Which system uses automatic sprinklers or nozzles attached to a piping system containing air that might be under pressure, with a supplemental detection system installed in the same area as the sprinklers?

• A. Foam-water Deluge System
• B. Foam-water Spray System
• C. Foam-water Preaction System
• D. Foam-water Dry Pipe System

Answer: (C)

Foam-water preaction systems are designed to prevent accidental discharge by using a detection system in the same area as the sprinklers and by keeping the piping charged with air or an inert gas until a detection event occurs. The sprinklers or foam-nozzles are connected to piping that isn’t filled with water initially; when the supplemental detection system is activated (such as by heat or smoke in that area), a valve is released and water with foam concentrate flows into the piping and out through the sprinklers. This combination of air-filled piping and a local detection-triggered release is what defines a foam-water preaction system.

The other options don’t fit this scenario. Deluge systems have piping filled with water (or foam-water) and all sprinklers are open, with no prior detection signal required. Foam-water spray systems are designed for spraying patterns without the preaction logic. Foam-water dry-pipe systems do involve air in the piping, but water is released into the pipes by a dry-pipe valve rather than by a detection system located in the same area as the sprinklers. The presence of a local detection system that must be activated before water enters the piping is the distinguishing feature of a preaction setup.