Above ground fire hydrants

[akmac]

Does anyone know if it is a requirement for hydrants in the UK to be below ground type ?  Scottish Building Regs at least seem to specify them.  The insurance company I work for prefers above ground types, obviously with UK style hose fittings.  They are a bit harder to park on top of or lose in a flower bed.  In at least one part of Scotland we are being told they are not acceptable.  Are there advantages to below ground hydrants ?

[Chris Houston]

This is nothing but pure speculation, but I suspect below ground types are less prone to vehicular impact or malicious damage.

[kurnal]

We used to be told that it was to protect them from frost damage.
I never really believed this because it doesnt seem to be a problem in New York where winters are harder than ours.
In high risk private installations they are often above ground.

[John Webb]

My understanding of the differences when comparing the USA and British fire hydrants comes from past reading of American fire journals. The main reasons for the USA having above ground hydrants is for faster location, particularly when snow has fallen, and the large diameter pipework allows much higher flowrates - needed in the USA because of the much greater use of timber construction in houses. The USA hydrants are not filled with water in the vertical column above ground until the (underground) valve is turned on, so the potential for frost damage is limited. But the USA hydrant is more susceptible to impact damage and misuse.
The UK style is less prone to these last two factors, althought I have seen a standpipe bent where an unobservant driver has run into it. But of course hydrants are less easy to find in snowy weather. Bearing in mind most UK fires are dealt with by using hosereels and the water in the appliance tank, its seems a matter of 'horses for courses', perhaps.
Some larger industrial sites are fitted with their own ring mains, permanent hydrants etc., but such a system can be rendered unusable by an on-site incident as happened at Flixborough and Buntsfield.

It is probably easier on an industrial site to deter people from parking close to an above-ground hydrant, and to protect the hydrant against accidental impact damage. Back to what your Fire Risk Assessment says about your particular site, perhaps?

[akmac]

Thanks for the comments.  Like I said, we prefer above ground though it is not critical.  What suprised me was the fire brigade/building control in a part of Scotland insisting a site rip out its above ground hydrants and replace them with below ground.  By the letter of  the building codes they seem to be correct as the Scottish regs specify hydrants to BS750.  I don't currently have a copy of it but its title is "Underground Fire Hydrants..." which suggests it does not cover above ground models.  Interestingly the English regs. don't specify a design standard for hydrants.

[John Webb]

I confirm that BS750 deals only with underground hydrants. Do the Scottish Regs make any reference to BS5306, Part 1 'Hydrant systems, hose reels and foam inlets'? I don't have a copy of this myself but recall from past reading this does allow permanent above-ground hydrants where the risks involved on a site warrent it.
In the case you mention I must admit I'm a bit surprised that such action should be taken.

[akmac]

I've done some further checks and looks like the actual building regulations do not specify which standard the hydrants are to.  The reference to BS750 is in Scottish Building Services Agency's technical handbook which is a guide to how to meet the regulations.  I guess it means the site mentioned above could appeal and almost certainly win, however it is probably cheaper and certainly quicker to replace the hydrants.  BS5306 part 1 is referred to, but only in regard to dry risers.