Wet risers are a form of internal hydrant for the fireman to use and are always charged with water. Wet risers are only required for building where the topmost floor is higher than 30.5 meters above the fire appliance access level.
Wet riser system comprises duty fire pumps with standby pump discharging into riser pipe with landing valves at each level and to jet at the fire. A jockey pump is usually provided to maintain system pressure.
A typical wet riser installation is shown as below.