hospitals fire hydrants

[potter 2]

Im just looking at the national guidance document for the provision of fire fighting water .It talks about 35lps a hydrant for "large health" premises.What size does that start at.I can find in the old  htm 81 reference to "small detatched hospitals...detatched,,less than 1000 smts..no patient above second...max 30 patients. Is it a case that if its not small,,it must be large so I apply 35lps of water thrugh a hydrant.Do you know if fire authorities have been rigid on the flow when the water board cant gaurantee the required flow,,any thoughts

[kurnal]

Hydrants are always a problem these days. 35lps equates to about 2100litres per minute. The British standard for fire hydrants BS750 IIRC is 2000l/min at a running pressure of 1.8 Bar ( please anyone correct this if I am wrong)
Thre are also recommendations in respect of proximity of hydrants to the building but I dont think there is anything set down as to how many hydrants must be able to operate  at once.

So the document you are looking at is basically seeking the equivalent of a BS hydrant.
Cant help you specifically on definitions of what is a large or small hospital. I would suggest a common sense approach such as all access points that may be used by firefighters in an emergency should have a hydrant within 90m of the fire service access point.

But it is very doubtful that you will be able to get any assurance from the water company over flows of this size. They are fearful of their legal obligations to maintain delivery and quality of water to their domestic customers and the regulator will fine them if they fail to meet this. The best approach- and one they will support- is to provide a water storage facility on site to supplement the fire hydrants- say at least 65000litres. If you undertake to do this, they will most likely agree to the installation of hydrants and whilst they will not guarantee any flow performance you will probably be very surprised how well they perform. All this from recent experience but in an industrial setting. We provided 400,000 litres of stored water for the same reason and the hydrants are so good that the pressure just about bends the standpipe (Not that we have tried of course)

[John Webb]

Strictly speaking the flow of 2000 lpm at a maximum of 1.8bar in the BS 750 is a test of the resistance of the hydrant to water flow, and sluice-valve hydrants in particular will often allow greater flows for that pressure - or flow 2000 lpm with much less pressure loss from mains pipe to standpipe outlet.
It is customary when feeding a fire pump from a hydrant not to let the pressure at the inlet to the pump drop much below 1bar - this ensures that the pump is not trying to take more out of the hydrant than the hydrant can supply. So theoretically you should allow a minimum pressure in the mains of 2.8 bar (1+1.8 bar) when the flow is at a maximum.

kurnal - I presume you have a pump supplying the hydrants from the storage tank in the arrangement you cite?

[kurnal]

No John
Its just a static tank with fire service female suction outlets for the fire brigade to pump from, filled by trickle ballcock from the mains supply at the maximum rate the water company would allow. It took rather a long time to fill. Not ideal but the alternative was to leave the site as derelict land and site the enterprise elsewhere.  The building is also fully sprinklered and the fire fighting tank sits alongside the sprinkler tanks.
The water company would not install hydrants unless there was an alternative supply of water on site. In the event the hydrants, which are fed from the public main perform far better than ever predicted- the tank isnt really needed though who knows what the future holds.

[John Webb]

Thanks, kurnal. I just hadn't got clear in my mind if the tank was directly connected to the hydrants or what. Your information makes things clear.
Talking about high pressure on a mains, I once attended a furniture factory fire in High Wycombe which 3 sprinkler heads had sucessfully extinguished; the static pressure on the system directly connected to the mains was around 120-130 psi because High Wycombe is supplied by reservoirs sited on the surrounding hills!

[Colin Newman]

In response to the original post, the 35lps is detailed in the "National guidance document on the provision of water for fire fighting" that was published jointly by the Local Government Association and Water UK in 2002.  My reading of the guidance on flow rates given in Appendix 5 is that 35lps is appropriate for any healthcare facility larger than a single storey health centre.  However, with the increasing development of community treatment centres, many of which are multi-storey, I take into account the other exmaples given in the appendix and compare the size of the development, the vulnerability of the occupants etc. to determine the appropriate fire fighting water provision.

I've found that largely both the fire authorities and the water companies are ignorant of the national guidance document despite their representative bodies having published it.  Even the LGA wasn't aware of it when I contacted them earlier this year, although they did eventually agree that the document was current.

I've had experience of at least one fire authority insisting that 35lps was provided on a hospital PFI even though the water company would only guarantee 25lps.  I've also known a water company to agree to upgrade their supply to meet the guidance once they realise that the guidance has been published jointly with Water UK.

[John Webb]

Colin,
Thanks for pointing out the LGA/Water UK document. Is it available to download at all?

[Tom Sutton]

Try http://admin.evolvingmedia.co.uk/users/files/0National_guidance_document.pdf

[John Webb]

Many thanks!