Last edited 15 Aug 2015

Dry riser

Dry risers are used to supply water within buildings for fire-fighting purposes. The provision of a built-in water distribution system means that fire fighters do not need to create their own distribution system in order to fight a fire and it avoids the breaching of fire compartments by running hose lines between them.

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 wet risers, which are permanently charged with water.

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 18m tall. In buildings less than 50m tall, fire mains can be either dry or wet risers, however, where a building extends to more than 50m 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.

Each inlet connector must be within 18m of a fire service appliance access. 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 risers themselves should be within fire-fighting shafts, and where necessary in protected escape stairs. Dry-riser outlets, or landing valves may be located 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 in the dry riser to escape when the riser is charged with water. There is often also a roof-level testing outlet.

Dry risers should be inspected and tested regularly to ensure equipment is functioning correctly and ready for use. Problems can be very serious in the event of a fire, and are typically caused by vandalism or theft, blockages or pipework failure or by connection failure or outlets being open.

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