What characterizes a dry standpipe system?

A dry standpipe system is characterized primarily by its operation. It does not contain water at all times, which distinguishes it from wet standpipe systems. Instead, a dry standpipe is a type of system that remains empty until it is needed, where water is only introduced during operation.

This means that when firefighters or personnel connect to the standpipe, they would typically activate an external water source, such as a fire engine or another water supply, to fill the system and enable water flow for firefighting operations. This ensures that the system remains free of standing water, reducing risks associated with freezing temperatures or water stagnation.

In this context, the option that states it utilizes water only during operation accurately captures the essence of a dry standpipe system, highlighting its unique feature among different types of standpipe systems.