In which type of standpipe system is water typically not present until a fire occurs?

A dry standpipe system is specifically designed to have no water in the pipes until it is needed during a fire emergency. This type of system relies on fire department personnel to connect hoses to external water sources when responding to a fire. The absence of water at all times helps prevent issues related to freezing in colder climates and reduces maintenance hazards.

Wet standpipe systems, in contrast, are filled with water at all times, providing immediate accessibility for fire protection. Standpipe Class I systems are intended for use by professional firefighters and typically involve larger diameter connections. Standpipe Class II systems are designed for trained personnel and provide for smaller diameter connections. While each of these systems serves specific purposes in firefighting, the defining characteristic of a dry standpipe system is that it remains empty until activated by a fire situation.