A Dry Riser is the foremost vertical pipe intended to dispense water to multiple levels of a building as an element of a fire suppression system. Dry risers do not contain water when they are not being used but are charged with water by fire service pumping appliances when necessary. This is as opposed to a wet riser system where the pipes are kept full of water for manual or automatic fire fighting operations.
Dry risers are used to supply water inside buildings for fire-fighting purposes. The facility of a built-in water delivery system means that fire fighters do not need to use their own distribution system in order to fight a fire and it avoids the opening of fire compartments by running hose lines between them.
Dry risers have an inlet connector at rescue service vehicle access level and landing valves at locations on each floor. Part B of the building regulations (Fire Safety) requires that fire mains are provided in buildings that are more than 18 m tall. In buildings less than 50m tall, fire mains can be either dry or wet risers, however, where a building extends to more than 50 m above the rescue service vehicle access level, wet risers are necessary as the pumping pressure required to charge the riser is higher than can be provided by a fire service appliance, and to ensure an immediate supply of water is available at high level.
Inlet connectors are typically contained in accessible, but secure enclosures on the external face of buildings and are identified as a ‘dry riser inlet’. Dry riser outlets, or landing valves, may be in protected lobbies, stairs or enclosures where these are available.
At the top of dry-riser pipework an air valve is provided to allow air into the dry riser to escape when the riser is charged with water. There is often also a roof-level testing outlet. Dry risers are inspected and tested regularly to make sure that the equipment is operating correctly and ready for use.
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