What is the defining characteristic of a dry standpipe in firefighting operations?

• A. Contains only air; water must be supplied by the fire department through the FDC.
• B. Contains water in the riser and does not require external supply.
• C. Has a built-in pump that pressurizes water.
• D. Is always ready for immediate water flow.

Answer: (A)

At least one specific system feature defines a dry standpipe: the piping that runs vertically is not filled with water. It contains air, and water must be supplied from an external source, typically the fire department through the Fire Department Connection (FDC) or by a pumper charging the system. This setup allows the system to be charged only when needed, and helps prevent freezing and reduces the weight of water-filled piping. Once water is introduced from the outside, the standpipe becomes pressurized and water can flow to the hose outlets.

The other statements don’t fit the defining idea. A system that already contains water in the riser is a wet standpipe and does not require external supply. A built-in pump isn’t what defines a dry standpipe, since the defining trait is the lack of water in the pipes until external supply is provided. Saying it’s always ready for immediate water flow implies water is already in the lines, which isn’t the case in a dry standpipe.