Fire protection piping stays full of water (or air) at all times so that a sprinkler opening over a fire discharges water within seconds. It is designed to NFPA 13 (sprinklers), NFPA 14 (standpipes) and NFPA 20 (fire pumps).
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System types
Type | Pipe holds | Used where |
Wet pipe | Water | Most heated buildings; simplest and most common |
Dry pipe | Compressed air, water held back by a dry-pipe valve | Unheated garages, attics, loading docks |
Preaction | Air; water released only after a detector also trips | Data centers, museums, archives |
Deluge | Open heads; water flows from all at once | Aircraft hangars, fuel and chemical areas |
The city main or fire pump keeps the system pressurized, the fire department can boost it through the FDC, and the riser splits water to each floor's sprinklers and the stair standpipes.