Standpipes are considered either:

Standpipes are classified based on their operational characteristics, which relate to whether they contain water at all times or only when needed. Wet standpipes are always filled with water and are used to provide immediate water availability for manual firefighting efforts. This can be beneficial in enhancing safety and response times during a fire emergency. In contrast, dry standpipes are empty and have pipes that are pressurized to deliver water only when needed. They serve buildings where water weight would be a concern or where freeze protection is necessary.

The classification into wet or dry is an essential part of understanding standpipe systems, as it directly impacts firefighting strategies, equipment selection, and building codes. The other classifications do not accurately represent how standpipes function in fire protection systems; while there may be other classifications relevant in certain contexts, they do not pertain specifically to the operational characteristics of standpipe systems.