The LWF Blog

Fire Engineering Design and Risk Assessment – Firefighting & The Fire Service – Part 20

December 28, 2018 12:16 pm

In LWF’s Fire Engineering blog series for Architects and others in the building design business, we have been looking at the subject of firefighting. In part 19, the type of equipment used by the Fire Service was discussed and in part 20, we continue from that point before beginning to look at the external water supplies which may be needed for firefighting.


The progress which can be made by one firefighting crew and the amount of time they can work for are determined by a number of limiting factors, as follows:


 The total length of the hose available

 The quantity of water carried

 The availability of additional water from hydrants

 The ability to create safe working practices with limited crew

 The duration of breathing apparatus sets


The strategies and plans of the Fire Service assume that a single pump and crew can deploy one hose. If the layout of the building or breaches in elements of structure will need more than one stopping jet, the number of pumps and crews attending should be sufficient to act before structural integrity is damaged.


It should be noted that a suitably qualified fire engineer, in consultation with building designers, the Fire Service and other relevant parties, can undertake calculations of potential fire size and load in order to help predict the number of fire pumps that might be required in case of a fire.


External water supplies for firefighting


There are various guidance documents in which the use of external water supplies for firefighting is discussed and in some instances, a private water hydrant is required. This is a fairly uncommon occurrence, however, the provision of water supplies for fire-fighting is part of the Building Regulation Requirements, stipulated in Approved Document B.


A water pump can carry between 1000 and 2000 litres in its tank. Depending upon which nozzle, hose type and bar nozzle pressure is used, delivery of water could be anywhere between 160 and 750 litres of water per minute. As the pump carries its own supply of water, there will be little delay in water being applied to the fire. In the case of a 1000 litre water tank and delivery of 160 litres per minute, the water supply would be exhausted in 6 minutes.


When planning for a fire emergency, those figures can be used to determine if it would be advisable to provide a water supply on site. If the fire is unlikely to be extinguished within 6 minutes, it is important to have a further supply so that the firefighting process is not interrupted.


In part 21 of this series, LWF will continue to look at firefighting water supplies. 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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