- Circular n°465 of December 10, 1951(extract)
This circular specifies that firefighters must have 120 m³ of usable water on the scene of an average disaster at all times, within 2 hours.
It should be noted that the above requirements are only minimums (medium risks) and that, when the risks are significant (saturated residential areas, old buildings, factories, warehouses, theaters, etc.), it is necessary to plan for the simultaneous intervention of several pumping machines. The estimated hourly flow rate required depends on the number of hoses included in the fire department's attack plan.
This objective can be achieved by one of the following principles:
a) A distribution network
"The distribution network is supplied by one or more fire reserves of at least 120 m3,
"The network supplies hydrants or, preferably, hydrants of 100,
"Hydrants must comply with standard NFS 61211,
"Hydrants must comply with standard NFS 61213,
"The flow rate must be at least equal to 60 m3/h under 1 bar of pressure,
" The dynamic pressure must be at least equal to 1 bar,
" Hydrants must be supplied by pipes with a diameter at least equal to their orifice,
" The maximum distance between two hydrants is 400 m,
" The geographical distribution must be refined according to the risks to be defended.
b) Natural water points
"The minimum capacity is 120 m3,
"The natural point is located at a maximum distance of 200 meters from the risk to be defended,
"The suction height must not exceed 6 m,
"Accessibility must be respected in all circumstances,
"A suction area is provided with a minimum surface area of 12 m2 for motor-driven pumps and 32 m2 for heavy machinery,
"Suction areas must be bordered on the water side by an embankment either of solid earth, or preferably of masonry or planks to prevent the machine from falling into the water as a result of a false manoeuvre,
"The possibility is offered of installing a remote suction sump, a dam or a retention basin.
c) Artificial water points
"The minimum capacity is 120 m3 in one piece. In the case of a supply from a distribution network or a spring, a reduction equal to twice the hourly re-supply flow rate may be allowed,
"A judicious location in relation to the risk is to be sought,
"Accessibility must be possible in all circumstances,
"The structure must enable sufficient fire defense against an average risk located within a 200 m radius,
"A 0.80 m manhole with a minimum 0.40 m sump must be provided,
If the layout of the site does not allow access to the pool by fire engines, one or more special outlets or connections of at least 100 mm must be provided at the lower part of the installation.
d) Exceptional cases
Accessory outlets should be installed to complement the reserves. These will enable firefighters to attack a fire before other engines arrive to reinforce it, or to complete their action.
" Case 1: Pipe diameters and hydrant characteristics comply, but the fire reserve is less than 120 m3,
"Case 2: Fire hydrants are 70 mm in diameter with 65 mm connections. Flow must be at least equal to 30 m3 /h with a pressure greater than or equal to 0.6 b.
" Case 3: Fire hydrants are 40 mm diameter with 40 mm connections. The flow rate must be at least equal to 15 m3/h with a pressure greater than or equal to 4 b.