The LWF Blog

Fire Engineering Design and Risk Assessment – Firefighting & External Water Supplies – Part 21

January 3, 2019 12:40 pm

In LWF’s fire engineering blog series for Architects and others involved in building design we have been looking at firefighting. In part 20, an outline of how the water carried by a fire engine is used with the hoses to provide a limited time supply of water to fight a fire. In part 21, we continue from that point.


As a fire engine can only carry a limited amount of water, a large fire will almost certainly require more water than one engine can deliver. This means that more fire engines may have to be called to the scene, or, in some cases, the fire could be fought successfully by one firefighting team, if access to a hydrant is available.


Approved Document B now requires private hydrants to be installed to new developments if the building has a compartment larger than 280m2 and is erected more than 100 m from an existing water hydrant.


If additional water supplies are to be provided, they should be sufficient to provide water for firefighting in offensive mode.


Fire hydrants are highly effective sources of additional water for the Fire Service, because they are fitted directly to the water mains. There are various national and international standards relating to fire hydrants and water mains, mostly produced by the National Fire Protection Association, based in the US.


NFPA 1: Fire Prevention Code (current edition 2018)  looks at water supply in section 7-5 and refers only to private fire service mains with recommendations that they be installed in accordance with NFPA 24 Standard for the Installation of Private Fire Service Mains and Their Appurtenances.


NFPA 5000: Building Construction and Safety Code (2018) sections 55.8 relating to fire hydrants and 55.9, private fire service mains, both refer to NFPA 24, linked above.


NFPA 24 states the following in relation to the provision of fire hydrants ‘they shall be spaced in accordance with the authority having jurisdiction’ and ‘for average conditions hydrants shall be placed at least 40 feet from the building protected’.


The NFPA Fire Protection Handbook recommends an adequate supply of water at adequate residual pressure as it is the principal agent used to extinguish building fires, in order to fulfil the needs of the fire service and any automatic extinguishing systems.


In part 22 of this series, LWF will continue to look at fire hydrants, the recommendations and any relevant guidances with British Standards. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


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.




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