In Germany, VdS CEA 4001 specifies which type of water supply is permissible for firefighting systems. Basically, the amount of water to be stored depends on the risk, the application rate and covered area, and the operating time of the extinguishing system. It must be ensured that the selected water supply is not rendered inoperative or impaired by frost, drought, flooding, or other circumstances. Furthermore, the water must be clean enough to prevent blockages in the piping and nozzles.
There are four options for water supply, and depending on the total area to be protected and the hazard category, one or more of them must be chosen:
- Public water supply system
- Water tank
- Natural and artificial water sources
- Compressed air water tank
Public water supply system
Extinguishing systems may only be supplied directly from the public drinking water network if this is the only source of water. If other water sources are available, the extinguishing system should be connected indirectly. In the case of direct connection to the drinking water network, no extinguishing agent additives such as foam compound may be added to the extinguishing system. The connection requires approval by the water supply company and, if necessary, by the competent authority. In addition, the supply for other consumers must not be impaired by the water extraction for the extinguishing system.
Other important regulations in this area are DIN 1988-600, DIN 14462 and DIN EN 1717. Incorrect connection of firefighting systems to the public drinking water network can have negative effects on drinking water quality, which poses a risk to public health. The fire fighting water must therefore always be safely separated from the drinking water supply system at the fire fighting water transfer point. A free outlet into a storage tank or a separation station are the means of choice here. The DVGW (German Association for Gas and Water) has dealt intensively with this topic and has drawn up specifications for hygienic safety.
One, or a combination of the following devices, can be used for water storage:
- Intermediate container
- Elevated tank
The directive specifies precise requirements regarding the tank design, materials, and strength, and how these must be executed in order to avoid water contamination and deposits.
The minimum water volume is specified for each system. This can either be supplied from a storage tank with the total water supply required, or from an intermediate tank where the total water supply is provided from the water supply in the intermediate tank together with the automatic backfeed. When backfeeding from the public water network, the above-mentioned requirements must also be met.
Natural and artificial water sources
Natural and artificial sources such as rivers, canals, and lakes are considered to be inexhaustible if they can always provide sufficient water capacity due to their volume, climate, etc. It must be possible to extract the required water supply at any time. Whether a water source meets the requirements for the extinguishing system to be installed as well as how the supply from such sources works in detail is very comprehensively regulated in CEA 4001.
Compressed air water tank
A compressed air water tank is a tank that holds water under pressure with air. The air pressure and air volume must be sufficient to deliver all the water at the required water pressure and flow rates.
The choice of water supply
The total area to be protected and the risk dictate how the water supply is to be selected. It also depends on whether the water supply is from a single source, a single source plus increased reliability (for example, use of two or more pumps), or two sources (two simple, independent water supplies).
In individual cases, the ideal solution is worked out together with experts, taking into account the local conditions and protection goals.