The LWF Blog

Fire Engineering Design and Risk Assessment – Firefighting & External Water Supplies – Part 26

February 5, 2019 11:45 am

In LWF’s fire engineering blog series for Architects and other interested parties in the building design business, we have been looking at firefighting. In part 25, we looked at how hydrants should be located in relation to the building perimeter and the likely position of a Fire Service pump upon attending a fire at the premises. In part 26, we continue looking at location and also the type of hydrant provided in relation to the amount of time involved in using it.


In an example used in a previous blog, it was shown that a 1000 litre tank on a pumping appliance with a delivery flow of 160 litres/minute would be exhausted of its water supply within 6 minutes. It stands to reason that with an increased flow rate and the set-up time involved, it can be necessary for an additional supply of water to be provided within 3 minutes. It is likely that one firefighter will be available to set up the additional water supply.


Bearing those estimations in mind, it is important that the hydrant provided is as easily accessed and utilised as possible. Pillar hydrants with instantaneous couplings are available which greatly decrease the amount of time taken to switch from the fire appliance to the hydrant and the new flow of water to be in use. The alternatives – pillar hydrants with screw connections and underground hydrants, both take far longer for a single firefighter to connect to the hose.


The process for accessing an underground hydrant would be as follows:


The firefighter takes a standpipe, key and bar from a locker on the pump, goes back to the hydrant and lifts the pit lid. He takes off the blank cap from the outlet and screws the standpipe onto the outlet. The key is fitted into the false spindle and the bar is fitted into the key. The water is turned on to flush the hydrant and then turned off. Then the firefighter must return to the pump and collect a hose length and return to connect the hose to the standpipe, then back to the pump to pay out the hose and then back to the standpipe and turn on the water. If it is assumed that the appliance is parked 20 metres from the hydrant (one hose length) then the estimated time taken to prime the underground hydrant is 2 minutes.


In part 27 of this series, LWF will continue looking at the placement and use of hydrants. 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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