Wet Riser & Dry Riser System
Wet risers are a legal requirement in buildings over 50m tall as they provide better water pressure on higher floors than dry riser systems can provide. This is a fairly recent requirement, with pre-2006 legislation requiring wet risers only for buildings of 60m or more.
Wet riser systems are very similar to dry riser systems, although, as the name suggests, the pipe networks are kept constantly full through a pressurised supply. This will be in the form of either a storage tank or the mains. The outlet system across the floors remains the same. However, should a fire break out on higher levels, firefighters will have instant access to pressurised water, rather than water that is simply pumped through the system. Wet risers should, at the minimum, provide 1500 litres of water per minute, for a total of 45 minutes.
Dry risers are a legal requirement in buildings more than 18m tall. They’re typically only used in buildings between 18m and 50m, however, due to limitations in how they operate.
Dry riser pipe networks connect a ground floor inlet (usually an external inlet) with multiple internal outlets located across the higher floors of the building. The pipes are typically dry – hence the name. When needed, water is pumped throughout the network, enabling firefighters to attach their equipment to the closest outlet for an instant source of water. Outlets are usually located within every 900 square meters of floor, and are typically found in lobbies, stairways, and cupboards. The pressure limitations of pumped water mean that dry risers perform best in buildings under 50m, while those over 50m require a wet riser system.
The difference between dry & wet risers
Despite all these similarities, there are some significant differences between the two systems. As a property agent or facilities manager, it’s important to understand how dry & wet riser systems differ.