Dry Risers and wet risers are a system of pipework utilized by the fire brigade to quickly get water in the event of a fire breaking out.
Rising mains in buildings can be either filled with water (Wet Riser) or left dry (Dry Riser). Where mains are supplied from rooftop tanks and pumps in very tall buildings, the mains are referred to as ‘Falling Mains’ or sometimes ‘Down-comers’. The installation of risers removes the need for fire fighters to have to drag charged fire hoses all the way up through tall buildings which could delay fire-fighting operations or create a hazard during evacuation.
Frequently required in high rise buildings dry risers are vertical mains fitted into staircase or lift enclosures or other suitable positions. A dry riser system includes an inlet at ground level on an outside face of the building and outlets (known as landing valves) fitted in cabinets at each floor level, allowing fire and rescue service personnel to pressurize the main from their appliances.
The pipes in dry risers are empty and are only filled with water by fire fighters when they arrive. Fire fighters will connect the pump outlet in one of their appliances to the dry riser inlet. Water is then drawn from the nearest public fire hydrant (fed by the water supplier’s service main) and this is pressurized by the fire pump to provide water at the correct flow and pressure for fire fighting operations at the relevant floor level.
