What is a dry stand pipe?

Answer 1

A dry standpipe is a system of pipes with fire hose connection outlets inside a building, but it only has water in it when needed, as opposed to a wet standpipe in which water is always present at the hose-connection valves. There may optionally be a hose connected at some of the valve outlets for use by occupants before the fire department arrives with their own hoses.

Water can either be pumped in from a fire department connection (FDC) on the outside of the building, or can be supplied by other pressurized water supply, but in a dry-pipe system, the valve is not opened until water is needed.

An "automatic-dry" standpipe normally contains only pressurized air and valves sensors open the main water valve when the air pressure drops (i.e., someone opens a valve). A "manual-dry" system requires an external source of water and pressure, fed into the FDC. Note that these are not approved under Canadian building and fire codes.

NFPA 14 has more information about the standards for standpipes.