piping which is installed (generally overhead) throughout the building or area, (c) sprinklers (i.e., sprinkler heads) distributed in a systematic pattern which are attached to the piping, (d) a valve which controls each system riser or its supply piping, and (e) a device for actuating an alarm when the system is in operation.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.