Wet pipe
Water in the piping
Commonly discussed for suitable heated spaces.
Understand wet pipe ↗Tool
Four-system comparison
Compare wet, dry, pre-action and deluge concepts side by side, with the questions each raises.
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Dry pipe
Pressurized air or gas in the protected piping
Often discussed where freezing exposure affects the design.
Understand dry pipe ↗Pre-action
Normally no water in the protected piping in common arrangements
Used in selected applications with coordinated detection and release arrangements.
Understand pre-action ↗Deluge
Water held back before the protected distribution piping
Special hazard applications require a specific engineered arrangement.
Understand deluge ↗Concepts vary by exact design and equipment. Pre-action arrangements differ. The illustration does not show valve operation, system adequacy, discharge timing or a suitable design for your building.