Most buildings use a wet pipe system, but cold spaces, sensitive equipment and some industrial hazards call for something different. Here’s how the main types compare.
Wet pipe
The pipes are full of water at all times. When heat opens a sprinkler, water discharges immediately. Wet systems are the simplest, most reliable and least expensive to maintain — the right choice anywhere the building stays above freezing.
Dry pipe
The pipes hold pressurized air or nitrogen instead of water. When a sprinkler opens, the pressure drops, the dry pipe valve trips and water fills the system. They’re used in unheated warehouses, parking garages, loading docks and freezers. Expect a short delay before water arrives, extra testing and closer attention to corrosion — filling with nitrogen instead of air slows internal corrosion considerably.
Pre-action
Also dry, but water only enters the pipes after a separate detection system — usually smoke or heat detectors — confirms a fire. That second step protects data centers, archives, museums and other spaces where an accidental discharge would be costly. Pre-action systems are the most complex to design and maintain.
Deluge
Every sprinkler is open, so the whole area is flooded as soon as the detection system trips. Deluge systems protect high-hazard areas such as fuel loading racks and some chemical processes, where fire can spread quickly.
| Type | Water in the pipe | Best for | Upkeep |
|---|---|---|---|
| Wet | Always | Heated buildings | Lowest |
| Dry | After a sprinkler opens | Spaces that freeze | Moderate |
| Pre-action | After detection confirms a fire | Sensitive equipment and records | Highest |
| Deluge | After detection; all heads open | High-hazard processes | High |
The right system depends on temperature, occupancy, what’s stored and your insurer’s requirements. We’ll assess the space and recommend the simplest system that meets code.