The LWF Blog

Fire Engineering Design and Risk Assessment – Firefighting & External Water Supplies – Part 30

March 4, 2019 3:10 pm

In LWF’s blog Fire Engineering blog series for Architects and others in the building design industry, we have been exploring the subject of firefighting and those matters which should be taken into account for effective firefighting. In part 29, we discussed fire hydrants and required flow. In part 30, we will look at other external water supplies which may be available or necessary.

As a part of a building’s fire safety provision, it may be deemed necessary for a fire tank to be provided and this should be planned at the design stage when the fire protection measures are being decided.  A fire tank is a tank containing water which can be situated either above ground or below, forming part of a hydrant system. When the tank is above ground height it may feed the system through simple gravity and when it is below ground, a suction hose may be used to extract water.

In some cases, the building is situated next to open water suitable for supplying firefighting activities. Such facilities might include the sea, docks, rivers, streams, lakes (natural or man-made), reservoirs, ponds etc. A suction hose will be required in order to extract water.

When considering the capacities required from external water supplies, Approved Document B has the following to say on the subject:

Where no piped water supply is available, or there is insufficient pressure and flow in the water main, or an alternative arrangement is proposed, the alternative source of supply should be provided in accordance with the following recommendations:


(a) a charged static water tank of at least 45 000 litre capacity;


or


(b) a spring, river, canal or pond capable of providing or storing at least 45 000 litres of water at all times of the year, to which access, space and a hard-standing are available for a pumping appliance;


 or


(c) any other means of providing a water supply for firefighting operations considered appropriate by the fire and rescue authority. 

With this in mind, the capacity required is a minimum of 45 000 litres at all times and consultation with the Fire Service in the area must be undertaken.

BS 9999 (https://shop.bsigroup.com/ProductDetail?pid=000000000030357099) states that where the water supply takes the form of a static tank or dam that the capacity should be related to the size of the building and the calculated risk involved. Where there is an unlimited and guaranteed natural water source capable of providing the necessary capacity, there must be sufficient hard standing for fire appliances provided.

In Part 31 of this series, LWF will continue looking at capacities of external water supplies, before looking at the practice of water relay. 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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