Not every commercial building uses the same type of fire sprinkler system. The choice between wet pipe and dry pipe mostly comes down to one factor: can the space freeze?
Wet Pipe: The Default for Heated Buildings
Wet pipe systems keep water in the piping at all times, so a sprinkler head discharges the moment it activates. They are simpler, less expensive, and the standard choice for offices, retail, hotels, and other heated occupied spaces.
Dry Pipe: For Unheated or Freeze-Prone Spaces
Dry pipe systems hold pressurized air or nitrogen in the piping instead of water. When a head activates, the air releases first, then water fills the pipe and discharges. This added step makes dry systems slightly slower to respond, but it protects against pipes freezing and bursting in spaces like parking garages, loading docks, attics, and cold storage.
Mixed-Use Buildings Often Need Both
It’s common for a single building to use wet pipe throughout heated interior space and dry pipe in an attached unheated garage or loading dock. A fire protection engineer typically maps this out during system design, area by area.
For a full comparison including pre-action and deluge systems, see our Fire Sprinkler System Types guide, or our Code Compliance page for the standards involved.