Which system contains only air and requires water to be supplied by the fire department through the FDC?

• A. Dry Standpipes
• B. Wet Standpipes
• C. Deluge Systems
• D. Automatic Sprinklers

Answer: (A)

Dry standpipe systems keep the piping filled with air (or another inert gas) and not with water, so the lines are pressurized but dry until water is supplied from an outside source. The water is brought in through the Fire Department Connection (FDC) and charged into the system by arriving fire apparatus, delivering water to the outlets when needed. This setup is why the system “contains only air” until the FDC is used.

Wet standpipes, by contrast, have water-filled piping ready to deliver water immediately, and deluge systems feed water to all open heads, not just through a charge via the FDC. Automatic sprinklers refer to systems that have water distributed through piping and sprinkler heads automatically, not a dry, air-filled network awaiting external water.