The LWF Blog
Facilities Management & Fire Safety – Fire & Rescue Service Facilities – Part 5December 14, 2017 4:05 pm
In LWF’s blog series for those who work in Facilities Management or who have an interest in or responsibility for fire safety, we have been looking at the facilities required by the Fire and Rescue Service in case of a fire at your premises. As has been established in the previous parts of this series, many of these provisions are physical and should be taken into account when the building is at the design and construction phase. In Part 4, lift installations and arrangements for access were both discussed and in Part 5, rising and falling mains will be the subject of our attention.
It would be most difficult and time-consuming for the Fire Service to drag a hose up to the higher floors of a tall building and the same applies to subterranean buildings where the depth of the building is a consideration. For this reason, fire mains are provided in tall or deep buildings.
A dry fire main comprises an inlet which is outside the building, to which the Fire Service connect a hose from a hydrant which pumps water into the pipework of the rising or falling mains system. Inside the building, there are outlets for the water called landing valves on each floor. Firefighters will take hoses of an appropriate length into the building (which are easier to transport while not charged with water) and attach them to the landing valves, enabling them to source water to tackle the fire.
They are known as dry rising mains and dry falling mains because the water is not constantly sitting in the pipework ready to be used, it has to be connected to a water source at the time of the fire. Additionally, a rising mains system is used to serve the upper floors of a tall building and a falling mains system to serve the lower floors and basement floors of a building below ground level.
While a rising dry mains is suitable for moderately tall buildings, in the case of some very high buildings, the rising mains are permanently charged with water by pumps within the building. These are known as wet rising mains will be used where it is established that the time taken to pump water up to the upper floors would be impractically long or unachievable by a standard fire engine pump.
In most commercial buildings, the landing valves are to be found in fire-fighting lobbies, although in residential buildings, a protected corridor area can be considered a fire-fighting lobby for this and other firefighting purposes.
BS 9990 states that where water mains are required, dry rising mains are the recommendation for buildings where floors do not exceed 50m above fire-fighting access level. Anything above this should use a wet rising mains. It also gives information on the size of the pipework and the amount of water it should be able to supply during a given period. For a wet rising main, for instance, this means that a standard water supply will be insufficient and a tank of at least 45,000 litres must be available and not used for any other purpose.
BS 9990:2015 gives recommendations and good practice in matters affecting the design, installation, testing and maintenance of such systems including wet and dry fire-fighting mains.
Dry Rising and falling mains should be inspected every six months and annually, the system should be charged with water to check for leaks. Wet rising and falling mains should be maintained as per BS 9990.
In Part 6, LWF will move on to discuss Foam Inlets and Private Water Supplies. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.
Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.
While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.