Wet fire main water supply pipe installed in a building for fire-fighting purposes and permanently charged with water from a pressurized supply, and fitted with landing valves at specified points.
Where fire mains are installed and there are no floors higher than 50 m above fire service access level, wet or dry fire mains may be installed.
Where there are floors higher than 50 m above fire service access level, wet fire mains should be installed owing to the pressures required to provide adequate fire-fighting water supplies at the landing valves at upper floors and also to ensure that water is immediately available at all floor levels.

Dry fire main water supply pipe installed in a building for fire-fighting purposes, fitted with inlet connections at fire service access level and landing valves at specified points, which is normally dry but is capable of being charged with water usually by pumping from fire and rescue service appliances.