Dry pipes systems are used in unheated buildings, but the valve room must be heated,

• Dry pipe systems are more difficult to design than wet pipe systems and are harder to restore.
• Pipes are not filled with water (but with pressurized gas or air),
• Heat from a fire opens a sprinkler head
• Usually only one or two heads open
• Air pressure drops in the piping and opens a water valve (the dry-pipe valve),
• Water fills the pipes and exits through an open sprinkler head(s

• Pipes in protected space are filled with air or inert gas; an opening sprinkler head, triggers the system by releasing the air or gas, which allows water to flow into the pipes and then out through the open sprinkler head,
• A dry pipe valve keeps pressurized air above the supply water pressure
• The clapper valve has a locking mechanism to keep the clapper open until it is reset, by draining the system, opening the dry pipe valve cover and resetting the lock