Deluge Sprinkler System
All Sprinklers, All at Once

What Makes Deluge Different

In a wet, dry, or preaction system, sprinklers are closed at the factory by a fusible element. Water only reaches the floor under the one head that got hot enough to fuse. In a deluge system, every sprinkler is open — they are nothing more than brass nozzles with no fusible element at all. The pipe itself is dry, held at atmospheric pressure by a closed deluge valve.

When a detection circuit senses a fire and releases the deluge valve, water floods the entire piping network simultaneously and discharges through every open nozzle at once. A deluge system applies water to the entire protected area rather than targeting a single point of origin. That is the right answer for fuel spill fires, high-challenge hazards, and anything where a single-head attack is too slow or too local.

Where Deluge Is Used

The Deluge Valve

A deluge valve is a large clapper or diaphragm valve that holds back the water supply. It is normally closed, with a small supervisory pressure in the priming chamber. When the detection system signals a release, a pilot solenoid or pneumatic release mechanism vents the priming chamber, the clapper snaps open, and the full water supply rushes into the piping. Once tripped, the valve latches open until manually reset.

Unlike a dry pipe valve, the deluge valve does not use differential air pressure to hold itself shut. Because the system piping is dry at atmospheric pressure, there is nothing pushing the clapper back toward the seat — it is held by a mechanical latch released by the detection system.

Testing and Reset

Deluge valve testing is invasive: the annual trip test under NFPA 25 §13.4.3 requires actually releasing the valve and flowing water through the piping. Full-flow tests are required every 3 years. Because the system discharges into a protected area, test coordination must account for the water that will end up on the hangar floor, transformer pit, or loading rack. Many facilities use a bypass or test-only isolation arrangement to divert flow during testing.

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